Patent Application
20130059036
The present invention relates to the industrial processing of plant-derived food and feed products, especially vegetable oils. The invention may be employed to reduce or eliminate contamination by chlorophyll and chlorophyll derivatives.
Chlorophyll is a green-coloured pigment widely found throughout the plant kingdom. Chlorophyll is essential for photosynthesis and is one of the most abundant organic metal compounds found on earth. Thus many products derived from plants, including foods and feeds, contain significant amounts of chlorophyll.
For example, vegetable oils derived from oilseeds such as soybean, palm or rape seed (canola), cotton seed and peanut oil typically contain some chlorophyll. However the presence of high levels of chlorophyll pigments in vegetable oils is generally undesirable. This is because chlorophyll imparts an undesirable green colour and can induce oxidation of oil during storage, leading to a deterioration of the oil.
Various methods have been employed in order to remove chlorophyll from vegetable oils. Chlorophyll may be removed during many stages of the oil production process, including the seed crushing, oil extraction, degumming, caustic treatment and bleaching steps. However the bleaching step is usually the most significant for reducing chlorophyll residues to an acceptable level. During bleaching the oil is heated and passed through an adsorbent to remove chlorophyll and other colour-bearing compounds that impact the appearance and/or stability of the finished oil. The adsorbent used in the bleaching step is typically clay.
In the edible oil processing industry, the use of such steps typically reduces chlorophyll levels in processed oil to between 0.02 to 0.05 ppm. However the bleaching step increases processing cost and reduces oil yield due to entrainment in the bleaching clay. The use of clay may remove many desirable compounds such as carotenoids and tocopherol from the oil. Also the use of clay is expensive, this is particularly due to the treatment of the used clay (i.e. the waste) which can be difficult, dangerous (prone to self-ignition) and thus costly to handle. Thus attempts have been made to remove chlorophyll from oil by other means, for instance using the enzyme chlorophyllase.
In plants, chlorophyllase (chlase) is thought to be involved in chlorophyll degradation and catalyzes the hydrolysis of an ester bond in chlorophyll to yield chlorophyllide and phytol. WO 2006009676 describes an industrial process in which chlorophyll contamination can be reduced in a composition such as a plant oil by treatment with chlorophyllase. The water-soluble chlorophyllide which is produced in this process is also green in colour but can be removed by an aqueous extraction or silica treatment.
Chlorophyll is often partly degraded in the seeds used for oil production as well as during extraction of the oil from the seeds. One common modification is the loss of the magnesium ion from the porphyrin (chlorin) ring to form the derivative known as pheophytin (see
Pheophytin may be further degraded to pyropheophytin, both by the activity of plant enzymes during harvest and storage of oil seeds or by processing conditions (e.g. heat) during oil refining (see “Behaviour of Chlorophyll Derivatives in Canola Oil Processing”, JAOCS, Vol, no. 9 (September 1993) pages 837-841). One possible mechanism is the enzymatic hydrolysis of the methyl ester bond of the isocyclic ring of pheophytin followed by the non-enzymatic conversion of the unstable intermediate to pyropheophytin. A 28-29 kDa enzyme from Chenopodium album named pheophorbidase is reportedly capable of catalyzing an analogous reaction on pheophorbide, to produce the phytol-free derivative of pyropheophytin known as pyropheophorbide (see
Depending on the processing conditions, pyropheophytin can be more abundant than both pheophytin and chlorophyll in vegetable oils during processing (see Table 9 in volume 2.2. of Bailey's Industrial Oil and Fat Products (2005), 6th edition, Ed. by Fereidoon Shahidi, John Wiley & Sons). This is partly because of the loss of magnesium from chlorophyll during harvest and storage of the plant material. If an extended heat treatment at 90° C. or above is used, the amount of pyropheophytin in the oil is likely to increase and could be higher than the amount of pheophytin. Chlorophyll levels are also reduced by heating of oil seeds before pressing and extraction as well as the oil degumming and alkali treatment during the refining process. It has also been observed that phospholipids in the oil can complex with magnesium and thus reduce the amount of chlorophyll. Thus chlorophyll is a relatively minor contaminant compared to pyropheophytin (and pheophytin) in many plant oils.
There is a still a need for an improved process for removing chlorophyll and chlorophyll derivatives such as pheophytin and pyropheophytin from plant oils. In particular, there is a need for a process in which chlorophyll and chlorophyll derivatives are removed with enhanced efficiency, whilst reducing the loss of other desirable compounds from the oil.
In one aspect the present invention provides a process for refining a plant oil, comprising a step of contacting the oil with an enzyme which is capable of hydrolysing chlorophyll or a chlorophyll derivative, wherein the enzyme is contacted with the oil in the presence of at least 0.1% by weight phospholipid.
In some embodiments, the enzyme is contacted with the oil in the presence of less than 0.2% by weight lysophosholipid, for example less than 0.15%, less than 0.1% or less than 0.05% by weight, based on the total weight of oil.
In one embodiment, the enzyme is contacted with the oil before degumming of the oil. In another embodiment, the enzyme is contacted with the oil during a step of degumming of the oil. The degumming step may comprise, for example, water degumming, acid degumming, enzymatic degumming, and/or total degumming/neutralisation (e.g. addition of an acid to the oil followed by neutralisation with an alkali).
Where the enzyme is contacted with the oil before degumming, in particular embodiments an enzymatic degumming step may comprise contacting the oil with a phospholipase (e.g. phospholipase A1, phospholipase A2 or phospholipase C) or an acyltransferase. The acyltransferase may comprise, for example, the amino acid sequence of SEQ ID NO:23 or a sequence having at least 80% sequence identity thereto.
In another embodiment, the process comprises contacting the oil with the enzyme and a phospholipase which does not produce lysopholipids (e.g. phospholipase C) in a single step. For example, the enzyme may be contacted with the oil during an enzymatic degumming step using phospholipase C, i.e. the enzyme and phospholipase C are used simultaneously.
In further embodiments, the enzyme is contacted with the oil in the presence of at least 0.5%, at least 1%, at least 1.5% or at least 2% by weight phospholipid.
In further embodiments, the enzyme is contacted with the oil at a temperature of less than 80° C., preferably less than 70° C., preferably 55° C. to 65° C., preferably 58° to 62° C., e.g. about 60° C. Preferably the enzyme is contacted with the oil in the presence of 1 to 5% by weight water, e.g. about 1% or about 2% by weight water. In one embodiment, the enzyme is contacted with the oil at a pH of 6.0 to 6.8, e.g. 6.3 to 6.5.
Preferably the process does not comprise a step of clay treatment. The process preferably further comprises performing a deodorisation step to produce a deodorized oil and a distillate (e.g. an aqueous distillate or a nitrogenous distillate). Typically the process produces a level of carotenoids and/or tocopherol in the refined (deodorized or non-deodorized) oil and/or distillate which is elevated compared to a process comprising a clay treatment step.
In one embodiment the enzyme comprises a chlorophyllase, pheophytinase, pyropheophytinase or pheophytin pheophorbide hydrolase. For example, the enzyme may comprise a polypeptide sequence as defined in any one of SEQ ID NOs: 1, 2, 4, 6 or 8 to 15, or a functional fragment or variant thereof. Preferably the enzyme comprises a polypeptide sequence having at least 75% sequence identity to any one of SEQ ID NOs: 1, 2, 4, 6 or 8 to 15, e.g. over at least 50 amino acid residues. In particularly preferred embodiments, the enzyme comprises the sequence of SEQ ID NO:2 or SEQ ID NO:4 or a sequence having at least 90% sequence identity thereto.
In another aspect, the invention provides a refined plant oil obtainable by a process as defined above.
In a further aspect, the invention provides a distillate (e.g. an aqueous or nitrogenous distillate) obtainable by the process as defined above, i.e. a process as described herein comprising a deodorization step.
In a further aspect, the invention provides a process as defined above, to increase a level of carotenoids and/or tocopherol in a refined oil and/or a distillate obtained by deodorization of the oil.
As described herein, the activity of chlorophyllases and related enzymes in oil has been found to be dependent on the phospholipid content of the oil. Therefore in one embodiment the present invention provides an improved oil refining process in which chlorophyllase or a related enzyme is used in the presence of a minimum level of phospholipid. Moreover, based on the demonstration that elevated lysophospholipid levels are associated with reduced activity of chlorophyllases, in one embodiment the invention provides an improved process in which the enzyme is used in the presence of a low level of lysophospholipid. By enhancing the activity of the enzyme, the process of the present invention advantageously facilitates the removal of chlorophyll and chlorophyll derivatives typically without the need for a clay treatment step. This may increase the level of useful compounds such as tocopherol and carotenoids in the oil, which can be recovered in a deodorization step or retained in the finished product.
In one aspect the present invention relates to a process for refining a plant oil. Typically the process is used to remove chlorophyll and/or chlorophyll derivatives from the oil, or to reduce the level of chlorophyll and/or chlorophyll derivatives in the oil, for instance where the chlorophyll and/or chlorophyll derivatives are present as a contaminant.
Chlorophyll and Chlorophyll Derivatives
By “chlorophyll derivative” it is typically meant compounds which comprise both a porphyrin (chlorin) ring and a phytol group (tail), including magnesium-free phytol-containing derivatives such as pheophytin and pyropheophytin. Chlorophyll and (phytol-containing) chlorophyll derivatives are typically greenish is colour, as a result of the porphyrin (chlorin) ring present in the molecule. Loss of magnesium from the porphyrin ring means that pheophytin and pyropheophytin are more brownish in colour than chlorophyll. Thus the presence of chlorophyll and chlorophyll derivatives in an oil, can give such an oil an undesirable green, greenish or brownish colour. In one embodiment, the present process may be performed in order to remove or reduce the green or brown colouring present in the oil. Accordingly the present process may be referred to as a bleaching or de-colorizing process.
Enzymes used in the process may hydrolyse chlorophyll and phytol-containing chlorophyll derivatives to cleave the phytol tail from the chlorin ring. Hydrolysis of chlorophyll and chlorophyll derivatives typically results in compounds such as chlorophyllide, pheophorbide and pyropheophorbide which are phytol-free derivatives of chlorophyll. These compounds still contain the colour-bearing porphyrin ring, with chlorophyllide being green and pheophorbide and pyropheophorbide a reddish brown colour. In some embodiments, it may also be desirable to remove these phytol-free derivatives and to reduce the green/red/brown colouring in the oil. Thus in one embodiment of the invention, the process may further comprise a step of removing or reducing the level of phytol-free chlorophyll derivatives in the oil. The process may involve bleaching or de-colorizing to remove the green and/or red/brown colouring of the oil.
The chlorophyll or chlorophyll derivative may be either a or b forms. Thus as used herein, the term “chlorophyll” includes chlorophyll a and chlorophyll b. In a similar way both a and b forms are covered when referring to pheophytin, pyropheophytin, chlorophyllide, pheophorbide and pyropheophorbide.
Plant Oils
Any plant oil may be treated according to the present process, in order to remove undesirable contamination by chlorophyll and/or chlorophyll derivatives. The oil may be derived from any type of plant, and from any part of a plant, including whole plants, leaves, stems, flowers, roots, plant protoplasts, seeds and plant cells and progeny of same. The class of plants from which products can be treated in the method of the invention includes higher plants, including angiospeims (monocotyledonous and dicotyledonous plants), as well as gymnosperms. It includes plants of a variety of ploidy levels, including polyploid, diploid, haploid and hemizygous states.
In preferred embodiments, the oil may comprise a vegetable oil, including oils processed from oil seeds or oil fruits (e.g. seed oils such as canola (rapeseed) oil and fruit oils such as palm). Examples of suitable oils include rice bran, soy, canola (rape seed), palm, olive, cottonseed, corn, palm kernel, coconut, peanut, sesame or sunflower. The process of the invention can be used in conjunction with methods for processing essential oils, e.g., those from fruit seed oils, e.g. grapeseed, apricot, borage, etc. The process of the invention can be used in conjunction with methods for processing high phosphorus oils (e.g. a soy bean oil). Preferably the oil is a crude plant oil.
Chlorophyll and Chlorophyll Derivatives in Oil
The chlorophyll and/or chlorophyll derivatives (e.g. chlorophyll, pheophytin and/or pyropheophytin) may be present in the oil naturally, as a contaminant, or as an undesired component in a processed product. The chlorophyll and/or chlorophyll derivatives (e.g. chlorophyll, pheophytin and/or pyropheophytin) may be present at any level in the oil. Typically chlorophyll, pheophytin and/or pyropheophytin may be present as a natural contaminant in the oil at a concentration of 0.001 to 1000 mg/kg (0.001 to 1000 ppm, 10−7 to 10−1 wt %), based on the total weight of the oil. In further embodiments, the chlorophyll and/or chlorophyll derivatives may be present in the oil at a concentration of 0.1 to 100, 0.5 to 50, 1 to 50, 1 to 30 or 1 to 10 mg/kg, based on the total weight of the oil.
