Patent Application
20190338259
This application includes a sequence listing which has been submitted electronically in ASCII format and is hereby incorporated by reference in its entirety. This ASCII copy, created on Jun. 23, 2019, is named 2019-06-23_ZMGNP007US_SeqList_ST25.txt and is 327,680 bytes in size.
The present disclosure relates generally to the area of engineering microbes for production of (6E)-8-hydroxygeraniol by fermentation.
(6E)-8-hydroxygeraniol (8-hydroxygeraniol) is an acyclic monoterpene known to exist in nature. A method for the production of terpene alcohols by chemical synthesis is known (U.S. Pat. No. 4,107,219). (6E)-8-hydroxygeraniol is derived from the mevalonate biosynthesis pathway, based on the core metabolite precursor acetyl-CoA (
The disclosure provides engineered microbial cells, cultures of the microbial cells, and methods for the production of (6E)-8-hydroxygeraniol, including the following:
An engineered microbial cell, wherein the engineered microbial cell expresses: (a) a non-native geranyl diphosphate diphosphatase (geraniol synthase); and (b) a non-native geraniol-8-hydroxylase; wherein the engineered microbial cell produces (6E)-8-hydroxygeraniol.
The engineered microbial cell of embodiment 1, wherein the engineered microbial cell includes increased activity of one or more upstream (6E)-8-hydroxygeraniol pathway enzyme(s) or of a regulator of upstream pathway activity, said increased activity being increased relative to a control cell.
The engineered microbial cell of embodiment 2, wherein the one or more upstream (6E)-8-hydroxygeraniol pathway enzyme(s) are selected from the group consisting of ATP-citrate synthase, an acetyl-CoA synthetase, a thiolase, a hydroxymethylglutaryl coenzyme A synthase (HMG-CoA synthase), a hydroxymethylglutaryl coenzyme A reductase (HMG-CoA reductase), a mevalonate kinase, a phosphomevalonate kinase, a diphosphomevalonate decarboxylase, an isopentenyl-diphosphate delta-isomerase, and a geranyl diphosphate synthase.
The engineered microbial cell of embodiment 3, wherein the one or more upstream (6E)-8-hydroxygeraniol pathway enzyme(s) comprise the isopentenyl-diphosphate delta-isomerase.
The engineered microbial cell of any one of embodiments 1-4, wherein the engineered microbial cell includes reduced activity of one or more enzyme(s) that consume one or more (6E)-8-hydroxygeraniol pathway precursors, said reduced activity being reduced relative to a control cell.
The engineered microbial cell of embodiment 5, wherein the one or more enzyme(s) that consume one or more (6E)-8-hydroxygeraniol pathway precursors comprise a bifunctional (2E,6E)-farnesyl diphosphate synthase/dimethylallyltranstransferase and/or a geranyl pyrophosphate synthase.
The engineered microbial cell of any one of embodiments 1-6, wherein the engineered microbial cell additionally expresses a feedback-deregulated HMG-CoA reductase.
The engineered microbial cell of any one of embodiments 1-7, wherein the engineered microbial cell includes increased availability of acetyl-CoA due to a higher rate of acetyl-CoA synthesis and/or a lower rate of acetyl-CoA degradation, relative to a control cell.
An engineered microbial cell, wherein the engineered microbial cell includes: (a) means for expressing a non-native native geranyl diphosphate diphosphatase (geraniol synthase); and (b) means for expressing a non-native geraniol-8-hydroxylase; wherein the engineered microbial cell produces (6E)-8-hydroxygeraniol.
The engineered microbial cell of embodiment 9, wherein the engineered microbial cell includes means for increasing the activity of one or more upstream (6E)-8-hydroxygeraniol pathway enzyme(s) or of a regulator of upstream pathway activity.
The engineered microbial cell of embodiment 10, wherein the one or more upstream (6E)-8-hydroxygeraniol pathway enzyme(s) are selected from the group consisting of ATP-citrate synthase, an acetyl-CoA synthetase, a thiolase, a hydroxymethylglutaryl coenzyme A synthase (HMG-CoA synthase), a hydroxymethylglutaryl coenzyme A reductase (HMG-CoA reductase), a mevalonate kinase, a phosphomevalonate kinase, a diphosphomevalonate decarboxylase, an isopentenyl-diphosphate delta-isomerase, and a geranyl diphosphate synthase.
The engineered microbial cell of embodiment 11, wherein the one or more upstream (6E)-8-hydroxygeraniol pathway enzyme(s) comprise the isopentenyl-diphosphate delta-isomerase.
The engineered microbial cell of any one of embodiments 9-12, wherein the engineered microbial cell includes means for reducing the activity of one or more enzyme(s) that consume one or more (6E)-8-hydroxygeraniol pathway precursors, said reduced activity being reduced relative to a control cell.
The engineered microbial cell of embodiment 13, wherein the one or more enzyme(s) that consume one or more (6E)-8-hydroxygeraniol pathway precursors comprise a bifunctional (2E,6E)-farnesyl diphosphate synthase/dimethylallyltranstransferase and/or a geranyl pyrophosphate synthase.
The engineered microbial cell of any one of embodiments 9-14, wherein the engineered microbial cell additionally includes means for expressing a feedback-deregulated HMG-CoA reductase.
The engineered microbial cell of any one of embodiments 9-15, wherein the engineered microbial cell includes means for increasing the availability of acetyl-CoA due to a higher rate of acetyl-CoA synthesis and/or a lower rate of acetyl-CoA degradation, relative to a control cell.
The engineered microbial cell of any one of embodiments 1-16, wherein the engineered microbial cell includes a fungal cell.
The engineered microbial cell of embodiment 17, wherein the engineered microbial cell includes a yeast cell.
The engineered microbial cell of embodiment 18, wherein the yeast cell is a cell of the genus Saccharomyces.
The engineered microbial cell of embodiment 19, wherein the yeast cell is a cell of the species cerevisiae.
The engineered microbial cell of embodiment 18, wherein the yeast cell is a cell of the genus Yarrowia.
The engineered microbial cell of embodiment 21, wherein the yeast cell is a cell of the species lipolytica.
The engineered microbial cell of any one of embodiments 1-22, wherein the non-native geraniol synthase includes a geraniol synthase having at least 70% amino acid sequence identity with a geraniol synthase from Perilla setoyensis.
The engineered microbial cell of any one of embodiments 1-22, wherein the non-native geraniol synthase includes a geraniol synthase having at least 70% amino acid sequence identity with a geraniol synthase from Vitis vinifera.
The engineered microbial cell of any one of embodiments 1-23, wherein the non-native geraniol-8-hydroxylase includes a geraniol-8-hydroxylase having at least 70% amino acid sequence identity with a geraniol-8-hydroxylase from Phaseolus angularis.
The engineered microbial cell of any one of embodiments 4 or 12-25, wherein the increased activity of the isopentenyl-diphosphate delta-isomerase is achieved by heterologously expressing a isopentenyl-diphosphate delta-isomerase.
The engineered microbial cell of embodiment 26, wherein the heterologous isopentenyl-diphosphate delta-isomerase includes an isopentenyl-diphosphate delta-isomerase having at least 70% amino acid sequence identity with an isopentenyl-diphosphate delta-isomerase from Saccharomyces cerevisiae.
The engineered microbial cell of any one of embodiments 6, and 14-27, wherein the one or more enzyme(s) that consume one or more (6E)-8-hydroxygeraniol pathway precursors comprise a bifunctional (2E,6E)-farnesyl diphosphate synthase/dimethylallyltranstransferase.
The engineered microbial cell of embodiment 28, wherein a bifunctional (2E,6E)-farnesyl diphosphate synthase/dimethylallyltranstransferase having at least 70% amino acid identity with a bifunctional (2E,6E)-farnesyl diphosphate synthase/dimethylallyltranstransferase from Escherichia coli and including amino acid substitution S80F.
The engineered microbial cell of any one of embodiments 7, or 15-27, wherein the HMG-CoA reductase is a variant of a S. cerevisiae HMG-CoA reductase.
The engineered microbial cell of any one of embodiments 1-30, wherein, when cultured, the engineered microbial cell produces (6E)-8-hydroxygeraniol at a level greater than 100 μg/L of culture medium.
A culture of engineered microbial cells according to any one of embodiments 1-31.
The culture of embodiment 32, wherein the substrate includes a carbon source and a nitrogen source selected from the group consisting of urea, an ammonium salt, ammonia, and any combination thereof.
The culture of any one of embodiments 32-33, wherein the engineered microbial cells are present in a concentration such that the culture has an optical density at 600 nm of 10-500.
The culture of any one of embodiments 32-34, wherein the culture includes (6E)-8-hydroxygeraniol.
The culture of any one of embodiments 32-35, wherein the culture includes (6E)-8-hydroxygeraniol at a level greater than 100 μg/L of culture medium.
A method of culturing engineered microbial cells according to any one of embodiments 1-31, the method including culturing the cells under conditions suitable for producing (6E)-8-hydroxygeraniol.
The method of embodiment 37, wherein the method includes fed-batch culture, with an initial glucose level in the range of 1-100 g/L, followed controlled sugar feeding.
The method of embodiment 37 or embodiment 38, wherein the fermentation substrate includes glucose and a nitrogen source selected from the group consisting of urea, an ammonium salt, ammonia, and any combination thereof.
The method of any one of embodiments 37-39, wherein the culture is pH-controlled during culturing.
The method of any one of embodiments 37-40, wherein the culture is aerated during culturing.
The method of any one of embodiments 37-41, wherein the engineered microbial cells produce (6E)-8-hydroxygeraniol at a level greater than 100 μg/L of culture medium.
The method of any one of embodiments 37-42, wherein the method additionally includes recovering (6E)-8-hydroxygeraniol from the culture.
A method for preparing (6E)-8-hydroxygeraniol using microbial cells engineered to produce (6E)-8-hydroxygeraniol, the method including: (a) expressing a non-native geranyl diphosphate diphosphatase (geraniol synthase) in microbial cells; (b) expressing a non-native geraniol-8-hydroxylase in the microbial cells; (c) cultivating the microbial cells in a suitable culture medium under conditions that permit the microbial cells to produce (6E)-8-hydroxygeraniol, wherein the (6E)-8-hydroxygeraniol is released into the culture medium; and (d) isolating (6E)-8-hydroxygeraniol from the culture medium.
Production of di-alcohol such as (6E)-8-hydroxygeraniol by biological fermentation can make a monomer economically accessible for old, as well as newly identified, materials applications. Di-alcohol containing polymers have attractive properties for novel material applications.
We conducted a search of metabolism [1] to identify enzymes that enable a metabolic pathway to produce (6E)-8-hydroxygeraniol in industrial host organisms (see Table 1). To engineer production of (6E)-8-hydroxygeraniol an industrial microorganism required genetic engineering tools and methods to manipulate DNA sequences (see
As noted above, (6E)-8-hydroxygeraniol is a monoterpene that is produced metabolically from the terpenoid pathway. There are two terpenoid biosynthesis pathways in microorganisms: the mevalonate pathway and the non-mevalonate pathway. Both Saccharomyces cerevisiae and Yarrowia lipolytica use the mevalonate pathway for production of terpenes [2].
The present disclosure describes the engineering of microbial cells for fermentative production of (6E)-8-hydroxygeraniol and provides novel engineered microbial cells and cultures, as well as related (6E)-8-hydroxygeraniol production methods.
Terms used in the claims and specification are defined as set forth below unless otherwise specified.
The term “fermentation” is used herein to refer to a process whereby a microbial cell converts one or more substrate(s) into a desired product (such as (6E)-8-hydroxygeraniol) by means of one or more biological conversion steps, without the need for any chemical conversion step.
The term “engineered” is used herein, with reference to a cell, to indicate that the cell contains at least one targeted genetic alteration introduced by man that distinguishes the engineered cell from the naturally occurring cell.
The term “native” is used herein to refer to a cellular component, such as a polynucleotide or polypeptide, that is naturally present in a particular cell. A native polynucleotide or polypeptide is endogenous to the cell.
When used with reference to a polynucleotide or polypeptide, the term “non-native” refers to a polynucleotide or polypeptide that is not naturally present in a particular cell.
When used with reference to the context in which a gene is expressed, the term “non-native” refers to a gene expressed in any context other than the genomic and cellular context in which it is naturally expressed. A gene expressed in a non-native manner may have the same nucleotide sequence as the corresponding gene in a host cell, but may be expressed from a vector or from an integration point in the genome that differs from the locus of the native gene.
The term “heterologous” is used herein to describe a polynucleotide or polypeptide introduced into a host cell. This term encompasses a polynucleotide or polypeptide, respectively, derived from a different organism, species, or strain than that of the host cell. In this case, the heterologous polynucleotide or polypeptide has a sequence that is different from any sequence(s) found in the same host cell. However, the term also encompasses a polynucleotide or polypeptide that has a sequence that is the same as a sequence found in the host cell, wherein the polynucleotide or polypeptide is present in a different context than the native sequence (e.g., a heterologous polynucleotide can be linked to a different promotor and inserted into a different genomic location than that of the native sequence). “Heterologous expression” thus encompasses expression of a sequence that is non-native to the host cell, as well as expression of a sequence that is native to the host cell in a non-native context.
As used with reference to polynucleotides or polypeptides, the term “wild-type” refers to any polynucleotide having a nucleotide sequence, or polypeptide having an amino acid, sequence present in a polynucleotide or polypeptide from a naturally occurring organism, regardless of the source of the molecule; i.e., the term “wild-type” refers to sequence characteristics, regardless of whether the molecule is purified from a natural source; expressed recombinantly, followed by purification; or synthesized. The term “wild-type” is also used to denote naturally occurring cells.
A “control cell” is a cell that is otherwise identical to an engineered cell being tested, including being of the same genus and species as the engineered cell, but lacks the specific genetic modification(s) being tested in the engineered cell.
Enzymes are identified herein by the reactions they catalyze and, unless otherwise indicated, refer to any polypeptide capable of catalyzing the identified reaction. Unless otherwise indicated, enzymes may be derived from any organism and may have a native or mutated amino acid sequence. As is well known, enzymes may have multiple functions and/or multiple names, sometimes depending on the source organism from which they derive. The enzyme names used herein encompass orthologs, including enzymes that may have one or more additional functions or a different name.
The term “feedback-deregulated” is used herein with reference to an enzyme that is normally negatively regulated by a downstream product of the enzymatic pathway (i.e., feedback-inhibition) in a particular cell. In this context, a “feedback-deregulated” enzyme is a form of the enzyme that is less sensitive to feedback-inhibition than the native enzyme native to the cell. A feedback-deregulated enzyme may be produced by introducing one or more mutations into a native enzyme. Alternatively, a feedback-deregulated enzyme may simply be a heterologous, native enzyme that, when introduced into a particular microbial cell, is not as sensitive to feedback-inhibition as the native, native enzyme. In some embodiments, the feedback-deregulated enzyme shows no feedback-inhibition in the microbial cell.
The term “(6E)-8-hydroxygeraniol” refers to (2E,6E)-2,6-Dimethyl-2,6-octadiene-1,8-diol (CAS#26488-97-1).
The term “sequence identity,” in the context of two or more amino acid or nucleotide sequences, refers to two or more sequences that are the same or have a specified percentage of amino acid residues or nucleotides that are the same, when compared and aligned for maximum correspondence, as measured using a sequence comparison algorithm or by visual inspection.
For sequence comparison to determine percent nucleotide or amino acid sequence identity, typically one sequence acts as a “reference sequence,” to which a “test” sequence is compared. When using a sequence comparison algorithm, test and reference sequences are input into a computer, subsequence coordinates are designated, if necessary, and sequence algorithm program parameters are designated. The sequence comparison algorithm then calculates the percent sequence identity for the test sequence relative to the reference sequence, based on the designated program parameters. Alignment of sequences for comparison can be conducted using BLAST set to default parameters.
The term “titer,” as used herein, refers to the mass of a product (e.g., (6E)-8-hydroxygeraniol) produced by a culture of microbial cells divided by the culture volume.
As used herein with respect to recovering (6E)-8-hydroxygeraniol from a cell culture, “recovering” refers to separating the (6E)-8-hydroxygeraniol from at least one other component of the cell culture medium.
Engineering Microbes for (6E)-8-hydroxygeraniol Production
(6E)-8-hydroxygeraniol Biosynthesis Pathway
(6E)-8-hydroxygeraniol is derived from the mevalonate biosynthesis pathway, based on the core metabolite precursor acetyl-CoA. This pathway is illustrated in
Engineering for Microbial (6E)-8-hydroxygeraniol Production
Any geraniol synthase and geraniol-8-hydroxylase that are active in the microbial cell being engineered may be introduced into the cell, typically by introducing and expressing the genes encoding the enzymes using standard genetic engineering techniques. Suitable geraniol synthases and geraniol-8-hydroxylases may be derived from any source, including plant, archaeal, fungal, gram-positive bacterial, and gram-negative bacterial sources. Exemplary sources include, but are not limited to: Perilla setoyensis, Phaseolus angularis, Vitis vinifera (grape), Swertia mussotii (Felwort), Populus trichocarpa (Western balsam poplar) (Populus balsamifera subsp. Trichocarpa), Papaver somniferum, Petroselinum crispum, Oryza sativa, Methanosphaerula palustris Methanocaldococcus jannaschii, Zygosaccharomyces bailii, Penicillium marneffei, Talaromyces stipitatus, Trichophyton equinum, Propionibacterium sp. oral, Enterococcus faecium, Streptomyces hygroscopicus, Streptomyces sviceus, Modestobacter marinus, Pseudomonas putida, Sinorhizobium fredii, Cathatanthus roseaus, Zea mays, Catharanthus roseus (Madagascar periwinkle) (Vinca rosea), Perilla frutescens var. crispa, Perilla frutescens var. hirtella, Cinnamomum tenuipile (Alseodaphne mollis), Ocimum basilicum (Sweet basil), Perilla citriodora, Olea europaea (Common olive), Phyla dulcis (Aztec sweet herb) (Lippia dulcis), Rosa rugosa (Rugosa rose), Camptotheca acuminata (Happy tree), Citrus jambhiri (Rough lemon), Picrorhiza kurrooa, Arabidopsis thaliana (Mouse-ear cress), Glycine max (Soybean) (Glycine hispida), Beta vulgaris (Sugar beet), Mollugo verticillata (Green carpetweed), Amborella trichopoda, Solanum tuberosum (Potato), Glycine soja (Wild soybean), Vanda coerulea, Oryza barthii, Hypericum androsaemum (Tutsan), Solanum lycopersicum (Tomato) (Lycopersicon esculentum), and Coffea canephora (Robusta coffee).
One or more copies of each of a geraniol synthase and a geraniol-8-hydroxylase gene can be introduced into a selected microbial host cell. If more than one copy of a gene is introduced, the copies can be copies can have the same or different nucleotide sequences. In some embodiments, one or both of the heterologous gene(s) is/are expressed from a strong, constitutive promoter. In some embodiments, the heterologous geraniol synthase and/or the heterologous geraniol-8-hydroxylase genes are expressed from inducible promoters. The heterologous genes can optionally be codon-optimized to enhance expression in the selected microbial host cell.