Phytol-free chlorophyll derivatives may also be present in the oil. For instance, chlorophyllide, pyropheophorbide and/or pyropheophorbide may be present at any level in the oil. Typically chlorophyllide, pyropheophorbide and/or pyropheophorbide may be present in the oil, either before or after treatment with an enzyme according to the method of the present invention, at a concentration of 0.001 to 1000 mg/kg (0.001 to 1000 ppm, 10−7 to 10−1 wt %), based on the total weight of the oil. In further embodiments, the chlorophyllide, pyropheophorbide and/or pyropheophorbide may be present in the composition at a concentration of 0.1 to 100, 0.5 to 50, 1 to 50, 1 to 30 or 1 to 10 mg/kg, based on the total weight of the composition.
Enzymes Hydrolysing Chlorophyll or a Chlorophyll Derivative
The process of the present invention comprises a step of contacting the oil with an enzyme which is capable of hydrolysing chlorophyll or a chlorophyll derivative. Typically “hydrolyzing chlorophyll or a chlorophyll derivative” means hydrolysing an ester bond in chlorophyll or a (phytol-containing) chlorophyll derivative, e.g. to cleave a phytol group from the chlorin ring in the chlorophyll or chlorophyll derivative. Thus the enzyme typically has an esterase or hydrolase activity. Preferably the enzyme has esterase or hydrolase activity in an oil phase, and optionally also in an aqueous phase.
Thus the enzyme may, for example, be a chlorophyllase, pheophytinase or pyropheophytinase. Preferably, the enzyme is capable of hydrolysing at least one, at least two or all three of chlorophyll, pheophytin and pyropheophytin. In a particularly preferred embodiment, the enzyme has chlorophyllase, pheophytinase and pyropheophytinase activity. In further embodiments, two or more enzymes may be used in the method, each enzyme having a different substrate specificity. For instance, the method may comprise the combined use of two or three enzymes selected from a chlorophyllase, a pheophytinase and a pyropheophytinase.
Any polypeptide having an activity that can hydrolyse chlorophyll or a chlorophyll derivative can be used as the enzyme in the process of the invention. By “enzyme” it is intended to encompass any polypeptide having hydrolytic activity on chlorophyll or a chlorophyll derivative, including e.g. enzyme fragments, etc. Any isolated, recombinant or synthetic or chimeric (or a combination of synthetic and recombinant) polypeptide can be used.
Enzyme (Chlorophyllase, Pheophytinase or Pyropheophytinase) Activity Assay
Hydrolytic activity on chlorophyll or a chlorophyll derivative may be detected using any suitable assay technique, for example based on an assay described herein. For example, hydrolytic activity may be detected using fluorescence-based techniques. In one suitable assay, a polypeptide to be tested for hydrolytic activity on chlorophyll or a chlorophyll derivative is incubated in the presence of a substrate, and product or substrate levels are monitored by fluorescence measurement. Suitable substrates include e.g. chlorophyll, pheophytin and/or pyropheophytin. Products which may be detected include chlorophyllide, pheophorbide, pyropheophorbide and/or phytol.
Assay methods for detecting hydrolysis of chlorophyll or a chlorophyll derivative are disclosed in, for example, Ali Khamessan et al. (1994), Journal of Chemical Technology & Biotechnology, 60(1), pages 73-81; Klein and Vishniac (1961), J. Biol. Chem. 236: 2544-2547; and Kiani et al. (2006), Analytical Biochemistry 353: 93-98.
Alternatively, a suitable assay may be based on HPLC detection and quantitation of substrate or product levels following addition of a putative enzyme, e.g. based on the techniques described below. In one embodiment, the assay may be performed as described in Hornero-Mendez et al. (2005), Food Research international 38(8-9): 1067-1072. In another embodiment, the following assay may be used:
170 μl mM HEPES, pH 7.0 is added 20 μl 0.3 mM chlorophyll, pheophytin or pyropheophytin dissolved in acetone. The enzyme is dissolved in 50 mM HEPES, pH 7.0. 10 μl enzyme solution is added to 190 μl substrate solution to initiate the reaction and incubated at 40° C. for various time periods. The reaction was stopped by addition of 350 μl acetone. Following centrifugation (2 min at 18,000 g) the supernatant was analyzed by HPLC, and the amounts of (i) chlorophyll and chlorophyllide (ii) pheophytin and pheophorbide or (iii) pyropheophytin and pyropheophorbide determined.
One unit of enzyme activity is defined as the amount of enzyme which hydrolyzes one micromole of substrate (e.g. chlorophyll, pheophytin or pyropheophytin) per minute at 40° C., e.g. in an assay method as described herein.
In preferred embodiments, the enzyme used in the present method has chlorophyllase, pheophytinase and/or pyropheophytinase activity of at least 1000 U/g, at least 5000 U/g, at least 10000 U/g, or at least 50000 U/g, based on the units of activity per gram of the purified enzyme, e.g. as determined by an assay method described herein.
Chlorophyllases
In one embodiment, the enzyme is capable of hydrolyzing at least chlorophyll. Any polypeptide that catalyses the hydrolysis of a chlorophyll ester bond to yield chlorophyllide and phytol can be used in the process. For example, a chlorophyllase, chlase or chlorophyll chlorophyllido-hydrolyase or polypeptide having a similar activity (e.g., chlorophyll-chlorophyllido hydrolase 1 or chlase 1, or, chlorophyll-chlorophyllido hydrolase 2 or chlase 2, see, e.g. NCBI P59677-1 and P59678, respectively) can be used in the process.
In one embodiment the enzyme is a chlorophyllase classified under the Enzyme Nomenclature classification (E.C. 3.1.1.14). Any isolated, recombinant or synthetic or chimeric (a combination of synthetic and recombinant) polypeptide (e.g., enzyme or catalytic antibody) can be used, see e.g. Marchler-Bauer (2003) Nucleic Acids Res. 31: 383-387. In one aspect, the chlorophyllase may be an enzyme as described in WO 0229022 or WO 2006009676. For example, the Arabidopsis thaliana chlorophyllase can be used as described, e.g. in NCBI entry NM—123753. Thus the chlorophyllase may be a polypeptide comprising the sequence of SEQ ID NO:1 (see
In another embodiment, the chlorophyllase is derived from wheat, e.g. from Triticum sp., especially from Triticum aestivum. For example, the chlorophyllase may be polypeptide comprising the sequence of SEQ ID NO:2 (see
In another embodiment, the chlorophyllase is derived from Chlamydomonas sp., especially from Chlamydomonas reinhardtii. For example, the chlorophyllase may be a polypeptide comprising the sequence of SEQ ID NO:4 (see
Pheophytin Pheophorbide Hydrolase
In one embodiment, the enzyme is capable of hydrolyzing pheophytin and pyropheophytin. For example, the enzyme may be pheophytinase or pheophytin pheophorbide hydrolase (PPH), e.g. an enzyme as described in Schelbert et al., The Plant Cell 21:767-785 (2009).
PPH and related enzymes are capable of hydrolyzing pyropheophytin in addition to pheophytin. However PPH is inactive on chlorophyll. As described in Schelbert et al., PPH orthologs are commonly present in eukaryotic photosynthesizing organisms. PPHs represent a defined sub-group of α/β hydrolases which are phylogenetically distinct from chlorophyllases, the two groups being distinguished in terms of sequence homology and substrates.
In specific embodiments of the invention, the enzyme may be any known PPH derived from any species or a functional variant or fragment thereof or may be derived from any known PPH enzyme. For example, in one embodiment, the enzyme is a PPH from Arabidopsis thaliana, e.g. a polypeptide comprising the amino acid sequence of SEQ ID NO:6 (see
In further embodiments, the enzyme may be a PPH derived from any one of the following species: Arabidopsis thaliana, Populus trichocarpa, Vitis vinifera, Oryza sativa, Zea mays, Nicotiana tabacum, Ostreococcus lucimarinus, Ostreococcus taurii, Physcomitrella patens, Phaeodaciylum tricornutum, Chlamydomonas reinhardtii, or Micromonas sp. RCC299. For example, the enzyme may be a polypeptide comprising an amino acid sequence, or encoded by a nucleotide sequence, defined in one of the following database entries shown in Table 1, or a functional fragment or variant thereof:
Arabidopsis thaliana
Populus trichocarpa
Vitis vinifera
Oryza sativa (japonica)
Zea mays
Nicotiana tabacum
Ostreococcus lucimarinus
Ostreococcus tauri
Physcomitrella patens
Phaeodactylum tricornutum
Chlamydomonas reinhardtii
Micromonas sp. RCC299
For example, the enzyme may be a polypeptide as defined in any of SEQ ID NO:s 8 to 15 (
Variants and Fragments
Functional variants and fragments of known sequences which hydrolyse chlorophyll or a chlorophyll derivative may also be employed in the present invention. By “functional” it is meant that the fragment or variant retains a detectable hydrolytic activity on chlorophyll or a chlorophyll derivative. Typically such variants and fragments show homology to a known chlorophyllase, pheophytinase or pyropheophytinase sequence, e.g. at least about 50%, 60%, 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98%, 99%, or more sequence identity to a known chlorophyllase, pheophytinase or pyropheophytinase amino acid sequence, e.g. to SEQ ID NO:1 or any one of SEQ ID NOs: 1, 2, 4, 6 or 8 to 15, e.g. over a region of at least about 10, 20, 30, 50, 100, 200, 300, 500, or 1000 or more residues, or over the entire length of the sequence.
The percentage of sequence identity may be determined by analysis with a sequence comparison algorithm or by a visual inspection. In one aspect, the sequence comparison algorithm is a BLAST algorithm, e.g., a BLAST version 2.2.2 algorithm.
Other enzymes having chlorophyllase, pheophytinase and/or pyropheophytinase activity suitable for use in the process may be identified by determining the presence of conserved sequence motifs present e.g. in known chlorophyllase, pheophytinase or pyropheophytinase sequences. For example, conserved sequence motifs found in PPH enzymes include the following: LPGFGVG (SEQ ID NO:16), DFLGQG (SEQ ID NO:17), GNSLGG (SEQ ID NO:18), LVKGVTLLNATPFW (SEQ ID NO:19), HPAA (SEQ ID NO:20), EDPW (SEQ ID NO:21), and SPAGHCPH (SEQ ID NO:22). In some embodiments, an enzyme for use in the present invention may comprise one or more of these sequences. The GNSLGG (SEQ ID NO:18) motif contains an active site serine residue. Polypeptide sequences having suitable activity may be identified by searching genome databases, e.g. the microbiome metagenome database (JGI-DOE, USA), for the presence of these motifs.
Isolation and Production of Enzymes
Enzymes for use in the present invention may be isolated from their natural sources or may be, for example, produced using recombinant DNA techniques. Nucleotide sequences encoding polypeptides having chlorophyllase, pheophytinase and/or pyropheophytinase activity may be isolated or constructed and used to produce the corresponding polypeptides.
For example, a genomic DNA and/or cDNA library may be constructed using chromosomal DNA or messenger RNA from the organism producing the polypeptide. If the amino acid sequence of the polypeptide is known, labeled oligonucleotide probes may be synthesised and used to identify polypeptide-encoding clones from the genomic library prepared from the organism. Alternatively, a labelled oligonucleotide probe containing sequences homologous to another known polypeptide gene could be used to identify polypeptide-encoding clones. In the latter case, hybridisation and washing conditions of lower stringency are used.
Alternatively, polypeptide-encoding clones could be identified by inserting fragments of genomic DNA into an expression vector, such as a plasmid, transfoiming enzyme-negative bacteria with the resulting genomic DNA library, and then plating the transformed bacteria onto agar containing an enzyme inhibited by the polypeptide, thereby allowing clones expressing the poly-peptide to be identified.
In a yet further alternative, the nucleotide sequence encoding the polypeptide may be prepared synthetically by established standard methods, e.g. the phosphoroamidite method described by Beucage S. L. et al (1981) Tetrahedron Letters 22, p 1859-1869, or the method described by Matthes et al (1984) EMBO J. 3, p 801-805. In the phosphoroamidite method, oligonucleotides are synthesised, e.g. in an automatic DNA synthesiser, purified, annealed, ligated and cloned in appropriate vectors.
The nucleotide sequence may be of mixed genomic and synthetic origin, mixed synthetic and cDNA origin, or mixed genomic and cDNA origin, prepared by ligating fragments of synthetic, genomic or cDNA origin (as appropriate) in accordance with standard techniques. Each ligated fragment corresponds to various parts of the entire nucleotide sequence. The DNA sequence may also be prepared by polymerase chain reaction (PCR) using specific primers, for instance as described in U.S. Pat. No. 4,683,202 or in Saiki R K et at (Science (1988) 239, pp 487-491).
The term “nucleotide sequence” as used herein refers to an oligonucleotide sequence or polynucleotide sequence, and variant, homologues, fragments and derivatives thereof (such as portions thereof). The nucleotide sequence may be of genomic or synthetic or recombinant origin, which may be double-stranded or single-stranded whether representing the sense or antisense strand.
Typically, the nucleotide sequence encoding a polypeptide having chlorophyllase, pheophytinase and/or pyropheophytinase activity is prepared using recombinant DNA techniques. However, in an alternative embodiment of the invention, the nucleotide sequence could be synthesised, in whole or in part, using chemical methods well known in the art (see Caruthers M H et al (1980) Nuc Acids Res Symp Ser 215-23 and Horn T et at (1980) Nuc Acids Res Symp Ser 225-232).
Modification of Enzyme Sequences
Once an enzyme-encoding nucleotide sequence has been isolated, or a putative enzyme-encoding nucleotide sequence has been identified, it may be desirable to modify the selected nucleotide sequence, for example it may be desirable to mutate the sequence in order to prepare an enzyme in accordance with the present invention.
Mutations may be introduced using synthetic oligonucleotides. These oligonucleotides contain nucleotide sequences flanking the desired mutation sites. A suitable method is disclosed in Morinaga et al (Biotechnology (1984) 2, p646-649). Another method of introducing mutations into enzyme-encoding nucleotide sequences is described in Nelson and Long (Analytical Biochemistry (1989), 180, p 147-151).
Instead of site directed mutagenesis, such as described above, one can introduce mutations randomly for instance using a commercial kit such as the GeneMorph PCR mutagenesis kit from Stratagene, or the Diversify PCR random mutagenesis kit from Clontech. EP 0 583 265 refers to methods of optimising PCR based mutagenesis, which can also be combined with the use of mutagenic DNA analogues such as those described in EP 0 866 796. Error prone PCR technologies are suitable for the production of variants of enzymes which hydrolyse chlorophyll and/or chlorophyll derivatives with preferred characteristics. WO0206457 refers to molecular evolution of lipases.
A third method to obtain novel sequences is to fragment non-identical nucleotide sequences, either by using any number of restriction enzymes or an enzyme such as Dnase I, and reassembling full nucleotide sequences coding for functional proteins. Alternatively one can use one or multiple non-identical nucleotide sequences and introduce mutations during the reassembly of the full nucleotide sequence. DNA shuffling and family shuffling technologies are suitable for the production of variants of enzymes with preferred characteristics. Suitable methods for performing ‘shuffling’ can be found in EP0752008, EP1138763, EP1103606. Shuffling can also be combined with other forms of DNA mutagenesis as described in U.S. Pat. No. 6,180,406 and WO 01/34835.
Thus, it is possible to produce numerous site directed or random mutations into a nucleotide sequence, either in vivo or in vitro, and to subsequently screen for improved functionality of the encoded polypeptide by various means. Using in silico and exo mediated recombination methods (see WO 00/58517, U.S. Pat. No. 6,344,328, U.S. Pat. No. 6,361,974), for example, molecular evolution can be performed where the variant produced retains very low homology to known enzymes or proteins. Such variants thereby obtained may have significant structural analogy to known chlorophyllase, pheophytinase or pyropheophytinase enzymes, but have very low amino acid sequence homology.
As a non-limiting example, in addition, mutations or natural variants of a polynucleotide sequence can be recombined with either the wild type or other mutations or natural variants to produce new variants. Such new variants can also be screened for improved functionality of the encoded polypeptide.
The application of the above-mentioned and similar molecular evolution methods allows the identification and selection of variants of the enzymes of the present invention which have preferred characteristics without any prior knowledge of protein structure or function, and allows the production of non-predictable but beneficial mutations or variants. There are numerous examples of the application of molecular evolution in the art for the optimisation or alteration of enzyme activity, such examples include, but are not limited to one or more of the following: optimised expression and/or activity in a host cell or in vitro, increased enzymatic activity, altered substrate and/or product specificity, increased or decreased enzymatic or structural stability, altered enzymatic activity/specificity in preferred environmental conditions, e.g. temperature, pH, substrate.
As will be apparent to a person skilled in the art, using molecular evolution tools an enzyme may be altered to improve the functionality of the enzyme. Suitably, a nucleotide sequence encoding an enzyme (e.g. a chlorophyllase, pheophytinase and/or pyropheophytinase) used in the invention may encode a variant enzyme, i.e. the variant enzyme may contain at least one amino acid substitution, deletion or addition, when compared to a parental enzyme. Variant enzymes retain at least 1%, 2%, 3%, 5%, 10%, 15%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 95%, 97%, or 99% identity with the parent enzyme. Suitable parent enzymes may include any enzyme with hydrolytic activity on chlorophyll and/or a chlorophyll derivative.
Polypeptide Sequences
The present invention also encompasses the use of amino acid sequences encoded by a nucleotide sequence which encodes a pyropheophytinase for use in any one of the methods and/or uses of the present invention.
As used herein, the term “amino acid sequence” is synonymous with the term “polypeptide” and/or the term “protein”. in some instances, the term “amino acid sequence” is synonymous with the term “peptide”. The amino acid sequence may be prepared/isolated from a suitable source, or it may be made synthetically or it may be prepared by use of recombinant DNA techniques. Suitably, the amino acid sequences may be obtained from the isolated polypeptides taught herein by standard techniques.
One suitable method for determining amino acid sequences from isolated polypeptides is as follows. Purified polypeptide may be freeze-dried and 100 μg of the freeze-dried material may be dissolved in 50 μl of a mixture of 8 M urea and 0.4 M ammonium hydrogen carbonate, pH 8.4. The dissolved protein may be denatured and reduced for 15 minutes at 50° C. following overlay with nitrogen and addition of 5 μl of 45 mM dithiothreitol. After cooling to room temperature, 5 μl of 100 mM iodoacetamide may be added for the cysteine residues to be derivatized for 15 minutes at room temperature in the dark under nitrogen.
135 μl of water and 5 μg of endoproteinase Lys-C in 5 μl of water may be added to the above reaction mixture and the digestion may be carried out at 37° C. under nitrogen for 24 hours. The resulting peptides may be separated by reverse phase HPLC on a VYDAC C18 column (0.46×15cm; 10 μm; The Separation Group, California, USA) using solvent A: 0.1% TFA in water and solvent B: 0.1% TFA in acetonitrile. Selected peptides may be re-chromatographed on a Develosil C18 column using the same solvent system, prior to N-terminal sequencing. Sequencing may be done using an Applied Biosystems 476A sequencer using pulsed liquid fast cycles according to the manufacturer's instructions (Applied Biosystems, California, USA).
Sequence Comparison
Here, the term “homologue” means an entity having a certain homology with the subject amino acid sequences and the subject nucleotide sequences. Here, the term “homology” can be equated with “identity”. The homologous amino acid sequence and/or nucleotide sequence should provide and/or encode a polypeptide which retains the functional activity and/or enhances the activity of the enzyme.
In the present context, a homologous sequence is taken to include an amino acid sequence which may be at least 75, 85 or 90% identical, preferably at least 95 or 98% identical to the subject sequence. Typically, the homologues will comprise the same active sites etc. as the subject amino acid sequence. Although homology can also be considered in terms of similarity (i.e. amino acid residues having similar chemical properties/functions), in the context of the present invention it is preferred to express homology in terms of sequence identity.
In the present context, a homologous sequence is taken to include a nucleotide sequence which may be at least 75, 85 or 90% identical, preferably at least 95 or 98% identical to a nucleotide sequence encoding a polypeptide of the present invention (the subject sequence). Typically, the homologues will comprise the same sequences that code for the active sites etc. as the subject sequence. Although homology can also be considered in terms of similarity (i.e. amino acid residues having similar chemical properties/functions), in the context of the present invention it is preferred to express homology in terms of sequence identity.
Homology comparisons can be conducted by eye, or more usually, with the aid of readily available sequence comparison programs. These commercially available computer programs can calculate % homology between two or more sequences. % homology may be calculated over contiguous sequences, i.e. one sequence is aligned with the other sequence and each amino acid in one sequence is directly compared with the corresponding amino acid in the other sequence, one residue at a time. This is called an “ungapped” alignment. Typically, such ungapped alignments are performed only over a relatively short number of residues.
Although this is a very simple and consistent method, it fails to take into consideration that, for example, in an otherwise identical pair of sequences, one insertion or deletion will cause the following amino acid residues to be put out of alignment, thus potentially resulting in a large reduction in % homology when a global alignment is performed. Consequently, most sequence comparison methods are designed to produce optimal alignments that take into consideration possible insertions and deletions without penalising unduly the overall homology score. This is achieved by inserting “gaps” in the sequence alignment to try to maximise local homology.
However, these more complex methods assign “gap penalties” to each gap that occurs in the alignment so that, for the same number of identical amino acids, a sequence alignment with as few gaps as possible—reflecting higher relatedness between the two compared sequences—will achieve a higher score than one with many gaps. “Affine gap costs” are typically used that charge a relatively high cost for the existence of a gap and a smaller penalty for each subsequent residue in the gap. This is the most commonly used gap scoring system. High gap penalties will of course produce optimised alignments with fewer gaps. Most alignment programs allow the gap penalties to be modified. However, it is preferred to use the default values when using such software for sequence comparisons.
Calculation of maximum % homology therefore firstly requires the production of an optimal alignment, taking into consideration gap penalties. A suitable computer program for carrying out such an alignment is the Vector NTI Advance™ 11 (Invitrogen Corp.). Examples of other software that can perform sequence comparisons include, but are not limited to, the BLAST package (see Ausubel et al 1999 Short Protocols in Molecular Biology, 4th Ed—Chapter 18), and FASTA (Altschul et al 1990 J. Mol. Biol. 403-410). Both BLAST and FASTA are available for offline and online searching (see Ausubel et al 1999, pages 7-58 to 7-60). However, for some applications, it is preferred to use the Vector NTI Advance™ 11 program. A new tool, called BLAST 2 Sequences is also available for comparing protein and nucleotide sequence (see FEMS Microbiol Lett 1999 174(2): 247-50; and FEMS Microbiol Lett 1999 177(1): 187-8.).
Although the final % homology can be measured in terms of identity, the alignment process itself is typically not based on an all-or-nothing pair comparison. Instead, a scaled similarity score matrix is generally used that assigns scores to each pairwise comparison based on chemical similarity or evolutionary distance. An example of such a matrix commonly used is the BLOSUM62 matrix—the default matrix for the BLAST suite of programs. Vector NTI programs generally use either the public default values or a custom symbol comparison table if supplied (see user manual for further details). For some applications, it is preferred to use the default values for the Vector NTI Advance™ 11 package.
Alternatively, percentage homologies may be calculated using the multiple alignment feature in Vector NTI Advance™ 11 (Invitrogen Corp.), based on an algorithm, analogous to CLUSTAL (Higgins D G & Sharp P M (1988), Gene 73(1), 237-244). Once the software has produced an optimal alignment, it is possible to calculate % homology, preferably % sequence identity. The software typically does this as part of the sequence comparison and generates a numerical result.
Should Gap Penalties be used when determining sequence identity, then preferably the default parameters for the programme are used for pairwise alignment. For example, the following parameters are the current default parameters for pairwise alignment fnr BLAST 2:
In one embodiment, preferably the sequence identity for the nucleotide sequences and/or amino acid sequences may be determined using BLAST2 (blastn) with the scoring parameters set as defined above.
For the purposes of the present invention, the degree of identity is based on the number of sequence elements which are the same. The degree of identity in accordance with the present invention for amino acid sequences may be suitably determined by means of computer programs known in the art such as Vector NTI Advance™ 11 (Invitrogen Corp.). For pairwise alignment the scoring parameters used are preferably BLOSUM62 with Gap existence penalty of lland Gap extension penalty of 1.
Suitably, the degree of identity with regard to a nucleotide sequence is determined over at least 20 contiguous nucleotides, preferably over at least 30 contiguous nucleotides, preferably over at least 40 contiguous nucleotides, preferably over at least 50 contiguous nucleotides, preferably over at least 60 contiguous nucleotides, preferably over at least 100 contiguous nucleotides. Suitably, the degree of identity with regard to a nucleotide sequence may be determined over the whole sequence.
Amino Acid Mutations
The sequences may also have deletions, insertions or substitutions of amino acid residues which produce a silent change and result in a functionally equivalent substance. Deliberate amino acid substitutions may be made on the basis of similarity in polarity, charge, solubility, hydrophobicity, hydrophilicity, and/or the amphipathic nature of the residues as long as the secondary binding activity of the substance is retained. For example, negatively charged amino acids include aspartic acid and glutamic acid; positively charged amino acids include lysine and arginine; and amino acids with uncharged polar head groups having similar hydrophilicity values include leucine, isoleucine, valine, glycine, alanine, asparagine, glutamine, serine, threonine, phenylalanine, and tyrosine.
Conservative substitutions may be made, for example according to the Table below. Amino acids in the same block in the second column and preferably in the same line in the third column may be substituted for each other:
The present invention also encompasses homologous substitution (substitution and replacement are both used herein to mean the interchange of an existing amino acid residue, with an alternative residue) that may occur i.e. like-for-like substitution such as basic for basic, acidic for acidic, polar for polar etc. Non-homologous substitution may also occur i.e. from one class of residue to another or alternatively involving the inclusion of unnatural amino acids such as ornithine (hereinafter referred to as Z), diaminobutyric acid ornithine (hereinafter referred to as B), norleucine ornithine (hereinafter referred to as O), pyriylaianine, thienylalanine, naphthylalanine and phenylglycine. Replacements may also be made by unnatural amino acids.