In Example 1, S. cerevisiae was engineered to express geraniol synthase from Perilla setoyensis (UniProt ID C0KWV4) (SEQ ID NO:5) and geraniol-8-hydroxylase from Phaseolus angularis (UniProt ID C6J436) (SEQ ID NO:11), which yielded a (6E)-8-hydroxygeraniol titer of 37.5 μg/L in a first round of genetic engineering (Table 1, below). This titer was increased in a second round to 122.9 μg/L in a strain that additionally expressed three copies of isopentenyl-diphosphate delta3-delta2-isomerase (UniProt ID P15496) (SEQ ID NO:25).
In Example 2, Y. lipolytica was engineered to express geraniol synthase Perilla setoyensis (UniProt ID C0KWV4) (SEQ ID NO:99), geraniol 8-hydroxylase from Phaseolus angularis (UniProt ID A0A0L9UT99) (SEQ ID NO:115), and isopentenyl-diphosphate delta3-delta2-isomerase from S. cerevisiae (UniProt ID P15496) (SEQ ID NO:126), which yielded a (6E)-8-hydroxygeraniol titer of 310 microgram/L.
In Example 3, S. cerevisiae was engineered to express geraniol synthase from Perilla setoyensis (UniProt ID C0KWV4) (SEQ ID NO:99), geraniol-8-hydroxylase from Phaseolus angularis (UniProt ID C6J436), and isopentenyl-diphosphate delta3-delta2-isomerase from S. cerevisiae (UniProt ID P15496) (SEQ ID NO:126), which yielded a (6E)-8-hydroxygeraniol titer of 217 microgram/L.
One approach to increasing (6E)-8-hydroxygeraniol production in a microbial cell that is capable of such production is to increase the activity of one or more upstream enzymes in the (6E)-8-hydroxygeraniol biosynthesis pathway. Upstream pathway enzymes include all enzymes involved in the conversions from a feedstock all the way to into the last native metabolite (i.e., geranyl diphosphate in S. cerevisiae). In certain embodiments, the upstream pathway enzymes refer specifically to the enzymes involved in the conversion of key precursors into geranyl diphosphate in the pathway leading to (6E)-8-hydroxygeraniol. Such genes include those encoding an ATP-citrate synthase, an acetyl-CoA synthetase, a thiolase, a hydroxymethylglutaryl coenzyme A synthase (HMG-CoA synthase), a hydroxymethylglutaryl coenzyme A reductase (HMG-CoA reductase), a mevalonate kinase, a phosphomevalonate kinase, a diphosphomevalonate decarboxylase, an isopentenyl-diphosphate delta-isomerase (systematic name: isopentenyl-diphosphate delta2-delta3-isomerase), and a geranyl diphosphate synthase. Suitable upstream pathway genes may be derived from any source, including, for example, those discussed above as sources for a heterologous geraniol synthase or geraniol-8-hydroxylase gene.
In some embodiments, the activity of one or more upstream pathway enzymes is increased by modulating the expression or activity of the native enzyme(s). Examples of this approach include: (1) over-expression of HMG-CoA reductase and/or constitutive over-expression of geranyl diphosphate synthase to increase the level of the (6E)-8-hydroxygeraniol pathway precursor geranyl diphosphate, and/or (2) over-expression of ATP-citrate synthase (P53396) and/or acetyl-CoA synthetase (ACS, Q8ZKF6) improve the availability of acetyl-CoA.
The expression of the native upstream pathway enzymes can be increased by means of one or more natural regulators of upstream pathway activity. For example, to improve expression of the isoprenoid pathway enzymes, one may introduce, and optionally, over-express, a variant of a sterol uptake control protein, UPC2 (UniProt ID Q12151, from Saccharomyces cerevisiae S288c, containing either G888D or G888R [these designations indicate amino acid substitutions, using the standard one-letter code for amino acids, with the first letter referring to the wild-type residue and the last letter referring to the replacement residue; the numbers indicate the position of the amino acid substitution in the translated protein]) [6, 7]. The sterol uptake control protein UPC2 regulates sterol synthesis and the C-terminal amino acid substitutions increase the activity of this transcription factor. For example, UPC2 binding element upstream of ERG8 enables UPC2 transcriptional activation of ERG8 in addition to other sterol biosynthesis pathway genes [7].
Alternatively, or in addition, one or more promoters can be substituted for native promoters using, for example, a technique such as that illustrated in
In some embodiments, the activity of one or more upstream pathway enzymes is supplemented by introducing one or more of the corresponding genes into the geraniol synthase- and geraniol-8-hydroxylase-expressing microbial host cell. Example 1 describes the successful engineering of a microbial host cell to express a heterologous geraniol synthase and a heterologous geraniol-8-hydroxylase, along with an introduced gene encoding an isopentenyl-diphosphate Delta-isomerase.
An introduced upstream pathway gene may be from an organism other than that of the host cell or may simply be an additional copy of a native gene. In some embodiments, one or more such genes are introduced into a microbial host cell capable of (6E)-8-hydroxygeraniol production and expressed from a strong constitutive promoter and/or can optionally be codon-optimized to enhance expression in the selected microbial host cell.
In various embodiments, the engineering of a (6E)-8-hydroxygeraniol-producing microbial cell to increase the activity of one or more upstream pathway enzymes increases the (6E)-8-hydroxygeraniol titer by at least 10, 20, 30, 40, 50, 60, 70, 80, or 90 percent or by at least 2-fold, 2.5-fold, 3-fold, 3.5-fold, 4-fold, 4.5-fold, 5-fold, 5.5-fold, 6-fold, 6.5-fold, 7-fold, 7.5-fold, 8-fold, 8.5-fold, 9-fold, 9.5-fold, 10-fold, 11-fold, 12-fold, 13-fold, 14-fold, 15-fold, 16-fold, 17-fold, 18-fold, 19-fold, 20-fold, 21-fold, 22-fold, 23-fold, 24-fold, 25-fold, 30-fold, 35-fold, 40-fold, 45-fold, 50-fold, 55-fold, 60-fold, 65-fold, 70-fold, 75-fold, 80-fold, 85-fold, 90-fold, 95-fold, or 100-fold. In various embodiments, the increase in (6E)-8-hydroxygeraniol titer is in the range of 10 percent to 100-fold, 2-fold to 50-fold, 5-fold to 40-fold, 10-fold to 30-fold, or any range bounded by any of the values listed above. (Ranges herein include their endpoints.) These increases are determined relative to the (6E)-8-hydroxygeraniol titer observed in a (6E)-8-hydroxygeraniol-producing microbial cell that lacks any increase in activity of upstream pathway enzymes. This reference cell may have one or more other genetic alterations aimed at increasing (6E)-8-hydroxygeraniol production, e.g., the cell may express a feedback-deregulated enzyme.
In various embodiments, the (6E)-8-hydroxygeraniol titers achieved by increasing the activity of one or more upstream pathway genes are at least 100, 200, 300, 400, 500, 600, 700, 800, or 900 μg/L, or at least 1, 10, 50, 75, 100, 200, 300, 400, 500, 600, 700, 800, or 900 mg/L or at least 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, or 10 gm/L. In various embodiments, the titer is in the range of 100 μg/L to 10 gm/L, 200 μg/L to 5 gm/L, 500 μg/L to 4 gm/L, 1 mg/L to 3 gm/L, 500 mg/L to 2 gm/L or any range bounded by any of the values listed above.
Since (6E)-8-hydroxygeraniol biosynthesis is subject to feedback inhibition, another approach to increasing (6E)-8-hydroxygeraniol production in a microbial cell engineered to produce (6E)-8-hydroxygeraniol is to introduce feedback-deregulated forms of one or more enzymes that are normally subject to feedback regulation. HMG-CoA reductase is one such enzyme. A feedback-deregulated form can be a heterologous, native enzyme that is less sensitive to feedback inhibition than the native enzyme in the particular microbial host cell. Alternatively, a feedback-deregulated form can be a variant of a native or heterologous enzyme that has one or more mutations or truncations rendering it less sensitive to feedback inhibition than the corresponding native enzyme. Examples of the latter include a variant HMG-CoA reductase (from S. cerevisiae) that has an N-terminal truncation (SEQ ID NO:27). Expression of this feedback-deregulated HMG-CoA reductase in a host cell has been shown to improve mevalonate pathway flux in S. cerevisiae [3] and other organisms (see, e.g., PCT Publication No. WO2001031027A1, describing genetic engineering of plants).
In various embodiments, the engineering of a (6E)-8-hydroxygeraniol-producing microbial cell to express a feedback-deregulated enzymes increases the (6E)-8-hydroxygeraniol titer by at least 10, 20, 30, 40, 50, 60, 70, 80, or 90 percent or by at least 2-fold, 2.5-fold, 3-fold, 3.5-fold, 4-fold, 4.5-fold, 5-fold, 5.5-fold, 6-fold, 6.5-fold, 7-fold, 7.5-fold, 8-fold, 8.5-fold, 9-fold, 9.5-fold, 10-fold, 11-fold, 12-fold, 13-fold, 14-fold, 15-fold, 16-fold, 17-fold, 18-fold, 19-fold, 20-fold, 21-fold, 22-fold, 23-fold, 24-fold, 25-fold, 30-fold, 35-fold, 40-fold, 45-fold, 50-fold, 55-fold, 60-fold, 65-fold, 70-fold, 75-fold, 80-fold, 85-fold, 90-fold, 95-fold, or 100-fold. In various embodiments, the increase in (6E)-8-hydroxygeraniol titer is in the range of 10 percent to 100-fold, 2-fold to 50-fold, 5-fold to 40-fold, 10-fold to 30-fold, or any range bounded by any of the values listed above. These increases are determined relative to the (6E)-8-hydroxygeraniol titer observed in a (6E)-8-hydroxygeraniol-producing microbial cell that does not express a feedback-deregulated enzyme. This reference cell may (but need not) have other genetic alterations aimed at increasing (6E)-8-hydroxygeraniol production, i.e., the cell may have increased activity of an upstream pathway enzyme resulting from some means other than feedback-insensitivity.