Variant amino acid sequences may include suitable spacer groups that may be inserted between any two amino acid residues of the sequence including alkyl groups such as methyl, ethyl or propyl groups in addition to amino acid spacers such as glycine or β-alanine residues. A further form of variation, involves the presence of one or more amino acid residues in peptoid form, will be well understood by those skilled in the art. For the avoidance of doubt, “the peptoid faun” is used to refer to variant amino acid residues wherein the α-carbon substituent group is on the residue's nitrogen atom rather than the α-carbon. Processes for preparing peptides in the peptoid form are known in the art, for example Simon R J et al., PNAS (1992) 89(20), 9367-9371 and Horwell D C, Trends Biotechnol. (1995) 13(4), 132-134.
Nucleotide Sequences
Nucleotide sequences for use in the present invention or encoding a polypeptide having the specific properties defined herein may include within them synthetic or modified nucleotides. A number of different types of modification to oligonucleotides are known in the art. These include methylphosphonate and phosphorothioate backbones and/or the addition of acridine or polylysine chains at the 3′ and/or 5′ ends of the molecule. For the purposes of the present invention, it is to be understood that the nucleotide sequences described herein may be modified by any method available in the art. Such modifications may be carried out in order to enhance the in vivo activity or life span of nucleotide sequences.
The present invention also encompasses the use of nucleotide sequences that are complementary to the sequences discussed herein, or any derivative, fragment or derivative thereof If the sequence is complementary to a fragment thereof then that sequence can be used as a probe to identify similar coding sequences in other organisms etc.
Polynucleotides which are not 100% homologous to the sequences of the present invention but fall within the scope of the invention can be obtained in a number of ways. Other variants of the sequences described herein may be obtained for example by probing DNA libraries made from a range of individuals, for example individuals from different populations. In addition, other viral/bacterial, or cellular homologues particularly cellular homologues found in plant cells, may be obtained and such homologues and fragments thereof in general will be capable of selectively hybridising to the sequences shown in the sequence listing herein. Such sequences may be obtained by probing cDNA libraries made from or genomic DNA libraries from other plant species, and probing such libraries with probes comprising all or part of any one of the sequences in the attached sequence listings under conditions of medium to high stringency. Similar considerations apply to obtaining species homologues and allelic variants of the polypeptide or nucleotide sequences of the invention.
Variants and strain/species homologues may also be obtained using degenerate PCR which will use primers designed to target sequences within the variants and homologues encoding conserved amino acid sequences within the sequences of the present invention. Conserved sequences can be predicted, for example, by aligning the amino acid sequences from several variants/homologues. Sequence alignments can be performed using computer software known in the art. For example the GCG Wisconsin PileUp program is widely used.
The primers used in degenerate PCR will contain one or more degenerate positions and will be used at stringency conditions lower than those used for cloning sequences with single sequence primers against known sequences.
Alternatively, such polynucleotides may be obtained by site directed mutagenesis of characterised sequences. This may be useful where for example silent codon sequence changes are required to optimise codon preferences for a particular host cell in which the polynucleotide sequences are being expressed. Other sequence changes may be desired in order to introduce restriction polypeptide recognition sites, or to alter the property or function of the polypeptides encoded by the polynucleotides.
Polynucleotides (nucleotide sequences) of the invention may be used to produce a primer, e.g. a PCR primer, a primer for an alternative amplification reaction, a probe e.g. labelled with a revealing label by conventional means using radioactive or non-radioactive labels, or the polynucleotides may be cloned into vectors. Such primers, probes and other fragments will be at least 15, preferably at least 20, for example at least 25, 30 or 40 nucleotides in length, and are also encompassed by the term polynucleotides of the invention as used herein.
Polynucleotides such as DNA polynucleotides and probes according to the invention may be produced recombinantly, synthetically, or by any means available to those of skill in the art. They may also be cloned by standard techniques.
In general, primers will be produced by synthetic means, involving a stepwise manufacture of the desired nucleic acid sequence one nucleotide at a time. Techniques for accomplishing this using automated techniques are readily available in the art.
Longer polynucleotides will generally be produced using recombinant means, for example using a PCR (polymerase chain reaction) cloning techniques. This will involve making a pair of primers (e.g. of about 15 to 30 nucleotides) flanking a region of the pyropheophytinase sequence which it is desired to clone, bringing the primers into contact with mRNA or cDNA obtained from a plant cell, performing a polymerase chain reaction under conditions which bring about amplification of the desired region, isolating the amplified fragment (e.g. by purifying the reaction mixture on an agarose gel) and recovering the amplified DNA. The primers may be designed to contain suitable restriction enzyme recognition sites so that the amplified DNA can be cloned into a suitable cloning vector.
Enzyme Formulation and Dosage
Enzymes used in the methods of the invention can be formulated or modified, e.g., chemically modified, to enhance oil solubility, stability, activity or for immobilization. For example, enzymes used in the methods of the invention can be formulated to be amphipathic or more lipophilic. For example, enzymes used in the methods of the invention can be encapsulated, e.g., in liposomes or gels, e.g., alginate hydrogels or alginate beads or equivalents. Enzymes used in the methods of the invention can be formulated in micellar systems, e.g., a ternary micellar (TMS) or reverse micellar system (RMS) medium Enzymes used in the methods of the invention can be formulated as described in Yi (2002) J. of Molecular Catalysis B: Enzymatic, Vol. 19, pgs 319-325.
The enzymatic reactions of the methods of the invention, e.g. the step of contacting the oil with an enzyme which hydrolyses chlorophyll or a chlorophyll derivative, can be done in one reaction vessel or multiple vessels. In one aspect, the enzymatic reactions of the methods of the invention are done in a vegetable oil refining unit or plant.
The method of the invention can be practiced with immobilized enzymes, e.g. an immobilized chlorophyllase, pheophytinase and/or pyropheophytinase. The enzyme can be immobilized on any organic or inorganic support. Exemplary inorganic supports include alumina, celite, Dowex-1-chloride, glass beads and silica gel. Exemplary organic supports include DEAE-cellulose, alginate hydrogels or alginate beads or equivalents. In various aspects of the invention, immobilization of the enzyme can be optimized by physical adsorption on to the inorganic support. Enzymes used to practice the invention can be immobilized in different media, including water, Tris-HCl buffer solution and a ternary micellar system containing Tris-HCl buffer solution, hexane and surfactant. The enzyme can be immobilized to any type of substrate, e.g. filters, fibers, columns, beads, colloids, gels, hydrogels, meshes and the like.
The enzyme may be dosed into the oil in any suitable amount. For example, the enzyme may be dosed in a range of about 0.001 to 10 U/g of the composition, preferably 0.01 to 1 U/g, e.g. 0.01 to 0.1 U/g of the oil. One unit is defined as the amount of enzyme which hydrolyses 1 μmol of substrate (e.g. chlorophyll, pheophytin and/or pyropheophytin) per minute at 40° C., e.g. under assay conditions as described in J. Biol. Chem. (1961) 236: 2544-2547.
Phospholipid Content
In the process of the present invention, the enzyme is contacted with the oil in the presence of at least 0.1% by weight phospholipid. For example, the phospholipid content of the oil may be at least 0.1% by weight, e.g. based on the total weight of the oil composition, for at least a part of a time during which the enzyme is incubated with the oil (e.g. at least at a time when the enzyme is added to the oil).
In some embodiments, for example where the enzyme is added during a degumming step, the phospholipid content of the oil may decrease during the time in which the enzyme is incubated with the oil. However, provided that the phospholipid content of the oil is 0.1% by weight or above for at least part of the incubation with the enzyme (e.g. at the start of the incubation), the enzyme is likely to be active. Therefore in some embodiments the phospholipid content of the oil may be less than 0.1% by weight during a part of the incubation period with the enzyme.
The phospholipid is typically present as a natural component of a crude plant oil, although in some embodiments phospholipid may be added to the oil to be treated with the enzyme. Phospholipids commonly found in crude plant oils include phosphatidyl choline (PC), phosphatidyl inositol (PI), phosphatidyl ethanolamine (PE), phosphatidyl serine (PS) and phosphatidic acid (PA). In preferred embodiments, the phospholipid comprises one or more of PC, PI, PE, PS and PA. Phospholipids are typically present in crude oils in the form of lecithin, the major component of which is PC. Thus in one embodiment, the phospholipid comprises lecithin. The term lecithin as used herein encompasses phosphatidyl choline, phosphatidyl inositol, phosphatidyl ethanolamine, phosphatidyl serine and phosphatidic acid.
The phospholipid (e.g. PC, PI, PE, PS, PA and/or lecithin) content of the oil is at least 0.1% by weight during contact with the enzyme. In particular embodiments, the phospholipid content is at least 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2.0%, 2.1%, 2.2%, 2.3%, 2.4%, 2.5%, 2.6%, 2.7%, 2.8%, 2.9% or at least 3.0% by weight, e.g. based on the total weight of the oil. Preferably the phospholipid content is up to 5.0%, up to 4.0%, or up to 3.0% by weight. For example, the phospholipid content of the oil may be 0.1 to 5.0%, 0.1 to 4.0%, 0.1 to 3.0%, 0.3 to 5.0%, 0.3 to 4.0%, 0.3 to 3.0%, 0.5 to 5.0%, 0.5 to 4.0%, 0.5 to 3.0%, 1.0 to 5.0%, 1.0 to 4.0%, 1.0 to 3.0%, 2.0 to 5.0%, 2.0 to 4.0% or 2.0 to 3.0% by weight, e.g. based on the total weight of the oil.
The phospholipid content of plant oils varies according to the particular source and nature of the oil and the stage of the refining process. The phospholipid content of crude plant oils may be up to 5% by weight at the start of the process, but following a water degumming step the phospholipid content typically falls to 1% by weight or below, e.g. around 0.3% by weight. Following an enzymatic degumming step (e.g. using a phospholipase) or a total degumming step (e.g. comprising an acid treatment/caustic neutralization) the phospholipid content may fall much lower, for example below 0.1% or even below 0.01% by weight based on the total weight of the oil. Typical phospholipid contents in % by weight of some common oils are shown below:
The values in the table above are taken from Bailey's industrial Oil and Fat Products (2005), 6th edition, Ed. by Fereidoon Shahidi, John Wiley & Sons, and the phospholipid content of other oils is also described therein or is well-known in the art. The phospholipid content of oils may be determined using standard methods. For example, phospholipid levels in oils may be determined as described in J. Amer. Oil. Chem. Soc. 58, 561 (1981). In one embodiment phospholipid levels may be determined by thin-layer chromatography (TLC) analysis, e.g. as described in WO 2006/008508 or WO 03/100044. Phospholipid levels in oil can also be determined by (a) AOCS Recommended Practice Ca 19-86 (reapproved 2009), “Phospholipids in Vegetable Oils Nephelometric Method” or (b) AOCS Official Method Ca 20-99 (reapproved 2009), “Analysis for Phosphorus in Oil by Inductively Coupled Plasma Optical Emission Spectroscopy”.
Thus in one preferred embodiment, the enzyme is contacted with a crude plant oil (e.g. an oil comprising at least 0.5%, at least 1.0% or at least 2% by weight phospholipid). In another embodiment, the enzyme is contacted with a water degummed plant oil (e.g. an oil comprising 0.1 to 1% by weight phospholipid).
Lysophospholipid Content
In a preferred embodiment of the process, the enzyme is contacted with the oil at a time when a concentration of lysophospholipid in the oil is as low as possible. For instance, the enzyme may be contacted with the oil in the presence of less than 0.2% by weight lysophosholipid. By “in the presence of less than 0.2% by weight lysophosholipid” it is meant that the lysophospholipid content in the oil is less than 0.2% by weight, e.g. based on the total weight of the oil composition, for at least a part of a time during which the enzyme is incubated with the oil (e.g. at least at a time when the enzyme is added to the oil). The lysophospholipid content in the oil may be any value below 0.2% by weight, including zero.
In some embodiments, for example where the enzyme is added during a degumming step, the lysophospholipid content of the oil may increase during the time in which the enzyme is incubated with the oil. This is particularly the case where the process comprises an enzymatic degumming step using an enzyme which generates lysophospholipids. Lysophospholipids are typically produced during oil processing by cleavage of an acyl (fatty acid) chain from phospholipids, leaving a single acyl chain, a phosphate group, optionally a headgroup and a free alcohol attached to the glyceryl moiety. Enzymes used in degumming such as phospholipases (in particular phospholipase A1 and A2) and acyltransferases may generate lysophospholipids in the oil. In embodiments where the process comprises an enzymatic degumming step using an enzyme which generates lysophospholipids, the enzyme which hydrolyses chlorophyll or a chlorophyll derivative is preferably contacted with the oil before the enzymatic degumming step.
In one embodiment, a lysophospholipase may be used in combination with a phospholipase or acyltransferase in the degumming step. Lysophospholipases (EC 3.1.1.5) are enzymes that can hydrolyze lysophospholipids to release fatty acid. Use of a lysophospholipase may help to reduce the production of lysophospholipids in the oil during the degumming step, e.g. to maintain the lysophospholipid content of the oil below about 0.2% by weight. Suitable lysophospholipases are disclosed, for example, in Masuda et al., Eur. J. Biochem., 202,783-787 (1991); WO 98/31790; WO 01/27251 and WO 2008/040465.
Phospholipase C is another enzyme which may be used in degumming. Phospholipase C cleaves phospholipids between the glyceryl and phosphate moieties, leaving diacylglycerol and a phosphate group (attached to a headgroup if present). Thus in contrast to phospholipase A1 and A2, phospholipase C does not produce lysophospholipids. In embodiments where the process comprises an enzymatic degumming step using an enzyme which does not produce lysophospholipids (e.g. phospholipase C), the enzyme which hydrolyses chlorophyll or a chlorophyll derivative may be contacted with the oil either before or during the enzymatic degumming step.
In particular embodiments, the lysophospholipid content of the oil is less than 0.2%, less than 0.15%, less than 0.1% or less than 0.05% by weight, based on the total weight of oil. In general, concentrations of lysophospholipid which are as low as possible are desirable.
Lysophospholipids which may be present in the oil include lysophosphatidylcholine (LPC), lysophosphatidylinositol (LPI), lysophosphatidylethanolamine (LPE), lysophosphatidylserine (LPS) and lysophosphatidic acid (LPA). It is particularly preferred that the level of LPC and LPE in the oil is as low as possible. In preferred embodiments, the concentration of LPC and/or LPE is less than 0.2%, less than 0.15%, less than 0.1% or less than 0.05% by weight, based on the total weight of oil.
The lysophospholipid content of oils may be determined using standard methods, e.g. as described above for phospholipids, including using HPLC or TLC analysis methods. Suitable methods are described in AOCS Recommended Practice Ja 7-86 (reapproved 2009), “Phospholipids in Lecithin Concentrates by Thin-Layer Chromatography” or Journal of Chromatography A, 864 (1999) 179-182.
Enzyme Reaction Conditions
In general the oil may be incubated (or admixed) with the enzyme between about 5° C. to and about 100° C., more preferably between 10° C. to about 90° C., more preferably between about 15° C. to about 80° C., more preferably between about 20° C. to about 75° C.
At higher temperatures pheophytin is decomposed to pyropheophytin, which is generally less preferred because some chlorophyllases are less active on pyropheophytin compared to pheophytin. In addition, the chlorophyllase degradation product of pyropheophytin, pyropheophorbide, is less water soluble compared to pheophorbide and thus more difficult to remove from the oil afterwards. The enzymatic reaction rate is increased at higher temperatures but it is favourable to keep the conversion of pheophytin to pyropheophytin to a minimum.
In view of the above, in particularly preferred embodiments the oil is incubated with the enzyme at below about 80° C., preferably below about 70° C., preferably at about 68° C. or below, preferably at about 65° C. or below, in order to reduce the amount of conversion to pyropheophytin. However, in order to keep a good reaction rate it is preferred to keep the temperature of the oil above 50° C. during incubation with the enzyme. Accordingly preferred temperature ranges for the incubation of the enzyme with the oil include about 50° C. to below about 70° C., about 50° C. to about 65° C. and about 55° C. to about 65° C. Preferably the enzyme is contacted with the oil at about 57° C. to about 63° C., preferably about 58° C. to about 62° C., e.g about 60° C.
Preferably the temperature of the oil may be at the desired reaction temperature when the enzyme is admixed therewith. The oil may be heated and/or cooled to the desired temperature before and/or during enzyme addition. Therefore in one embodiment it is envisaged that a further step of the process according to the present invention may be the cooling and/or heating of the oil.
Suitably the reaction time (i.e. the time period in which the enzyme is incubated with the oil), preferably with agitation, is for a sufficient period of time to allow hydrolysis of chlorophyll and chlorophyll derivatives, e.g. to form phytol and chlorophyllide, pheophorbide and/or pyropheophorbide. For example, the reaction time may be at least about 1 minute, more preferable at least about 5 minutes, more preferably at least about 10 minutes. In some embodiments the reaction time may be between about 15 minutes to about 6 hours, preferably between about 15 minutes to about 60 minutes, preferably about 30 to about 120 minutes. In some embodiments, the reaction time may up to 6 hours.
Preferably the process is can ied out between about pH 4.0 and about pH 10.0, more preferably between about pH 5.0 and about pH 10.0, more preferably between about pH 6.0 and about pH 10.0, more preferably between about pH 5.0 and about pH 7.0, more preferably between about pH 5.0 and about pH 7.0, more preferably between about pH 6.5 and about pH 7.0, e.g. at about pH 7.0 (i.e. neutral pH). In one embodiment preferably the process is carried out between about pH 5.5 and pH 6.0. In another embodiment, the process is carried out between about pH 6.0 to pH 6.8, e.g. between about pH 6.3 and pH 6.5, preferably about pH 6.4.
Suitably the water content of the oil when incubated (or admixed) with the enzyme is between about 0.5 to about 5% water, more preferably between about 1 to about 3% and more preferably between about 1.5 and about 2% by weight. In specific embodiments, the water content may be, for example, 0.7% to 1.2%, e.g. about 1% by weight; or 1.7% to 2.2%, e.g. about 2% by weight.
When an immobilised enzyme is used, suitably the water activity of the immobilised enzyme may be in the range of about 0.2 to about 0.98, preferably between about 0.4 to about 0.9, more preferably between about 0.6 to about 0.8.
Oil Separation
Following an enzymatic treatment step using an enzyme according to the present invention, in one embodiment the treated liquid (e.g. oil) is separated with an appropriate means such as a centrifugal separator and the processed oil is obtained. Upon completion of the enzyme treatment, if necessary, the processed oil can be additionally washed with water or organic or inorganic acid such as, e.g., acetic acid, citric acid, phosphoric acid, succinic acid, and the like, or with salt solutions.
Chlorophyll and/or Chlorophyll Derivative Removal
The process of the present invention involving an enzyme treatment typically reduces the level of chlorophyll and/or chlorophyll derivatives in the oil. For example, the process may reduce the concentration of chlorophyll, pheophytin and/or pyropheophytin by at least 5%, at least 10%, at least 20%, at least 30%, at least 40%, at least 50%, at least 60%, at least 70%, at least 80%, at least 90%, at least 95% or at least 99%, compared to the concentration of chlorophyll, pheophytin and/or pyropheophytin (by weight) present in the oil before treatment. Thus in particular embodiments, the concentration of chlorophyll and/or chlorophyll derivatives in the oil after treatment may be less than 100, less than 50, less than 30, less than 10, less than 5, less than 1, less than 0.5, less than 0.1 mg/kg or less than 0.02 mg/kg, based on the total weight of the oil.
Further Processing Steps
In a typical plant oil processing method, oil is extracted in hexane, the crude vegetable oil is degummed, optionally caustic neutralized, bleached using, e.g. clay adsorption with subsequent clay disposal, and deodorized to produce refined, bleached and deodorized or RBD oil (see
In embodiments of the present invention, an enzymatic reaction involving application of the enzyme capable of hydrolyzing chlorophyll or a chlorophyll derivative is preferably performed at specific stages in this process. In particular, according to the present invention the enzyme is contacted with the oil in the presence of at least 0.1% by weight phospholipid and preferably less than 0.2% by weight lysophospholipid. Although the level of phospholipid and lysophospholipid in the oil at different stages of the process will vary depending on the nature and source of the oil, it is generally preferred to contact the enzyme with the oil at a stage in the process before phospholipid levels are substantially reduced and before lysophospholipid levels are elevated.
Preferred stages of the process for using the enzyme according to the present process are shown in
In some embodiments, the enzyme may be contacted with the oil after water degumming (e.g. the enzyme is added to water-degummed oil), provided that the enzymatic hydrolysis of chlorophyll and chlorophyll derivatives is performed before a total degumming step, e.g. before addition of acid and caustic neutralization. This is shown by a dashed line in
Further processing steps, after treatment with the enzyme, may assist in removal of the products of enzymatic hydrolysis of chlorophyll and/or chlorophyll derivatives. For instance, further processing steps may remove chlorophyllide, pheophorbide, pyropheophorbide and/or phytol.
Degumming
The degumming step in oil refining serves to separate phosphatides by the addition of water. The material precipitated by degumming is separated and further processed to mixtures of lecithins. The commercial lecithins, such as soybean lecithin and sunflower lecithin, are semi-solid or very viscous materials. They consist of a mixture of polar lipids, primarily phospholipids such as phosphatidylcholine with a minor component of triglycerides. Thus as used herein, the term “degumming” means the refining of oil by removing phospholipids from the oil. In some embodiments, degumming may comprise a step of converting phosphatides (such as lecithin and phospholipids) into hydratable phosphatides.
The process of the invention can be used with any degumming procedure, particularly in embodiments where the chlorophyll- or chlorophyll derivative-hydrolyzing enzyme is contacted with the oil before the degumming step. Thus suitable degumming methods include water degumming, ALCON oil degumming (e.g., for soybeans), safinco degumming, “super degumming,” UF degumming, TOP degumming, uni-degumming, dry degumming and ENZYMAX™ degumming. See e.g. U.S. Pat. Nos. 6,355,693; 6,162,623; 6,103,505; 6,001,640; 5,558,781; 5,264,367, 5,558,781; 5,288,619; 5,264,367; 6,001,640; 6,376,689; WO 0229022; WO 98118912; and the like. Various degumming procedures incorporated by the methods of the invention are described in Bockisch, M. (1998), Fats and Oils Handbook, The extraction of Vegetable Oils (Chapter 5), 345-445, AOCS Press, Champaign, Ill.
Water degumming typically refers to a step in which the oil is incubated with water (e.g. 1 to 5% by weight) in order to remove phosphatides. Typically water degumming may be performed at elevated temperature, e.g. at 50 to 90° C. The oil/water mixture may be agitated for e.g. 5 to 60 minutes to allow separation of the phosphatides into the water phase, which is then removed from the oil.
Acid degumming may also be perfoi med. For example, oil may be contacted with acid (e.g. 0.1 to 0.5% of a 50% solution of citric or malic acid) at 60 to 70° C., mixed, contacted with 1 to 5% water and cooled to 25 to 45° C.
Further suitable degumming procedures for use with the process of the present invention are described in WO 2006/008508. In one embodiment the process comprises contacting the chlorophyll- or chlorophyll derivative-hydrolyzing enzyme with the oil and subsequently performing an enzymatic degumming step using an acyltransferase as described in WO 2006/008508. Acyltransferases suitable for use in the process are also described in WO 2004/064537, WO 2004/064987 and WO 2009/024736. Any enzyme having acyltransferase activity (generally classified as E.C.2.3.1) may be used, particularly enzymes comprising the amino acid sequence motif GDSX, wherein X is one or more of the following amino acid residues: L, A, V, I, F, Y, H, Q, T, N, M or S. In one embodiment, acyltransferase is a mutant Aeromonas salmonicida mature lipid acyltransferase (GCAT) with a mutation of Asn80Asp, e.g. an acyltransferase comprising the amino acid sequence of SEQ ID NO:23 after undergoing post-translational modification (see
In another embodiment, the process comprises a degumming step using a phospholipase. Any enzyme having e.g. a phospholipase A1 (E.C.3.1.1.32) or a phospholipase A2 (E.C.3.1.1.4) activity may be used, for example Lecitase Ultra® or pancreatic phospholipase A2 (Novozymes, Denmark). In one embodiment the process comprises contacting the chlorophyll- or chlorophyll derivative-hydrolyzing enzyme with the oil and subsequently performing an enzymatic degumming step using a phospholipase, for example using a degumming step as described in US 5,264,367, EP 0622446, WO 00/32758 or Clausen (2001) “Enzymatic oil degumming by a novel microbial phospholipase,” Eur. J. Lipid Sci. Technol. 103:333-340.
In embodiments where the degumming step is performed simultaneously with the chlorophyll or chlorophyll derivative hydrolysis step, preferably the degumming process does not produce lysophospholipids. For example, in these embodiments the degumming step may be a water degumming step. In another such embodiment, an enzymatic degumming step using an enzyme such as phospholipase C (IUB 3.1.4.1) may be used. Polypeptides having phospholipase C activity which are may be used in a degumming step are disclosed, for example, in WO2008143679, WO2007092314, WO2007055735, WO2006009676 and WO03089620. A suitable phospholipase C for use in the present invention is Purifine®, available from Verenium Corporation, Cambridge, Mass.
Acid Treatment/Caustic Neutralization
In some embodiments, an acid treatment/caustic neutralization step may be performed in order to further reduce phospholipid levels in the oil after water degumming. In another embodiment, a single degumming step comprising acid treatment/caustic neutralization may be performed. Such methods are typically referred to as total degumming or alkali refining.
It has been found that an acid treatment/caustic neutralization step is particularly effective in removing products of the enzymatic hydrolysis of chlorophyll, e.g. chlorophyllide, pheophorbide and pyropheophorbide. Thus this step may be performed at any stage in the process after the enzyme treatment step. For example, such a step may comprise addition of an acid such as phosphoric acid followed by neutralization with an alkali such as sodium hydroxide. Following an acid/caustic neutralization treatment compounds such as chlorophyllide, pheophorbide and pyropheophorbide are extracted from the oil in an aqueous phase.