In various embodiments, the (6E)-8-hydroxygeraniol titers achieved by using a feedback-deregulated enzyme to increase flux though the (6E)-8-hydroxygeraniol biosynthetic pathway are at least 100, 200, 300, 400, 500, 600, 700, 800, or 900 μg/L, or at least 1, 10, 50, 75, 100, 200, 300, 400, 500, 600, 700, 800, or 900 mg/L or at least 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, or 10 g/L. In various embodiments, the titer is in the range of 100 μg/L to 10 g/L, 200 μg/L to 5 g/L, 500 μg/L to 4 g/L, 1 mg/L to 3 g/L, 500 mg/L to 2 g/L or any range bounded by any of the values listed above.
The approaches of supplementing the activity of one or more native enzymes and/or introducing one or more feedback-deregulated enzymes can be combined in geraniol synthase-expressing microbial cells to achieve even higher (6E)-8-hydroxygeraniol production levels.
Another approach to increasing (6E)-8-hydroxygeraniol production in a microbial cell that is capable of such production is to decrease the activity of one or more enzymes that shunt one or more precursors of (6E)-8-hydroxygeraniol biosynthesis into one or more side pathways (i.e., pathways leading to other products than (6E)-8-hydroxygeraniol). In some embodiments, the activity of one or more side-pathway enzymes is reduced by modulating the expression or activity of the native enzyme(s). Illustrative side-pathway enzymes include a bifunctional (2E,6E)-farnesyl diphosphate synthase/dimethylallyltranstransferase, a geranylgeranyl pyrophosphate synthase, and any side-pathway enzyme that consumes acetyl Co-A. The activity of such enzymes can be decreased, for example, by substituting the native promoter of the corresponding gene(s) with a less active or inactive promoter or by deleting the corresponding gene(s). See
The native bifunctional (2E,6E)-farnesyl diphosphate synthase/dimethylallyltranstransferase is bifunctional and can form geranyl diphosphate and subsequently a second reaction can convert geranyl diphosphate to (2E,6E)-farnesyl diphosphate. Because the native enzyme harbors these two activities and the intermediate is a (6E)-8-hydroxygeraniol pathway metabolite, it is beneficial to lower the expression of the native bifunctional (2E,6E)-farnesyl diphosphate synthase/dimethylallyltranstransferase. However, expression of the enzyme harboring the S80F amino acid substitution produces measurable quantities of the monoterpenoid [4] (see also U.S. Pat. No. 8,715,962). For example, to prevent additional flux to sterols, expression or activity of the bifunctional farnesyl-diphosphate farnesyltransferase (EC 2.5.1.21) encoded by ERGS in S. cerevisiae, and/or (2E,6E)-farnesyl diphosphate synthase (EC 2.5.1.10) encoded by ERG20 in S. cerevisiae are lowered to maximize geranyl diphosphate pools for (6E)-8-hydroxygeraniol biosynthesis.
In illustrative embodiments in S. cervisiae: (1) the promoter for the bifunctional (2E,6E)-farnesyl diphosphate synthase/dimethylallyltranstransferase (ERG20, YJL167W) can be replaced with the S. cerevisiae pRnr1 promoter to lower expression of this native enzyme which consumes the (6E)-8-hydroxygeneniol pathway metabolite geranyl diphosphate; (2) the promoter for the geranylgeranyl pyrophosphate synthase (Btsl, YPL069C) can be replaced with the S. cerevisiae pPsp2 to lower expression of this native enzyme which also consumes geranyl diphosphate; and/or one or more of the genes Pdc5 (YLR134W), Pdc6 (YGR087C), and Pdc1 (YLR044C) can be deleted to reduce acetyl-CoA consumption.
In various embodiments, the engineering of a (6E)-8-hydroxygeraniol-producing microbial cell to reduce precursor consumption by one or more side pathways increases the (6E)-8-hydroxygeraniol titer by at least 10, 20, 30, 40, 50, 60, 70, 80, or 90 percent or by at least 2-fold, 2.5-fold, 3-fold, 3.5-fold, 4-fold, 4.5-fold, 5-fold, 5.5-fold, 6-fold, 6.5-fold, 7-fold, 7.5-fold, 8-fold, 8.5-fold, 9-fold, 9.5-fold, 10-fold, 11-fold, 12-fold, 13-fold, 14-fold, 15-fold, 16-fold, 17-fold, 18-fold, 19-fold, 20-fold, 21-fold, 22-fold, 23-fold, 24-fold, 25-fold, 30-fold, 35-fold, 40-fold, 45-fold, 50-fold, 55-fold, 60-fold, 65-fold, 70-fold, 75-fold, 80-fold, 85-fold, 90-fold, 95-fold, or 100-fold. In various embodiments, the increase in (6E)-8-hydroxygeraniol titer is in the range of 10 percent to 100-fold, 2-fold to 50-fold, 5-fold to 40-fold, 10-fold to 30-fold, or any range bounded by any of the values listed above. These increases are determined relative to the (6E)-8-hydroxygeraniol titer observed in a (6E)-8-hydroxygeraniol-producing microbial cell that does not include genetic alterations to reduce precursor consumption. This reference cell may (but need not) have other genetic alterations aimed at increasing (6E)-8-hydroxygeraniol production, i.e., the cell may have increased activity of an upstream pathway enzyme.
In various embodiments, the (6E)-8-hydroxygeraniol titers achieved by reducing precursor consumption by one or more side pathways are at least 100, 200, 300, 400, 500, 600, 700, 800, or 900 μg/L, or at least 1, 10, 50, 75, 100, 200, 300, 400, 500, 600, 700, 800, or 900 mg/L or at least 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, or 10 g/L. In various embodiments, the titer is in the range of 100 μg/L to 10 g/L, 200 μg/L to 5 gm/L, 500 μg/L to 4 g/L, 1 mg/L to 3 g/L, 500 mg/L to 2 g/L or any range bounded by any of the values listed above.
The approaches of increasing the activity of one or more native enzymes and/or introducing one or more feedback-deregulated enzymes and/or reducing precursor consumption by one or more side pathways can be combined to achieve even higher (6E)-8-hydroxygeraniol production levels.
Microbial Host Cells
Any microbe that can be used to express introduced genes can be engineered for fermentative production of (6E)-8-hydroxygeraniol as described above. In certain embodiments, the microbe is one that is naturally incapable of fermentative production of (6E)-8-hydroxygeraniol. In some embodiments, the microbe is one that is readily cultured, such as, for example, a microbe known to be useful as a host cell in fermentative production of compounds of interest. Bacteria cells, including gram positive or gram negative bacteria can be engineered as described above. Examples include, in addition to C. glutamicum cells, Bacillus subtilus, B. licheniformis, B. lentus, B. brevis, B. stearothermophilus, B. alkalophilus, B. amyloliquefaciens, B. clausii, B. halodurans, B. megaterium, B. coagulans, B. circulans, B. lautus, B. thuringiensis, S. albus, S. lividans, S. coelicolor, S. griseus, Pseudomonas sp., P. alcaligenes, P. citrea, Lactobacilis spp. (such as L. lactis, L. plantarum), L. grayi, E. coli, E. faecium, E. gallinarum, E. casseliflavus, and/or E. faecalis cells.
There are numerous types of anaerobic cells that can be used as microbial host cells in the methods described herein. In some embodiments, the microbial cells are obligate anaerobic cells. Obligate anaerobes typically do not grow well, if at all, in conditions where oxygen is present. It is to be understood that a small amount of oxygen may be present, that is, there is some level of tolerance level that obligate anaerobes have for a low level of oxygen. Obligate anaerobes engineered as described above can be grown under substantially oxygen-free conditions, wherein the amount of oxygen present is not harmful to the growth, maintenance, and/or fermentation of the anaerobes.
Alternatively, the microbial host cells used in the methods described herein can be facultative anaerobic cells. Facultative anaerobes can generate cellular ATP by aerobic respiration (e.g., utilization of the TCA cycle) if oxygen is present. However, facultative anaerobes can also grow in the absence of oxygen. Facultative anaerobes engineered as described above can be grown under substantially oxygen-free conditions, wherein the amount of oxygen present is not harmful to the growth, maintenance, and/or fermentation of the anaerobes, or can be alternatively grown in the presence of greater amounts of oxygen.
In some embodiments, the microbial host cells used in the methods described herein are filamentous fungal cells. (See, e.g., Berka & Barnett, Biotechnology Advances, (1989), 7(2):127-154). Examples include Trichoderma longibrachiatum, T. viride, T. koningii, T. harzianum, Penicillium sp., Humicola insolens, H. lanuginose, H. grisea, Chrysosporium sp., C. lucknowense, Gliocladium sp., Aspergillus sp. (such as A. oryzae, A. niger, A. sojae, A. japonicus, A. nidulans, or A. awamori), Fusarium sp. (such as F. roseum, F. graminum F. cerealis, F. oxysporuim, or F. venenatum), Neurospora sp. (such as N. crassa or Hypocrea sp.), Mucor sp. (such as M. miehei), Rhizopus sp., and Emericella sp. cells. In particular embodiments, the fungal cell engineered as described above is A. nidulans, A. awamori, A. oryzae, A. aculeatus, A. niger, A. japonicus, T. reesei, T. viride, F. oxysporum, or F. solani. Illustrative plasmids or plasmid components for use with such hosts include those described in U.S. Patent Pub. No. 2011/0045563.
Yeasts can also be used as the microbial host cell in the methods described herein. Examples include: Saccharomyces sp., Schizosaccharomyces sp., Pichia sp., Hansenula polymorpha, Pichia stipites, Kluyveromyces marxianus, Kluyveromyces spp., Yarrowia lipolytica and Candida sp. In some embodiments, the Saccharomyces sp. is S. cerevisiae (See, e.g., Romanos et al., Yeast, (1992), 8(6):423-488). Illustrative plasmids or plasmid components for use with such hosts include those described in U.S. Pat. No. 7,659,097 and U.S. Patent Pub. No. 2011/0045563.
In some embodiments, the host cell can be an algal cell derived, e.g., from a green algae, red algae, a glaucophyte, a chlorarachniophyte, a euglenid, a chromista, or a dinoflagellate. (See, e.g., Saunders & Warmbrodt, “Gene Expression in Algae and Fungi, Including Yeast,” (1993), National Agricultural Library, Beltsville, Md.). Illustrative plasmids or plasmid components for use in algal cells include those described in U.S. Patent Pub. No. 2011/0045563.
In other embodiments, the host cell is a cyanobacterium, such as cyanobacterium classified into any of the following groups based on morphology: Chlorococcales, Pleurocapsales, Oscillatoriales, Nostocales, Synechosystic or Stigonematales (See, e.g., Lindberg et al., Metab. Eng., (2010) 12(1):70-79). Illustrative plasmids or plasmid components for use in cyanobacterial cells include those described in U.S. Patent Pub. Nos. 2010/0297749 and 2009/0282545 and in Intl. Pat. Pub. No. WO 2011/034863.
Genetic Engineering Methods
Microbial cells can be engineered for fermentative (6E)-8-hydroxygeraniol production using conventional techniques of molecular biology (including recombinant techniques), microbiology, cell biology, and biochemistry, which are within the skill of the art. Such techniques are explained fully in the literature, see e.g., “Molecular Cloning: A Laboratory Manual,” fourth edition (Sambrook et al., 2012); “Oligonucleotide Synthesis” (M. J. Gait, ed., 1984); “Culture of Animal Cells: A Manual of Basic Technique and Specialized Applications” (R. I. Freshney, ed., 6th Edition, 2010); “Methods in Enzymology” (Academic Press, Inc.); “Current Protocols in Molecular Biology” (F. M. Ausubel et al., eds., 1987, and periodic updates); “PCR: The Polymerase Chain Reaction,” (Mullis et al., eds., 1994); Singleton et al., Dictionary of Microbiology and Molecular Biology 2nd ed., J. Wiley & Sons (New York, N.Y. 1994).
Vectors are polynucleotide vehicles used to introduce genetic material into a cell. Vectors useful in the methods described herein can be linear or circular. Vectors can integrate into a target genome of a host cell or replicate independently in a host cell. For many applications, integrating vectors that produced stable transformants are preferred. Vectors can include, for example, an origin of replication, a multiple cloning site (MCS), and/or a selectable marker. An expression vector typically includes an expression cassette containing regulatory elements that facilitate expression of a polynucleotide sequence (often a coding sequence) in a particular host cell. Vectors include, but are not limited to, integrating vectors, prokaryotic plasmids, episomes, viral vectors, cosmids, and artificial chromosomes.
Illustrative regulatory elements that may be used in expression cassettes include promoters, enhancers, internal ribosomal entry sites (IRES), and other expression control elements (e.g., transcription termination signals, such as polyadenylation signals and poly-U sequences). Such regulatory elements are described, for example, in Goeddel, Gene Expression Technology: Methods In Enzymology 185, Academic Press, San Diego, Calif. (1990).
In some embodiments, vectors may be used to introduce systems that can carry out genome editing, such as CRISPR systems. See U.S. Patent Pub. No. 2014/0068797, published 6 Mar. 2014; see also Jinek M., et al., “A programmable dual-RNA-guided DNA endonuclease in adaptive bacterial immunity,” Science 337:816-21, 2012). In Type II CRISPR-Cas9 systems, Cas9 is a site-directed endonuclease, namely an enzyme that is, or can be, directed to cleave a polynucleotide at a particular target sequence using two distinct endonuclease domains (HNH and RuvC/RNase H-like domains). Cas9 can be engineered to cleave DNA at any desired site because Cas9 is directed to its cleavage site by RNA. Cas9 is therefore also described as an “RNA-guided nuclease.” More specifically, Cas9 becomes associated with one or more RNA molecules, which guide Cas9 to a specific polynucleotide target based on hybridization of at least a portion of the RNA molecule(s) to a specific sequence in the target polynucleotide. Ran, F. A., et al., (“In vivo genome editing using Staphylococcus aureus Cas9,” Nature 520(7546):186-91, 2015, Apr. 9], including all extended data) present the crRNA/tracrRNA sequences and secondary structures of eight Type II CRISPR-Cas9 systems. Cas9-like synthetic proteins are also known in the art (see U.S. Published Patent Application No. 2014-0315985, published 23 Oct. 2014).
Example 1 describes illustrative integration approaches for introducing polynucleotides and other genetic alterations into the genomes of S. cerevisiae cells.
Vectors or other polynucleotides can be introduced into microbial cells by any of a variety of standard methods, such as transformation, conjugation, electroporation, nuclear microinjection, transduction, transfection (e.g., lipofection mediated or DEAE-Dextrin mediated transfection or transfection using a recombinant phage virus), incubation with calcium phosphate DNA precipitate, high velocity bombardment with DNA-coated microprojectiles, and protoplast fusion. Transformants can be selected by any method known in the art. Suitable methods for selecting transformants are described in U.S. Patent Pub. Nos. 2009/0203102, 2010/0048964, and 2010/0003716, and International Publication Nos. WO 2009/076676, WO 2010/003007, and WO 2009/132220.
The above-described methods can be used to produce engineered microbial cells that produce, and in certain embodiments, overproduce, (6E)-8-hydroxygeraniol. Engineered microbial cells can have at least 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, or more genetic alterations, such as 30-40 alterations, as compared to a native microbial cell, such as any of the microbial host cells described herein. Engineered microbial cells described in the Example below have one, two, or three genetic alterations, but those of skill in the art can, following the guidance set forth herein, design microbial cells with additional alterations. In some embodiments, the engineered microbial cells have not more than 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, or 4 genetic alterations, as compared to a native microbial cell. In various embodiments, microbial cells engineered for (6E)-8-hydroxygeraniol production can have a number of genetic alterations falling within the any of the following illustrative ranges: 1-10, 1-9, 1-8, 2-7, 2-6, 2-5, 2-4, 2-3, 3-7, 3-6, 3-5, 3-4, etc.
In some embodiments, an engineered microbial cell expresses at least one heterologous geranyl diphosphate diphosphatase (geraniol synthase), such as in the case of a microbial host cell that does not naturally produce (6E)-8-hydroxygeraniol. In various embodiments, the microbial cell can include and express, for example: (1) a single heterologous geraniol synthase gene, (2) two or more heterologous geraniol synthase genes, which can be the same or different (in other words, multiple copies of the same heterologous geraniol synthase genes can be introduced or multiple, different heterologous geraniol synthase genes can be introduced), (3) a single heterologous geraniol synthase gene that is not native to the cell and one or more additional copies of an native geraniol synthase gene, or (4) two or more non-native geraniol synthase genes, which can be the same or different, and one or more additional copies of an native geraniol synthase gene.
In some embodiments, an engineered microbial cell expresses, at least one heterologous geraniol-8-hydroxylase, in addition to at least one heterologous geraniol synthase, such as in the case of a microbial host cell that does not have a geraniol-8-hydroxylase enzyme. In various embodiments, the microbial cell can include and express, for example: (1) a single heterologous geraniol-8-hydroxylase gene, (2) two or more heterologous geraniol-8-hydroxylase genes, which can be the same or different (in other words, multiple copies of the same heterologous geraniol-8-hydroxylase genes can be introduced or multiple, different heterologous geraniol-8-hydroxylase genes can be introduced), (3) a single heterologous geraniol-8-hydroxylase that is not native to the cell and one or more additional copies of an native geraniol-8-hydroxylase gene, or (4) two or more non-native geraniol-8-hydroxylase genes, which can be the same or different, and one or more additional copies of an native geraniol-8-hydroxylase.
This engineered host cell can include at least one additional genetic alteration that increases flux through the pathway leading to the production of geranyl-PP (the immediate precursor of (6E)-8-hydroxygeraniol). These “upstream” enzymes in the pathway include: an ATP-citrate synthase, an acetyl-CoA synthetase, a thiolase, a hydroxymethylglutaryl coenzyme A synthase (HMG-CoA synthase), a hydroxymethylglutaryl coenzyme A reductase (HMG-CoA reductase), a mevalonate kinase, a phosphomevalonate kinase, a diphosphomevalonate decarboxylase, an isopentenyl-diphosphate delta-isomerase, and a geranyl diphosphate synthase, including any isoforms, paralogs, or orthologs having these enzymatic activities (which as those of skill in the art readily appreciate may be known by different names). The at least one additional alteration can increase the activity of the upstream pathway enzyme(s) by any available means, e.g., by: (1) modulating the expression or activity of the native enzyme(s), (2) expressing one or more additional copies of the genes for the native enzymes, or (3) expressing one or more copies of the genes for one or more non-native enzymes.