In such methods, the oil is typically first contacted with 0.05 to 0.5% by weight of concentrated phosphoric acid, e.g. at a temperature of 50 to 90° C., and mixed to help precipitate phosphatides. The contact time may be, e.g. 10 seconds to 30 minutes. Subsequently an aqueous solution of an alkali (e.g. 1 to 20% aqueous sodium hydroxide) is added, e.g. at a temperature of 50 to 90° C., followed by incubation and mixing for 10 seconds to 30 minutes. The oil may then be heated to about 90° C. and the aqueous soap phase separated from the oil by centrifugation.
Optionally, further wash steps with e.g. sodium hydroxide or water may also be performed.
Chlorophyllide, Pheophorbide and Pyropheophorbide Removal
Thus the method of the present invention may optionally involve a step of removing phytol-free derivatives of chlorophyll such as chlorophyllide, pheophorbide and pyropheophorbide. Such products may be present in the composition due to the hydrolysis of chlorophyll or a chlorophyll derivative by the enzyme of the invention, or may be present naturally, as a contaminant, or as an undesired component in a processed product. Pyropheophorbide may also be present in the composition due to the breakdown of pheophorbide, which may itself be produced by the activity of an enzyme having pheophytinase activity on pheophytin, or pheophorbide may be formed from chlorophyllide following the action of chlorophyllase on chlorophyll (see
In one embodiment the process of the present invention reduces the level of chlorophyllide, pheophorbide and/or pyropheophorbide in the oil, compared to either or both of the levels before and after enzyme treatment. Thus in some embodiments the chlorophyllide, pheophorbide and/or pyropheophorbide concentration may increase after enzyme treatment. Typically the process involves a step of removing chlorophyllide, pheophorbide and/or pyropheophorbide such that the concentration of such products is lower than after enzyme treatment. Preferably the chlorophyllide, pheophorbide and/or pyropheophorbide produced by this enzymatic step is removed from the oil, such that the final level of these products in the oil is lower than before enzyme treatment.
For example, the process may reduce the concentration of chlorophyllide, pheophorbide and/or pyropheophorbide by at least 5%, at least 10%, at least 20%, at least 30%, at least 40%, at least 50%, at least 60%, at least 70%, at least 80%, at least 90%, at least 95% or at least 99%, compared to the concentration of chlorophyllide, pheophorbide and/or pyropheophorbide (by weight) present in the oil before the chlorophyllide, pheophorbide and/or pyropheophorbide removal step, i.e. before or after enzyme treatment. Thus in particular embodiments, the chlorophyllide, pheophorbide and/or pyropheophorbide concentration in the oil after the removal step may be less than 100, less than 50, less than 30, less than 10, less than 5, less than 1, less than 0.5, less than 0.1 mg/kg, or less than 0.02 mg/kg, based on the total weight of the composition (e.g a vegetable oil).
It is an advantage of the present process that reaction products such as chlorophyllide, pheophorbide and/or pyropheophorbide may be simply and easily removed from the oil by a step such as acid treatment/caustic neutralization. Thus in preferred embodiments chlorophyll and chlorophyll derivatives may be substantially removed from the oil without the need for further processing steps such as clay and/or silica treatment and deodorization (as indicated by the dashed boxes shown in
Clay Treatment
It is particularly preferred that the process does not comprise a clay treatment step. Avoiding the use of clay is advantageous for the reasons described earlier, in particular the reduction in cost, the reduced losses of oil through adherence to the clay and the increased retention of useful compounds such as carotenoids and tocopherol.
In some embodiments, the process may be performed with no clay treatment step and no deodorization step, which results in an increased concentration of such useful compounds in the refined oil, compared to a process involving clay treatment.
Silica Treatment
Although not always required, in some embodiments the process may comprise a step of silica treatment, preferably subsequent to the enzyme treatment. For example, the method may comprise use of an adsorbent-free or reduced adsorbent silica refining devices and processes, which are known in the art, e.g., using TriSyl Silica Refining Processes (Grace Davison, Columbia, Md.), or, SORBSIL R™ silicas (INEOS Silicas, Joliet, Ill.).
The silica treatment step may be used to remove any remaining chlorophyllide, pheophorbide and/or pyropheophorbide or other polar components in the oil. For example, in some embodiments a silica treatment step may be used as an alternative to an acid treatment/caustic neutralization (total degumming or alkali refining) step.
In one embodiment the process comprises a two-stage silica treatment, e.g. comprising two silica treatment steps separated by a separation step in which the silica is removed, e.g. a filtration step. The silica treatment may be performed at elevated temperature, e.g. at above about 30° C., more preferably about 50 to 150° C., about 70 to 110° C., about 80 to 100° C. or about 85 to 95° C. , most preferably about 90° C.
Deodorization
In some embodiments, the process may comprise a deodorization step, typically as the final refining step in the process. In one embodiment, deodorization refers to steam distillation of the oil, which typically removes volatile odor and flavor compounds, tocopherol, sterols, stanols, carotenoids and other nutrients. Typically the oil is heated to 220 to 260° C. under low pressure (e.g. 0.1 to 1 kPa) to exclude air. Steam (e.g. 1-3% by weight) is blown through the oil to remove volatile compounds, for example for 15 to 120 minutes. The aqueous distillate may be collected.
In another embodiment, deodorization may be performed using an inert gas (e.g. nitrogen) instead of steam. Thus the deodoriztion step may comprise bubble refining or sparging with an inert gas (e.g. nitrogen), for example as described by A. V. Tsiadi et al. in “Nitrogen bubble refining of sunflower oil in shallow pools”, Journal of the American Oil Chemists' Society (2001), Volume 78 (4), pages 381-385. The gaseous phase which has passed through the oil may be collected and optionally condensed, and/or volatile compounds extracted therefrom into an aqueous phase.
In some embodiments, the process of the present invention is performed with no clay treatment but comprising a deodorization step. Useful compounds (e.g. carotenoids, sterols, stanols and tocopherol) may be at least partially extracted from the oil in a distillate (e.g. an aqueous or nitrogenous distillate) obtained from the deodorization step. This distillate provides a valuable source of compounds such as carotenoids and tocopherol, which may be at least partially lost by entrainment in a process comprising clay treatment.
The loss of tocopherol during bleaching depends on bleaching conditions and the type of clay applied, but 20-40% removal of tocopherol in the bleaching step has been reported (K. Boki, M, Kubo, T. Wada, and T. Tamura, ibid., 69, 323 (1992)). During processing of soy bean oil a loss of 13% tocopherol in the bleaching step has been reported (S. Ramamurthi, A. R. McCurdy, and R. T. Tyler, in S. S. Koseoglu, K. C. Rhee, and R. F. Wilson, eds., Proc. World Conf. Oilseed Edible Oils Process, vol. 1, AOCS Press, Champaign, Ill., 1998, pp. 130-134).
Carotenoids may be removed from the oil during deodorization in both clay-treated and non-clay-treated oil. Typically the removal of coloured carotenoids is controlled in order to produce an oil having a predetermined colour within a specified range of values. The level of carotenoids and other volatile compounds in the refined oil can be varied by modifying the deodorization step. For instance, in an embodiment where it is desired to retain a higher concentration of carotenoids in the oil, the deodorization step may be performed at a lower temperature (e.g. using steam at 200° C. or below). In such embodiments it is particularly preferable to avoid a clay treatment step, since this will result in a higher concentration of carotenoids in the refined oil.
Further Enzyme Treatments
In further aspects, the processes of the invention further comprise use of lipid acyltransferases, phospholipases, proteases, phosphatases, phytases, xylanases, amylases (e.g. α-amylases), glucanases, polygalacturonases, galactolipases, cellulases, hemicellulases, pectinases and other plant cell wall degrading enzymes, as well as mixed enzyme preparations and cell lysates. In alternative aspects, the processes of the invention can be practiced in conjunction with other processes, e.g., enzymatic treatments, e.g., with carbohydrases, including cellulase, hemicellulase and other side degrading activities, or, chemical processes, e.g., hexane extraction of soybean oil. In one embodiment the method of the present invention can be practiced in combination with a method as defined in WO 2006031699.
The invention will now be further illustrated with reference to the following non-limiting examples.
Cloning and Expression of a Chlorophyllase from Triticum aestivum (Wheat) in Bacillus subtilis
A nucleotide sequence (SEQ ID No. 3) encoding a wheat chlorophyllase (SEQ. ID No. 2, hereinafter wheat chlase) was expressed in Bacillus subtilis with the signal peptide of a B. subtilis alkaline protease (aprE) (see
The construct TRI_CHL contains 20 nucleotides with a BssHII restriction site upstream to the wheat chlase coding region to allow fusion to the aprE signal sequence and a PacI restriction site following the coding region for cloning into the bacillus expression vector pBNppt.
The construct TRI_CHL was digested with BssHII and PacI and ligated with T4 DNA ligase into BssHII and PacI digested pBNppt.
The ligation mixture was transformed into E. coli TOP10 cells. The sequence of the BssHII and Pac insert containing the TRI_CHL gene was confirmed by DNA sequencing (DNA Technology A/S, Risskov, Denmark) and one of the correct plasmid clones was designated pBN-TRI_CHL (
One neomycin resistant (neoR) transformant was selected and used for expression of the wheat chlase.
Cloning and Expression of a Cchlorophyllase from Chlamydomonas reinhardtii (Green Algae) in Bacillus subtilis
A nucleotide sequence (SEQ ID No. 5) encoding a Chlamydomonas chloryphyllase (SEQ. ID No. 4, hereinafter chlamy chlase) was expressed in Bacillus subtilis with the signal peptide of a B. subtilis alkaline protease (aprE) (see
The construct CHL_CHL contains 20 nucleotides with a BssHII restriction site upstream to the chlamy chlase coding region to allow fusion to the aprE signal sequence and a Pad restriction site following the coding region for cloning into the bacillus expression vector pBNppt.
The construct CHL_CHL was digested with BssHII and Pad and ligated with T4 DNA ligase into BssHII and PacI digested pBNppt.
The ligation mixture was transformed into E. coli TOP10 cells. The sequence of the BssHII and Pac insert containing the CHL CHL gene was confirmed by DNA sequencing (DNA Technology A/S, Risskov, Denmark) and one of the correct plasmid clones was designated pBN-CHL_CHL (
One neomycin resistant (neoR) transformant was selected and used for expression of the chlamy chlase.
Effect of Surfactants on Chlorophyllase Activity in Plant Oil
Activity of a chlorophyllase from Arabidopsis thaliana having the sequence of SEQ ID NO:1 was tested in refined rapeseed oil with the addition of different surfactants, including soya lecithin. Samples 1 to 6 were prepared comprising the components defined in Table 1:
Refined rapeseed oil and surfactant was heated to 45° C. with agitation. Chlorophyll, buffer and chlorophyllase were added. The samples were incubated with agitation for 180 minutes and 1 nil sample was taken out and centrifuged for 3 minutes at 3000 ref.
The oil phase was measured by fluorescence spectroscopy (excitation at 410 nm, emission at 672 nm) and the amount of chlorophyll was quantified (Table 2) from a calibration curve made from measurement of refined rapeseed oil to which a known concentration of chlorophyll had been added.
The results in Table 2 clearly indicate that different surfactants have a strong impact on the activity of chlorophyllase. Lecithin has a strong positive effect on the chlorophyllase activity and thus on the reduction of chlorophyll in oil. Sorbitan monooleate also has a positive effect on the chlorophyllase activity, but the chlorophyllase activity is very modest when sorbitan trioleate is added to the oil.
As can be seen from
Effect of Fefining on Chlorophyllase Activity in Plant Oil
As shown in Example 3, surfactants influence chlorophyllase activity on refined oil. At different stages in the oil refining process, the amount of surfactant (particularly lecithin) may vary, thereby influencing chlorophyllase activity.
In the following example chlorophyllase activity was tested in a refined oil and in a combination of refined oil and crude soya oil according to the recipe in Table 3:
Oil was heated to 40° C. Chlorophyll, water and enzyme were added and the sample was homogenized with high shear mixing for 20 second and incubated at 40° C. with magnetic stirring. After 90 minutes the samples were heated to 97° C. for 10 minutes and centrifuged at 1780 rcf for 3 minutes.
The samples were evaluated visually as shown in
In sample 7 (a 1:1 mixture of refined oil:crude soya oil with chlorophyllase treatment) it is very clear that the green colour enters into the water phase and the water phase is very different from sample 5 where no chlorophyllase was added.
The results show that chlorophyllase is only active in hydrolyzing chlorophyll in the oil samples containing crude soya oil. This suggests that surfactants present in the crude soya oil facilitated the chlorophyllase reaction. The crude soya oil contains a high level of surfactant in the form of 2-3% lecithin (principally phospholipids). In the refined oil there are almost no surfactants and therefore no chlorophyllase activity is observed.