In some embodiments, increased flux through the pathway can be achieved by expressing one or more genes encoding a feedback-deregulated enzyme, as discussed above. For example, the engineered host cell can include and express one or more feedback-deregulated HMG-CoA reductase genes.
The engineered microbial cells can contain introduced genes that have a native nucleotide sequence or that differ from native. For example, the native nucleotide sequence can be codon-optimized for expression in a particular host cell. The amino acid sequences encoded by any of these introduced genes can be native or can differ from native. In various embodiments, the amino acid sequences have at least 0 percent, 70 percent, 75 percent, 80 percent, 85 percent, 90 percent, 95 percent or 100 percent amino acid sequence identity with a native amino acid sequence.
In some embodiments, increased availability of precursors to (6E)-8-hydroxygeraniol can be achieved by reducing the expression or activity of one or more side-pathway enzymes, such as a bifunctional (2E,6E)-farnesyl diphosphate synthase/dimethylallyltranstransferase, a geranylgeranyl pyrophosphate synthase, and any side-pathway enzyme that consumes acetyl Co-A. For example, the engineered host cell can include one or more promoter swaps to down-regulate expression of any of these enzymes and/or can have their genes deleted to eliminate their expression entirely.
The approach described herein has been carried out in fungal cells, namely the yeast S. cerevisiae (a eukaryote), and in bacterial cells, namely C. glutamicum (a prokaryote). (See Example 1.)
Illustrative Engineered Fungal Cells
In certain embodiments, the engineered yeast (e.g., S. cerevisiae) cell expresses a heterologous geraniol synthase having at least 70 percent, 75 percent, 80 percent, 85 percent, 90 percent, 95 percent or 100 percent amino acid sequence identity to a geraniol synthase from Perilla setoyensis (e.g., SEQ ID NO:5). In particular embodiments, the Perilla setoyensis geraniol synthase can include SEQ ID NO:5.
The engineered yeast (e.g., S. cerevisiae) cell also expresses a heterologous geraniol-8-hydroxylase, which, in certain embodiments, has at least 70 percent, 75 percent, 80 percent, 85 percent, 90 percent, 95 percent or 100 percent amino acid sequence identity to a geraniol-8-hydroxylase from Phaseolus angularis (e.g., SEQ ID NO:11). In particular embodiments, the Phaseolus angularis geraniol-8-hydroxylase can include SEQ ID NO:11.
These may be the only genetic alterations of the engineered yeast cell, or the yeast cell can include one or more additional genetic alterations, as discussed more generally above.
An illustrative yeast (e.g., S. cerevisiae) cell with one or more additional genetic alterations can have increased activity of an upstream pathway enzyme, such as isopentenyl-diphosphate delta-isomerase, relative to the control cell, e.g., produced by introducing an additional copy of a native S. cereviseae isopentenyl-diphosphate delta-isomerase (SEQ ID NO:25) gene into the cell or a gene encoding an isopentenyl-diphosphate delta-isomerase having at least 70 percent, 75 percent, 80 percent, 85 percent, 90 percent, or 95 percent amino acid sequence identity to the native S. cereviseae isopentenyl-diphosphate delta-isomerase.
In particular embodiments, the engineered yeast (e.g., S. cerevisiae) cell additionally expresses a variant of a S. cerevisiae HMG-CoA reductase, which typically has at least 70 percent, 75 percent, 80 percent, 85 percent, 90 percent, or 95 percent amino acid sequence identity to the native S. cerevisiae HMG-CoA reductase or a truncated variant of the S. cerevisiae HMG-CoA reductase where amino acid residues 1-529 are deleted. In particular embodiments, the S. cerevisiae HMG-CoA reductase variant can include SEQ ID NO:27.
Any of the microbial cells described herein can be cultured, e.g., for maintenance, growth, and/or (6E)-8-hydroxygeraniol production.
In some embodiments, the cultures are grown to an optical density at 600 nm of 10-500, such as an optical density of 50-150.
In various embodiments, the cultures include produced (6E)-8-hydroxygeraniol at titers of at least 10, 25, 50, 75, 100, 200, 300, 400, 500, 600, 700, 800, or 900 μg/L, or at least 1, 10, 50, 75, 100, 200, 300, 400, 500, 600, 700, 800, or 900 mg/L or at least 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, or 10 gm/L. In various embodiments, the titer is in the range of 10 μg/L to 10 gm/L, 25 μg/L to 10 gm/L, 100 μg/L to 10 gm/L, 200 μg/L to 5 gm/L, 500 μg/L to 4 gm/L, 1 mg/L to 3 gm/L, 500 mg/L to 2 gm/L or any range bounded by any of the values listed above.
Culture Media
Microbial cells can be cultured in any suitable medium including, but not limited to, a minimal medium, i.e., one containing the minimum nutrients possible for cell growth. Minimal medium typically contains: (1) a carbon source for microbial growth; (2) salts, which may depend on the particular microbial cell and growing conditions; and (3) water. Suitable media can also include any combination of the following: a nitrogen source for growth and product formation, a sulfur source for growth, a phosphate source for growth, metal salts for growth, vitamins for growth, and other cofactors for growth.
Any suitable carbon source can be used to cultivate the host cells. The term “carbon source” refers to one or more carbon-containing compounds capable of being metabolized by a microbial cell. In various embodiments, the carbon source is a carbohydrate (such as a monosaccharide, a disaccharide, an oligosaccharide, or a polysaccharide), or an invert sugar (e.g., enzymatically treated sucrose syrup). Illustrative monosaccharides include glucose (dextrose), fructose (levulose), and galactose; illustrative oligosaccharides include dextran or glucan, and illustrative polysaccharides include starch and cellulose. Suitable sugars include C6 sugars (e.g., fructose, mannose, galactose, or glucose) and C5 sugars (e.g., xylose or arabinose). Other, less expensive carbon sources include sugar cane juice, beet juice, sorghum juice, and the like, any of which may, but need not be, fully or partially deionized.
The salts in a culture medium generally provide essential elements, such as magnesium, nitrogen, phosphorus, and sulfur to allow the cells to synthesize proteins and nucleic acids.
Minimal medium can be supplemented with one or more selective agents, such as antibiotics.
To produce (6E)-8-hydroxygeraniol, the culture medium can include, and/or is supplemented during culture with, glucose and/or a nitrogen source such as urea, an ammonium salt, ammonia, or any combination thereof.
Culture Conditions
Materials and methods suitable for the maintenance and growth of microbial cells are well known in the art. See, for example, U.S. Pub. Nos. 2009/0203102, 2010/0003716, and 2010/0048964, and International Pub. Nos. WO 2004/033646, WO 2009/076676, WO 2009/132220, and WO 2010/003007, Manual of Methods for General Bacteriology Gerhardt et al., eds), American Society for Microbiology, Washington, D.C. (1994) or Brock in Biotechnology: A Textbook of Industrial Microbiology, Second Edition (1989) Sinauer Associates, Inc., Sunderland, Mass.
In general, cells are grown and maintained at an appropriate temperature, gas mixture, and pH (such as about 20° C. to about 37° C., about 6% to about 84% CO2, and a pH between about 5 to about 9). In some aspects, cells are grown at 35° C. In certain embodiments, such as where thermophilic bacteria are used as the host cells, higher temperatures (e.g., 50° C.-75° C.) may be used. In some aspects, the pH ranges for fermentation are between about pH 5.0 to about pH 9.0 (such as about pH 6.0 to about pH 8.0 or about 6.5 to about 7.0). Cells can be grown under aerobic, anoxic, or anaerobic conditions based on the requirements of the particular cell.
Standard culture conditions and modes of fermentation, such as batch, fed-batch, or continuous fermentation that can be used are described in U.S. Publ. Nos. 2009/0203102, 2010/0003716, and 2010/0048964, and International Pub. Nos. WO 2009/076676, WO 2009/132220, and WO 2010/003007. Batch and Fed-Batch fermentations are common and well known in the art, and examples can be found in Brock, Biotechnology: A Textbook of Industrial Microbiology, Second Edition (1989) Sinauer Associates, Inc.
In some embodiments, the cells are cultured under limited sugar (e.g., glucose) conditions. In various embodiments, the amount of sugar that is added is less than or about 105% (such as about 100%, 90%, 80%, 70%, 60%, 50%, 40%, 30%, 20%, or 10%) of the amount of sugar that can be consumed by the cells. In particular embodiments, the amount of sugar that is added to the culture medium is approximately the same as the amount of sugar that is consumed by the cells during a specific period of time. In some embodiments, the rate of cell growth is controlled by limiting the amount of added sugar such that the cells grow at the rate that can be supported by the amount of sugar in the cell medium. In some embodiments, sugar does not accumulate during the time the cells are cultured. In various embodiments, the cells are cultured under limited sugar conditions for times greater than or about 1, 2, 3, 5, 10, 15, 20, 25, 30, 35, 40, 50, 60, or 70 hours or even up to about 5-10 days. In various embodiments, the cells are cultured under limited sugar conditions for greater than or about 5, 10, 15, 20, 25, 30, 35, 40, 50, 60, 70, 80, 90, 95, or 100% of the total length of time the cells are cultured. While not intending to be bound by any particular theory, it is believed that limited sugar conditions can allow more favorable regulation of the cells.