Effect of Lecithin and Acyltransferase on Activity of Chlorophyllase in Oil
Examples 3 and 4 suggest that surfactants like lecithin (which comprises phospholipids) are important for the activity of a chlorophyllase. Lecithin is present at varying levels in some crude plant oils. It is a natural constituent of crude plant oils like soya oil and rapeseed oil, but during the oil refining process lecithin is typically removed from the oil by a degumming process. During the degumming step lecithin may be removed enzymatically by enzymes such as phospholipases. If chlorophyllase activity is dependent on the presence of lecithin, lecithin modification by enzymes will impact on the chlorophyllase activity. It is therefore of importance for efficient chlorophyll removal that the chlorophyllase is used in the presence of a minimum level of lecithin. This may be influenced by the level of lecithin naturally present in the particular oil, a point during the refining process at which chlorophyllase is applied, and the nature of the degumming step.
In the following example a crude oil was water degun'imed without and with a lipid acyltransferase (LysoMax Oil® from Danisco A/S). LysoMax Oil® is an Aeromonas salmonicida mature lipid acyltransferase (GCAT) with a mutation of Asn80Asp, comprising the amino acid sequence of SEQ ID NO:23 (see
Water degumming was conducted with recipe in shown in Table 4:
Crude oil was heated to 55° C. Water and enzyme were added and mixed with high shear mixing for 20 seconds followed by incubation with magnetic stirring. After 30 minutes incubation the samples were heated to 97° C. for 10 minutes and centrifuged at 1780 ref for 3 minutes. The oil phase and the gum phase for the two experiments were isolated. The gum phases were dried on a rotary evaporator.
A chlorophyllase from Triticum (see Example 1) was tested in a water degumming (WDG) process using the oil and dried gum phase according to recipes in table 5. Oil and dried gum was heated to 55° C. with agitation. Water and chlorophyllase were added. The samples were incubated at 65° C. for 4 hours. The enzyme was inactivated by heating to 97° C. for 10 minutes followed by centrifugation at 1780 ref for 3 minutes.
The oil phases were isolated and analysed by HPLC with fluorescence detection. The fluorescence signal RFU was calculated based on the same amount of oil with results in table 6 and
For comparison the crude rapeseed oil without chlorophyllase treatment was analysed with the following results:
The results from table 6 clearly indicate an effect of lecithin and enzyme modified lecithin on the activity of chlorophyllase. In the sample of crude oil, chlorophyllase is clearly more active than in the sample of water degummed oil (WDG). It is also observed that addition of lecithin to water degummed oil increases the activity of chlorophyllase, and there is a dosage response of adding lecithin from 0.2 to 2% added lecithin. The water degummed oil contains about 0.3% lecithin, which is consistent with the fact that chlorophyllase is somewhat active in the water degummed oil without addition of extra lecithin. As shown in Example 4, chlorophyllase activity is very low in refined rapeseed oil, so the results suggest that the remaining lecithin in water degummed oil has a clear impact on the chlorophyllase activity.
Addition of LysoMax Oil® (lipid acyl transferase from Danisco A/S) modified lecithin to water degummed oil has a strong impact on the chlorophyllase activity. Even a low level of enzyme modified lecithin (0.2%) has a strong negative impact on the activity of the chlorophyllase enzyme, and with addition of 2% enzyme modified lecithin the chlorophyllase activity is almost completely stopped.
When lysolecithin was added to chlorophyllase in an aqueous system comprising Triton X100 as surfactant, no reduction in chlorophyllase activity was observed (results not shown). This aqueous system differs markedly in terms of physical properties with an oil system containing only 3% water. The results suggest that lysophospholipids form different mesomorphic phases and thus prevent the interaction between substrate (e.g. pheophytin) and enzyme (chlorophyllase).
Effect of Chlorophyllase and Phospholipases in Water Degumming of Rapeseed Oil
The results in Example 5 indicate that enzyme modified lecithin has a strong impact on Triticum chlorophyllase activity. It was therefore investigated how chlorophyllases work in water degumming in combination with different phospholipases/acyltransferase.
In this experiment chlorophyllase from Triticum (see Example 1) and Chlamydomonas (see Example 2) were tested in combination with a LysoMax Oil® (lipid acyltransferase from Danisco A/S), a phopholipase A1 (PLA1, Lecitase Ultra®) and a phospholipase C (PLC, Purifine®).
The water degumming was conducted with the recipe shown in table 7.
Triticum CHL'ase, CoRe 20
Chlamydomonas CHL'ase
Crude rapeseed oil was heated to 55° C. Water and enzymes were added and the samples were homogenized with high shear mixing for 20 seconds, followed by agitation with a magnetic stirrer. After 4 hours incubation the samples were heated to 97° C. for 10 minutes and centrifuged at 1780 ref for 3 minutes.
Chlorophyll components of the oil phase were analyzed by HPLC with results in table 8 and
The results from table 8 clearly indicate altered activity of chlorophyllase on pheophytin in the presence of phospholipases or an acyltransferase. For comparison, in a control sample comprising no enzyme the pheophytin A in crude rapeseed oil gives a relative fluorescence value of 11.4 RFU.
When chlorophyllases are combined with acyltransferase or PLA1 the amount of pheophytin is much higher than the control comprising chlorophyllase alone, but when chlorophyllases are combined with PLC the level of pheophytin is almost equal with the control oil only treated with chlorophyllase. The experiments indicate that chlorophyllases are inhibited when used in combination with enzymes which during incubation produce lysophospholipids from phospholipids. In contrast, the chlorophyllases retain most of their original activity when used in combination with a PLC, which produces diglyceride from phospholipids.
Chlorophyllase in Total Degumming
Example 6 shows that chlorophyllase can be used during oil refining in the water degumming process. Depending on the type of oil and depending on the refining process, different types of degumming processes may be used. Thus as an alternative to a water degumming process, A plant oil may he refined without water degumming in as total degumming process or neutralization. In the following example chlorophyllase was used in a total degumming/neutralization process. In this experiment chlorophyllase is also tested in combination with acyltransferase with the recipe shown in table 9:
Crude rapeseed oil was heated to 55° C. 30% phosphoric acid was added and the sample was homogenized with high shear mixing for 10 second followed by magnetic stirring at 55° C. After 10 minutes water, NaOH and enzymes were added and incubated at 55° C. with magnetic stirring. After 4 hours the samples were heated to 97° C. for 10 minutes and centrifuged at 1780 ref for 3 minutes.
The oil phase was analysed by HPLC with results shown in table 10:
The results in table 10 confirm high activity of chlorophyllase on pheophytin in a total oil degumming process. In combination with acyltransferase the chlorophyllase activity is significantly reduced.
Oil Refining Procedure with Chlorophyllase, With and Without Bleaching
In this example a chlorophyllase gene from Triticum (called TRI_CHL, see Example 1) expressed in E. Coli is used in oil refining of crude rapeseed oil. This enzyme has activity on chlorophyll, pheophytin and pyropheophytin in oil. In the first step the oil is treated with TRI_CHL, where the chlorophyll, pheophytin and pyropheophytin is hydrolysed to chlorophyllide, pheophorbide and pyropheophorbide respectively. After TRI_CHL treatment the oil is further refined without the use of bleaching clay, and the oil is compared with the same oil refined by traditional oil refining using bleaching clay.
Oil refining procedure with chlorophyllase and without bleaching Water degumming: 175 g crude rapeseed oil is heated to 65° C. during agitation and blanketed with nitrogen. 8.75 Units (0.05 Units/g) of TRI_CHL is added together with 6.125 g (3.5%) water. The reaction mixture is homogenized with high shear mixing for 20 seconds. The sample is incubated at 65° C. with agitation and blanketed with nitrogen. After 4 hours reaction time the sample is centrifuged at 3000 rcf for 5 minutes and the water degummed oil is isolated.
Total degumming: 150 gram water degummed oil is dried by heating to 90° C. for 20 minutes. The oil is cooled to 80° C. and 0.33% phosphoric acid (30% aqueous solution) is added. The sample is homogenized by high shear mixing for 10 second and agitated for 10 minutes while cooling down to 70° C. followed by addition of 1.28% 4N NaOH . The sample is agitated for 5 minutes blanketed with nitrogen. The sample is centrifuged at 3000 rcf for 5 minutes.
NaOH wash: The oil is isolated and heated to 90° C. 4% 0.1N NaOH is added and the sample is agitated for 5 minutes. The oil is centrifuged at 3000 ref for 5 minutes.
Water washes: The isolated oil phase is heated to 50° C. and washed with 4% water with agitation for 5 minutes and centrifuged at 300 rcf for 5 minutes. The oil phase is washed once more with 4% water. The isolated oil phase is dried by heating to 100° C. under vacuum for 20 minutes.
Deodorization: The oil is deodorized at 240° C. and 0.5 mBar for 1 hour with steam stripping. The oil is polished by filtering through a glass Microfiber filter (Whatman GF/C).
Oil Refining Reference Procedure with Bleaching:
Water degumming: 175 g crude rapeseed oil is heated to 65° C. during agitation and blanketed with nitrogen. 6.125 g (3.5%) water is added. The reaction mixture is homogenized with high shear mixing for 20 seconds. The sample is incubated at 65° C. with agitation and blanketed with nitrogen. After 4 hours reaction time the sample is centrifuged at 3000 rcf for 5 minutes and the water degummed oil is isolated.
Total degumming: 150 gram water degummed oil is dried by heating to 90° C. for 20 minutes. The oil is cooled to 80° C. and 0.33% phosphoric acid (30% aqueous solution) is added. The sample is homogenized by high shear mixing for 10 second and agitated for 10 minutes while cooling down to 70° C. followed by addition of 1.28% 4N NaOH. The sample is agitated for 5 minutes blanketed with nitrogen. The sample is centrifuged at 3000 rcf for 5 minutes.
Bleaching: The oil is added 1% bleaching clay (Tonsil Optimum FF210) and heated at 90° C. under vacuum and agitation for 20 minutes. The oil is cooled to 80° C. and filtered on a buchner funnel using filter paper. The isolated oil phase is dried by heating to 100° C. under vacuum for 20 minutes.
Deodorization: The oil is deodorized at 240° C. and 0.5 mBar for 1 hour with steam stripping. The oil is polished by filtering through a glass Microfiber filter (Whatman GF/C).
Results
Crude rapeseed oil from AarhusKarlshamn was refined according to the method above using either (1) Oil refining procedure with chlorophyllase and without bleaching or (2) Oil refining reference procedure with bleaching.
The oil colour was measured according to LoviBond using Dr. Lange, LICO 200 apparatus. The results are shown in Table 11:
HPLC/MS Analysis:
Oil samples from the different processes in the oil refining were analysd by HPLC/MS and quantified relative to standards of the components with results shown in table 12:
The results from table 12 are illustrated graphically in
The results show that cholorophyllase is active on pheophytin and pyropheophytin in the oil during water degumming More than 95% of pheophytin and more than 70% of pyropheophytin are removed in the chlorophyllase treated oil. These components are hydrolyzed to phytol and pheophorbide and pyropheophorbide respectively. It is observed that after the water degumming process these two components increase in the chlorophyllase treated oil. However a large proportion of these components are washed out by alkaline treatment in the total degumming process. The subsequent washing with NaOH and water only contribute marginally to further removal of the degradation products.
Materials
In Examples 3 to 8, the following materials were generally used, except where otherwise specified:
Oil: crude extracted rapeseed oil from AarhusKarlshamn
Enzymes:
Chlorophyllase from Triticum expressed in E. coli and purified, Labelled CoRe-20 (see Example 1);
Chlorophyllase from Clamydomonas expressed in Bacillus, Labeled CoRe-31 (see Example 2);
Lipid Acyltransferase, LysoMax Oil® from Danisco A/S, e.g. comprising the amino acid sequence of SEQ ID NO:23
Phospholipase C , Purifine® from Verenium Corporation
Phospholipase A1, Lecitase Ultra® from Novozymes A/S
Emulsifiers:
Sorbitan monooleate, SMO from Danisco A/S
Sorbitan trioleate, STO from Danisco A/S
HPLC Analysis
In Examples 3 to 7, chlorophyll derivatives were in general quantified by HPLC analysis according to the following method. HPLC analysis was performed using a method in general teinis as described in “Determination of chlorophylls and carotenoids by high-performance liquid chromatography during olive lactic fermentation”, Journal of Chromatography, 585, 1991, 259-266.
The determination of pheophytin, pheophorbide, pyropheophytin and pyropheophorbide is performed by HPLC coupled to a diode array detector. The column employed in the method is packed with C18 material and the chlorophylls were separated by gradient elution. Peaks are assigned using standards of chlorophyll A and B from SigmaAldrich, e.g. based on the representative HPLC chromatogram from Journal of Chromatography, 585, 1991, 259-266 shown in
Chlorophyllase Dosage in a Water Degumming Process
Triticum chlorophyllase was tested in different dosages in water degumming of crude rapeseed oil according to the recipe in Table 13. The oil was heated to 65° C., water and enzyme was added. The sample was mixed with a high shear mixer for 20 seconds and incubated with magnetic agitation. Samples were taken out for analysis after ½, 1 and 2 hours, and heated to 97° C. for 10 minutes to inactivate the enzyme. The samples were then centrifuged at 10000 ref for 5 minutes and chlorophyll components in the oil were analysed by HPLC/MS.
Triticum chlorophyllase 14 U/ml
The HPLC results are shown in Table 14:
Each of the four chlorophyll derivatives chlorophyll a and b and pheophytin a and b exist as a pair of epimers deteiinined by the stereochemistry of H and COOCH3 around the carbon number 132 (numbering according to the IUPAC system). These are denoted a/b and a′/b′ with the prime (′) forms having S-stereochemistry and non-prime forms having R-stereochemistry.
From the results in Table 14, it is clear that the main component in this oil is pheophytin. Pheophytin is often the main green component in oil, because chlorophyll easily loses its magnesium and turns into pheophytin. Because pheophytin is the main component it is chosen to focus on this component for the analysis of the enzymatic degradation.
The effect of chlorophyllase as a function of enzyme dosage and reaction time is illustrated in
The results in Table 14 confirm the activity of Triticum chlorophyllase on degradation of chlorophyll, pheophytin and pyropheophytin. The results from the control sample without enzyme addition however reveals that chlorophyll a and b are thermally degraded, most probably because chlorophyll loses magnesium and is converted to pheophytin.
It is also observed that the amount of pyropheophytin increases as a function of time in the control sample, most probably because some of the pheophytin is converted to pyropheophytin. Formation of pyropheophytin is not preferred because the enzyme activity on this component is much lower than on pheophytin. The reaction product from hydrolysis of pyropheophytin is pyropheophorbide, which is more hydrophobic than pheophorbide and thus more difficult to wash out of the oil.
Effect of pH and Water Concentration on Chlorophyllase Activity
In this study Triticum chlorophyllase (TRI_CHL) was investigated in a total degumming process with different water dosages and different pH adjustments according to the recipe in Table 15.
The oil was heated to 55° C. and citric acid added. The sample was mixed with high shear mixing for 20 seconds followed by agitation with magnetic stirrer for 10 min. NaOH and water and enzyme was added and mixed for 20 seconds with high shear mixing. The samples were incubated with magnetic stirring for 4 hours. Samples were taken out for analysis after ½, 1 and 2 hours, and heated to 97° C. for 10 minutes to inactivate the enzyme. The samples were then centrifuged at 10000 ref for 5 minutes and the oil phase was analysed by HPLC/MS.
The effect of pH and % water on chlorophyllase activity is illustrated in
It is known that both chlorophyll and pheophytin exists in two epimer forms a and a′ (R-isomer and S-isomer), and the chlorophyllase enzyme is only active on the a-isomer form. It is known that an equilibrium exists between the two foims and the rearrangement is dependent on pH (
It is thus expected that the enzyme activity is dependent on pH because higher pH will favour the formation of the a-isomer. Based on the HPLC analysis of pheophytin a and a′ epimers it is possible to calculate the ratio of the a-epimer at different pH as shown in
Effect of Reaction Temperature on Activity of Chlorophyllase
The above mentioned experiments were conducted at 55° C. because this is the temperature typically used in water degumming with enzymes (e.g. LysoMax Oil®). Chlorophyllase from Triticum (TRI_CHL) is however known to be more heat stable, and in the following experiment the enzyme activity in oil was investigated at 65, 70 and 75° C. according to the recipe in Table 16.
Oil was heated to set point 65, 70 or 75° C. Water and enzyme was added and the sample was mixed with high shear mixing for 20 sec. and incubated with agitation at set temperature. Sample were taken out for analysis after ½, 1 and 2 hours, and heated to 97° C. for 10 minutes to inactivate the enzyme. The samples were then centrifuged at 10000 rcf for 5 minutes and the oil phase was analysed by HPLC/MS. The results were evaluated statistically using ANOVA Statgraphic software.
The effect of temperature on level of pheophytin is shown in
The results indicate that enzymatic degradation of green colour is not limited to the degradation of pheophytin but also pyropheophytin is an important component. One of the limitations is that Triticum chlorophyllase has much lower activity on pyropheophytin compared to activity on pheophytin and therefore more enzyme and/or reaction time is needed to hydrolyze this component. Another aspect is that pheophytin might be converted into pyropheophytin and it could be expected that the temperature has an impact on this.
The effect of temperature on level of pyropheophytin is shown in
Taking into account that part of chlorophyll is converted to pheophytin and pheophytin is converted to pyropheophytin, the effect of temperature on the sum of the three components was also investigated (
Mixing Conditions During Chlorophyllase Activity in Oil/Water
The enzymatic reaction of Triticum chlorophyllase (TRI_CHL) on chlorophyll in oil is conducted in a two phase oil/water reaction mixture. It could therefore be speculated that the reaction would depend on the water distribution and particle size of the water droplets. In order to investigate this in more details experiments were set up with and without high shear mixing. Also experiments were set up where enzyme and water were mixed before addition to the oil (Table 17). In all experiments 3.5% water was used.
Oil was heated to 65° C. with magnetic stirring. Enzyme and water was added. The samples were treated with high shear mixing according to Table 17 and incubated with magnetic stirring. 1 ml samples were taken out after ½, 1 and 2 hours reaction time. The samples were then centrifuged at 10000 ref for 5 minutes and the oil phase was analysed by HPLC/MS.
The results of pheophytin content are illustrated graphically in
Effect of pH in Water Degumming
Experiments shown above (Example 10) indicated that the activity of chlorophyllase and also the rearrangement of pheophytin a′ to pheophytin a, was dependent on pH. In the following experiment, the water degumming process was conducted both without pH adjustment and with pH adjustment with NaOH or with citrate buffer. In one experiment an acyltransferase was also tested in combination with chlorophyllase. The oil was heated to 65° C. and water NaOH/buffer and enzyme was added.
The samples were mixed with Ultra Turrax for 20 sec. and incubated at 65° C. with magnetic stirring. Samples were taken out after ½, 1, 2 and 4 hours reaction time. The samples were heated to 95° C. for 10 minutes to inactivate the enzyme, and centrifuged at 10000 rcf for 5 minutes and the oil phase analysed by HPLC/MS.
In
In
Although it is very important that the enzyme is active on pheophytin, it is also important for the green colour that the process can remove the other colour components including pyropheophytin.
In
Effect of pH on Chlorophyllase Activity in Water Degumming of Oil
The results reported above indicate the effect of pH with regard to the enzyme activity and the rearrangement of pheophytin a′ to pheophytin a. Higher pH in the process also seems to have an impact on the conversion of pheophytin to pyropheophytin. In this study the pH was further investigated by narrowing the range of pH for the water degumming trials with Triticum chlorophyllase (TRI_CHL). The experiments were conducted according to Table 19.
The oil was heated to 65° C. and water, NaOH and enzyme was added. The samples were mixed with Ultra Turrax for 20 sec. and incubated at 65° C. with magnetic stirring. Samples were taken out after ½, 1, 2 and 4 hours reaction time. The samples were heated to 95° C. for 10 minutes to inactivate the enzyme, and centrifuged at 10000 rcf for 5 minutes and the oil phase was analysed by HPLC/MS.
The effect of adding NaOH and adjusting the pH has an impact on the ability of the enzyme to degrade pheophytin (see
A possible explanation for the effect of pH on activity of chlorophyllase is the fact that the enzyme is only active on pheophytin a epimer (R-isomer) and not on pheophytin a′ epimer (the S-isomer). The graphs in
Triticum chlorophyllase has much lower activity on pyropheophytin than on pheophytin. In the reaction of chlorophyllase with oil it is therefore also important that the process is optimized to produce as low as possible amount of pyropheophytin. In
The results clearly show a decrease in pyropheophytin as a function of reaction time, but it is also observed that sample with higher pH contain more pyropheophytin. This can be explained by the conversion of pheophytin to pyropheophytin, which is promoted by higher pH.
In the selection of optimal pH condition for the enzymatic degradation of chlorophyll components it is important to not only look at the enzyme kinetics but also look at the different epimers of pheophytin and the conversion of pheophytin to pyropheophytin. In
The results in
During sample preparation of samples for HPLC/MS analysis the samples were centrifuged and the oil phase was analysed. The reaction products for the hydrolysis of pheophytin will then be distributed between the oil and the water phase. The residual amount of pheophorbide in the oil phase as a function of pH is illustrated in
Effect of pH on Chlorophyllase Activity in Total Degumming Process
In the examples above, it was observed that it could be beneficial to adjust the pH in the water degumming process when using Triticum chlorophyllase (TRI_CHL). In the total degumming process, acid and alkali are always added during the process. In the following experiments the effect of pH on Triticum chlorophyllase activity in the total degumming process was investigated by first treating the oil with citric acid followed by addition of different amounts of NaOH according to Table 20.
The oil was heated to 65° C. and citric acid was added. The samples were mixed with Ultra Turrax for 20 sec. and incubated at 65° C. with magnetic stirring for 10 minutes. NaOH, water and enzyme was added, and the samples were mixed with Ultra Turrax for 20 seconds, followed by incubation at 65° C. with magnetic stirring. Samples were taken out after ½, 1 and 2 hours reaction time. The samples were heated to 95° C. for 10 minutes to inactivate the enzyme, and centrifuged at 10000 rcf for 5 minutes and the oil phase analysed by HPLC/MS.
In this total degumming example, the same trend is observed as in the water degumming process. That is, Triticum chlorophyllase is more active on pheophytin when increasing the pH from 4 to 6.6, which again is linked to the amount of the two epimer forms of pheophytin. The experiments mentioned above with water degumming was conducted with the same enzyme dosage and oil as in this total degumming process, and therefore the results of pheophytin degradation after 2 hr. reaction time as a function of pH in the two processes were compared as shown in
Effect of Water Content and pH on Chlorophyllase Activity in Oil
Earlier studies had shown that Triticum chlorophyllase (TRI_CHL) needed at least 1.5% water in oil for good activity on pheophytin. Under certain conditions it could however be preferred to use a lower water content. In the following experiments the water degumming process was conducted with 1 and 2% water and with different NaOH addition as shown in Table 21.
The process was conducted according to standard conditions mentioned in Example 14 and samples taken out after 2 and 4 hours were analysed by HPLC/MS.
The effect of pH and water contents on the amount of pheophytin in chlorophyllase treated oil is illustrated in
Optimizing Temperature for Chlorophyllase Treatment of Oil
Studies have shown that Triticum chlorophyllase is active in oil at temperatures above 70° C. At 70° C. the enzyme has its maximum activity but at this temperature the conversion of pheophytin to pyropheophytin increases significantly. Earlier studies concluded that reaction temperature of 65° C. was better than 70° C. In this study the reaction temperature was further investigated by running the water degumming and enzyme reaction process at 60 and 65° C. with variation in enzyme dosage and pH adjustment according to experiments shown in Tables 22a and 22b.
The oil was heated to 65° C./60° C. NaOH, water and enzyme was added, and the samples were mixed with Ultra Turrax for 20 seconds, followed by incubation with magnetic stirring. Samples were taken out after 2 and 4 hours reaction time. The samples were heated to 95° C. for 10 minutes to inactivate the enzyme, and centrifuged at 10000 ref for 5 minutes and the oil phase analysed by HPLC/MS. The results are graphically illustrated in
The results in
There are also some indication that the level of pyropheophytin is lower at 60° C. (
Conclusion
Triticum chlorophyllase was shown to be active on the three main chlorophyll components, chlorophyll, pheophytin and pyropheophytin in an oil system. The enzyme activity was dependent of a number of process parameters including temperature, pH, mixing, %water and reaction time.
The experiments showed that pH 6.3 to 6.5 was the best range for the activity of Triticum chlorophyllase because the enzyme is only active on the pheophytin a epimer. At pH 6.3-6.5 the rearrangement of epimer a′ to epimer a can take place in the process. At higher pH even stronger rearrangement of pheophytin a′ to a is observed, but it is also observed that at pH higher than 6.5 more pyropheophytin is produced from pheophytin. This is not preferred because Triticum chlorophyllase is less active on pyropheophytin.
The conversion of pheophytin to pyropheophytin was also found to be dependent on temperature. At 70° C. and above significantly more pyropheophytin is produced from pheophytin and this is not preferred. The experiments showed that the optimum temperature for Triticum chlorophyllase was 60° C. which is the best compromise between enzyme kinetic and conversion of pheophytin to pyropheophytin.
In a normal water degumming process, typically 2% water is used and experiments showed that Triticum chlorophyllase was very active at 2% water, It was found that the enzyme was even more active at 1% water. This lower water concentration could in some instances be advantageous, if the viscosity of the gum phase coming out of this process is not too high for proper handling and pumping.
All publications mentioned in the above specification are herein incorporated by reference. Various modifications and variations of the described methods and system of the present invention will be apparent to those skilled in the art without departing from the scope and spirit of the present invention. Although the present invention has been described in connection with specific preferred embodiments, it should be understood that the invention as claimed should not be unduly limited to such specific embodiments. Indeed, various modifications of the described modes for carrying out the invention which are obvious to those skilled in biochemistry and biotechnology or related fields are intended to be within the scope of the following claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10156412.8 | Mar 2010 | EP | regional |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/IB2011/050742 | 2/23/2011 | WO | 00 | 9/12/2012 |
| Number | Date | Country | |
|---|---|---|---|
| 61313194 | Mar 2010 | US |