In some aspects, the cells are grown in batch culture. The cells can also be grown in fed-batch culture or in continuous culture. Additionally, the cells can be cultured in minimal medium, including, but not limited to, any of the minimal media described above. The minimal medium can be further supplemented with 1.0% (w/v) glucose (or any other six-carbon sugar) or less. Specifically, the minimal medium can be supplemented with 1% (w/v), 0.9% (w/v), 0.8% (w/v), 0.7% (w/v), 0.6% (w/v), 0.5% (w/v), 0.4% (w/v), 0.3% (w/v), 0.2% (w/v), or 0.1% (w/v) glucose. In some cultures, significantly higher levels of sugar (e.g., glucose) are used, e.g., at least 10% (w/v), 20% (w/v), 30% (w/v), 40% (w/v), 50% (w/v), 60% (w/v), 70% (w/v), or up to the solubility limit for the sugar in the medium. In some embodiments, the sugar levels falls within a range of any two of the above values, e.g.: 0.1-10% (w/v), 1.0-20% (w/v), 10-70% (w/v), 20-60% (w/v), or 30-50% (w/v). Furthermore, different sugar levels can be used for different phases of culturing. For fed-batch culture (e.g., of S. cerevisiae or C. glutamicum), the sugar level can be about 100-200 g/L (10-20% (w/v)) in the batch phase and then up to about 500-700 g/L (50-70% in the feed).
Additionally, the minimal medium can be supplemented 0.1% (w/v) or less yeast extract. Specifically, the minimal medium can be supplemented with 0.1% (w/v), 0.09% (w/v), 0.08% (w/v), 0.07% (w/v), 0.06% (w/v), 0.05% (w/v), 0.04% (w/v), 0.03% (w/v), 0.02% (w/v), or 0.01% (w/v) yeast extract. Alternatively, the minimal medium can be supplemented with 1% (w/v), 0.9% (w/v), 0.8% (w/v), 0.7% (w/v), 0.6% (w/v), 0.5% (w/v), 0.4% (w/v), 0.3% (w/v), 0.2% (w/v), or 0.1% (w/v) glucose and with 0.1% (w/v), 0.09% (w/v), 0.08% (w/v), 0.07% (w/v), 0.06% (w/v), 0.05% (w/v), 0.04% (w/v), 0.03% (w/v), or 0.02% (w/v) yeast extract. In some cultures, significantly higher levels of yeast extract can be used, e.g., at least 1.5% (w/v), 2.0% (w/v), 2.5% (w/v), or 3% (w/v). In some cultures (e.g., of S. cerevisiae or C. glutamicum), the yeast extract level falls within a range of any two of the above values, e.g.: 0.5-3.0% (w/v), 1.0-2.5% (w/v), or 1.5-2.0% (w/v).
Illustrative materials and methods suitable for the maintenance and growth of the engineered microbial cells described herein can be found below in Example 1.
(6E)-8-hydroxygeraniol Production and Recovery
Any of the methods described herein may further include a step of recovering (6E)-8-hydroxygeraniol. In some embodiments, the produced (6E)-8-hydroxygeraniol contained in a so-called harvest stream is recovered/harvested from the production vessel. The harvest stream may include, for instance, cell-free or cell-containing aqueous solution coming from the production vessel, which contains (6E)-8-hydroxygeraniol as a result of the conversion of production substrate by the resting cells in the production vessel. Cells still present in the harvest stream may be separated from the (6E)-8-hydroxygeraniol by any operations known in the art, such as for instance filtration, centrifugation, decantation, membrane crossflow ultrafiltration or microfiltration, tangential flow ultrafiltration or microfiltration or dead end filtration. After this cell separation operation, the harvest stream is essentially free of cells.
Further steps of separation and/or purification of the produced (6E)-8-hydroxygeraniol from other components contained in the harvest stream, i.e., so-called downstream processing steps may optionally be carried out. These steps may include any means known to a skilled person, such as, for instance, concentration, extraction, crystallization, precipitation, adsorption, ion exchange, and/or chromatography. Any of these procedures can be used alone or in combination to purify (6E)-8-hydroxygeraniol. Further purification steps can include one or more of, e.g., concentration, crystallization, precipitation, washing and drying, treatment with activated carbon, ion exchange, nanofiltration, and/or re-crystallization. The design of a suitable purification protocol may depend on the cells, the culture medium, the size of the culture, the production vessel, etc. and is within the level of skill in the art.
The following example is given for the purpose of illustrating various embodiments of the disclosure and is not meant to limit the present disclosure in any fashion. Changes therein and other uses which are encompassed within the spirit of the disclosure, as defined by the scope of the claims, will be identifiable to those skilled in the art.
Plasmid/DNA Design
All strains tested for this work were transformed with plasmid DNA designed using proprietary software. Plasmid designs were specific to one of the two host organisms engineered in this work. The plasmid DNA was physically constructed by a standard DNA assembly method. This plasmid DNA was then used to integrate metabolic pathway inserts by one of two host-specific methods, each described below.
S. cerevisiae Pathway Integration
A “split-marker, double-crossover” genomic integration strategy has been developed to engineer S. cerevisiae strains.
Cell Culture
The workflow established for S. cerevisiae involved a hit-picking step that consolidated successfully built strains using an automated workflow that randomized strains across the plate. For each strain that was successfully built, up to four replicates were tested from distinct colonies to test colony-to-colony variation and other process variation. If fewer than four colonies were obtained, the existing colonies were replicated so that at least four wells were tested from each desired genotype.
The colonies were consolidated into 96-well plates with selective medium (SD-ura for S. cerevisiae) and cultivated for two days until saturation and then frozen with 16.6% glycerol at −80° C. for storage. The frozen glycerol stocks were then used to inoculate a seed stage in minimal media with a low level of amino acids to help with growth and recovery from freezing. The seed plates were grown at 30° C. for 1-2 days. The seed plates were then used to inoculate a main cultivation plate with minimal medium and grown for 48-88 hours. Plates were removed at the desired time points and tested for cell density (OD600), viability and glucose, supernatant samples stored for LC-MS analysis for product of interest.
Cell Density
Cell density was measured using a spectrophotometric assay detecting absorbance of each well at 600 nm. Robotics were used to transfer fixed amounts of culture from each cultivation plate into an assay plate, followed by mixing with 175 mM sodium phosphate (pH 7.0) to generate a 10-fold dilution. The assay plates were measured using a Tecan M1000 spectrophotometer and assay data uploaded to a LIMS database. A non-inoculated control was used to subtract background absorbance. Cell growth was monitored by inoculating multiple plates at each stage, and then sacrificing an entire plate at each time point.
To minimize settling of cells while handling large number of plates (which could result in a non-representative sample during measurement) each plate was shaken for 10-15 seconds before each read. Wide variations in cell density within a plate may also lead to absorbance measurements outside of the linear range of detection, resulting in underestimate of higher OD cultures. In general, the tested strains so far have not varied significantly enough for this be a concern.
Liquid-Solid Separation
To harvest extracellular samples for analysis by LC-MS, liquid and solid phases were separated via centrifugation. Cultivation plates were centrifuged at 2000 rpm for 4 minutes, and the supernatant was transferred to destination plates using robotics. 75 μL of supernatant was transferred to each plate, with one stored at 4° C., and the second stored at 80° C. for long-term storage.
First Round Genetic Engineering Results
A first round of genetic engineering and screening was carried out using S. cerevisiae as host cells. A library approach was taken to identify functional enzymes in the host organism. A broad search of geraniol synthase sequences identified in total 13 orthologous sequences. A heterologous geraniol synthase was expressed in the host cells, in some cases, along with a heterologous geraniol-8-hydroxylase. In some cases, the geraniol synthase and/or geraniol-8-hydroxylase nucleotide sequences were codon-optimized for S. cerevisiae. The strains were produced and cultured as described above, and the (6E)-8-hydroxygeraniol titer in the culture media was measured by LC-MS. The strains and results are shown in Table 1 and in
Vitis vinifera
Swertia
mussotii
Vitis vinifera
Populus
trichocarpa
balsamifera
trichocarpa)
Perilla
Phaseolus
setoyensis
angularis
angularis)
Second Round Genetic Engineering Results
The best-performing first-round strain was used at the starting host for a second round of genetic engineering using a combinatorial library approach. In this round, an additional copy of 1-3 upstream pathway genes were introduced into separate “daughter” strains, under the control of a strong, constitutive promoters (Table 2). Upstream pathway genes represent all genes involved in the conversion of key precursors (e.g., acetyl-CoA) into the last native metabolite in the pathway leading to (6E)-8-hydroxygeraniol. Enzymes selected to be tested in strains in the combinatorial library approach are shown in the mevalonate pathway diagram (
Saccharomyces cerevisiae
Saccharomyces
cerevisiae
Saccharomyces
cerevisiae
Saccharomyces
cerevisiae
Saccharomyces
cerevisiae
Saccharomyces
Saccharomyces
cerevisiae
cerevisiae
Saccharomyces
Saccharomyces
cerevisiae
cerevisiae
Saccharomyces
cerevisiae
Saccharomyces
Saccharomyces
cerevisiae
cerevisiae
Saccharomyces
Saccharomyces
cerevisiae
cerevisiae
Saccharomyces
Saccharomyces
cerevisiae
cerevisiae
Saccharomyces
Saccharomyces
cerevisiae
cerevisiae
Saccharomyces
cerevisiae
Saccharomyces
cerevisiae
Saccharomyces cerevisiae
Saccharomyces
cerevisiae
Saccharomyces
cerevisiae
Saccharomyces
cerevisiae
Saccharomyces
cerevisiae
Saccharomyces
cerevisiae
Saccharomyces
cerevisiae
In addition to the enzymes above, the Table 2 strains also contained the best enzymes from first DBTAL round: the Saccharomyces cerevisiae host contains geraniol synthase (UniProt ID C0KWV4) and geraniol 8-hydroxylase (UniProt ID A0A0L9UT99). All enzymes tested in the second round have modified codon usage for Saccharomyces cerevisiae and Corynebacteria glutamicum.
Third and Fourth Round Genetic Engineering Results
A third round of genetic engineering produced no improved strains, most likely due to an error in strain construction. Fourth (Improvement) round strain designs and results are shown in Table 3.
S. cerevisiae
S. cerevisiae
S. cerevisiae
S. cerevisiae
S. cerevisiae
Staphylo-
coccus aureus
Candidatus
Halobonum
tyrrellensis
Cucumis
sativus
Lokiarchaeum
Cricetulus
griseus
Pyrodictium
occultum
S. cerevisiae
Abies grandis
Picea abies
Solanum
lycopersicum
Catharanthus
roseus
C. glutamicum
Bacillus subtilis
S. cerevisiae
S. cerevisiae
S. cerevisiae
S. cerevisiae
S. cerevisiae
S. cerevisiae
S. cerevisiae
S. cerevisiae
S. cerevisiae
S. cerevisiae
S. cerevisiae
S. cerevisiae
S. cerevisiae
S. cerevisiae
S. cerevisiae
S. cerevisiae
S. cerevisiae
S. cerevisiae
S. cerevisiae
S. cerevisiae
Yarrowia
lipolytica CLIB
Salmonella
typhimurium
S. cerevisiae
Salmonella
S. cerevisiae
typhimurium
Salmonella
S. cerevisiae
typhimurium
S. cerevisiae
S. cerevisiae
S. cerevisiae
S. cerevisiae
S. cerevisiae
S. cerevisiae
S. cerevisiae
E. coli (strain
Yarrowia
Emericella
lipolytica CLIB
nidulans ATCC
E. coli (strain
E. coli (strain
E. coli ATCC
E. coli (strain
E. coli (strain
E. coli ATCC
Yarrowia lipolytica was engineered using the approached described above for S. cerevisiae. The strains constructed in the first round of genetic engineering and their (6E)-8-hydroxygeranial titers are shown in Table 4.
Y.
lipolytica
E. coli
B.
subtillus
E. coli
E. coli
S.
cerevisiae
E. coli
Y.
lipolytica
E. coli
B.
subtillus
E. coli
E. coli
S.
cerevisiae
E. coli
Y.
lipolytica
E. coli
B.
subtillus
E. coli
S.
cerevisiae
E. coli
Y.
lipolytica
S.
B.
cerevisiae
subtillus
S.
S.
cerevisiae
cerevisiae
S.
Y.
cerevisiae
lipolytica
S.
B.
cerevisiae
subtillus
S.
S.
cerevisiae
cerevisiae
S.
Y.
cerevisiae
lipolytica
S.
B.
cerevisiae
subtillus
S.
S.
cerevisiae
cerevisiae
S.
Y.
cerevisiae
lipolytica
Perilla
setoyensis
Y.
lipolytica
Perilla
B.
Phaseolus
B.
setoyensis
subtillus
angularis
subtillus
Perilla
Phaseolus
setoyensis
angularis
Perilla
S.
Phaseolus
S.
setoyensis
cerevisiae
angularis
cerevisiae
Perilla
Y.
Phaseolus
Y.
setoyensis
lipolytica
angularis
lipolytica
Vitis
B.
Phaseolus
B.
vinifera
subtillus
angularis
subtillus
Vitis
Phaseolus
vinifera
angularis
Vitis
S.
Phaseolus
S.
vinifera
cerevisiae
angularis
cerevisiae
Vitis
Y.
Phaseolus
Y.
vinifera
lipolytica
angularis
lipolytica
Perilla
B.
Swertia
B.
setoyensis
subtillus
mussotii
subtillus
Perilla
S.
Swertia
S.
setoyensis
cerevisiae
mussotii
cerevisiae
Perilla
Y.
Swertia
Y.
setoyensis
lipolytica
mussotii
lipolytica
Perilla
B.
Phaseolus
B.
setoyensis
subtillus
angularis
subtillus
Perilla
S.
Phaseolus
S.
setoyensis
cerevisiae
angularis
cerevisiae
Perilla
Y.
Phaseolus
Y.
setoyensis
lipolytica
angularis
lipolytica
Vitis
B.
Phaseolus
B.
vinifera
subtillus
angularis
subtillus
Vitis
S.
Phaseolus
S.
vinifera
cerevisiae
angularis
cerevisiae
Vitis
Y.
Phaseolus
Y.
vinifera
lipolytica
angularis
lipolytica
Perilla
B.
Swertia
B.
setoyensis
subtillus
mussotii
subtillus
Perilla
S.
Swertia
S.
setoyensis
cerevisiae
mussotii
cerevisiae
Perilla
Y.
Swertia
Y.
setoyensis
lipolytica
mussotii
lipolytica
Phaseolus
S. cerevisiae
angularis
The best-performing enzymes were tested in four hosts: Yarrowia lipolytica, Bacillus subtillus, Corynebacteria glutamicum, Saccharomyces cerevisiae. The results for S. cerevisiae are shown in Table 5, below.
The best performing strain in Y. lipolytica produced a titer of 310 microgram/L. This Y. lipolytica strain expressed geraniol synthase (UniProt ID C0KWV4) from Perilla setoyensis, geraniol 8-hydroxylase (UniProt ID A0A0L9UT99) from Phaseolus angularis and isopentenyl-diphosphate delta3-delta2-isomerase (UniProt ID P15496) from S. cerevisiae. The second-best performing Y. lipolytica strain produced 200 microgram/L, and this strain expressed farnesyl diphosphate synthase (UniProt ID P22939) from Escherichia coli K12 harboring amino acid substitution S80F [4], geraniol synthase (UniProt ID E5GAH8) from Vitis vinifera, and geraniol 8-hydroxylase (UniProt ID A0A0L9UT99) from Phaseolus angularis.
The best performing strain in S. cerevisiae produced a titer of 217 microgram/L. This S. cerevisiae strain expressed geraniol synthase (UniProt ID C0KWV4) from Perilla setoyensis, geraniol 8-hydroxylase (UniProt ID A0A0L9UT99) from Phaseolus angularis and isopentenyl-diphosphate delta3-delta2-isomerase (UniProt ID P15496) from S. cerevisiae).
There was no titer produced by either B. subtillus or C. glutamicum strains.
S. cerevisiae
E. coli
B.
Perilla
subtillus
setoyensis
E. coli
S.
Perilla
cerevisiae
setoyensis
E. coli
Y.
Perilla
lipolytica
setoyensis
E. coli
B.
Vitis
subtillus
vinifera
E. coli
S.
Vitis
cerevisiae
vinifera
E. coli
Y.
Vitis
lipolytica
vinifera
E. coli
B.
Perilla
subtillus
setoyensis
E. coli
Perilla
setoyensis
E. coli
S.
Perilla
cerevisiae
setoyensis
E. coli
Y.
Perilla
lipolytica
setoyensis
S.
B.
Perilla
cerevisiae
subtillus
setoyensis
S.
Y.
Perilla
cerevisiae
lipolytica
setoyensis
S.
B.
Vitis
cerevisiae
subtillus
vinifera
S.
S.
Vitis
cerevisiae
cerevisiae
vinifera
S.
Y.
Vitis
cerevisiae
lipolytica
vinifera
S.
S.
Perilla
cerevisiae
cerevisiae
setoyensis
S.
Y.
Perilla
cerevisiae
lipolytica
setoyensis
Perilla
Phaseolus
setoyensis
angularis
S. cerevisiae
B.
Phaseolus
B.
subtillus
angularis
subtillus
S.
Phaseolus
S.
cerevisiae
angularis
cerevisiae
Y.
Phaseolus
Y.
lipolytica
angularis
lipolytica
B.
Phaseolus
B.
subtillus
angularis
subtillus
S.
Phaseolus
S.
cerevisiae
angularis
cerevisiae
Y.
Phaseolus
Y.
lipolytica
angularis
lipolytica
B.
Swertia
B.
subtillus
mussotii
subtillus
Swertia
mussotii
S.
Swertia
S.
cerevisiae
mussotii
cerevisiae
Y.
Swertia
Y.
lipolytica
mussotii
lipolytica
B.
Phaseolus
B.
subtillus
angularis
subtillus
Y.
Phaseolus
Y.
lipolytica
angularis
lipolytica
B.
Phaseolus
B.
subtillus
angularis
subtillus
S.
Phaseolus
S.
cerevisiae
angularis
cerevisiae
Y.
Phaseolus
Y.
lipolytica
angularis
lipolytica
S.
Swertia
S.
cerevisiae
mussotii
cerevisiae
Y.
Swertia
Y.
lipolytica
mussotii
lipolytica
S. cerevisiae
This application is a continuation application of international application no. PCT/US2018/64351, filed Dec. 6, 2018, which claims the benefit of U.S. provisional application No. 62/596,013, filed Dec. 7, 2017, both of which are hereby incorporated by reference in their entireties.
This invention was made with Government support under Agreement No. HR0011-15-9-0014, awarded by DARPA. The Government has certain rights in the invention.
| Number | Date | Country | |
|---|---|---|---|
| 62596013 | Dec 2017 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/US18/64351 | Dec 2018 | US |
| Child | 16450780 | US |
