Patent Application
20220112478
This application contains a Sequence Listing in computer readable form, which is incorporated herein by reference.
The present invention relates to means and methods for optimizing expression of a heterologous polypeptide of interest in Gram-positive host cells by co-expression with a foldase that is cognate to the heterologous polypeptide of interest.
Within industrial biotechnology, there is a continuous need for improving production yield and thereby process profitability in the production of enzymes and other industrially relevant proteins. A successful strategy has been to employ production host cells that over-express the gene encoding the target protein, e.g., by using multicopy strains containing several gene copies or enhancing the activity of the gene by modifying its control sequences. To fully leverage the beneficial effects of gene over-expression, it would be desirable to increase the secretory capacity of the production host cell in order to overcome any bottlenecks in the secretory machinery.
Foldases are proteins that assist in folding of other proteins. Over-expression of foldases in a production host cell may provide an enhanced folding of a given protein of interest, which in turn is likely to result in enhanced secretion of correctly folded protein of interest and thereby an improved production yield.
PrsA is an extracytoplasmic foldase identified in various Gram-positive bacteria, including the industrially relevant Bacillus licheniformis. PrsA exists as a dimeric lipoprotein anchored in the outer leaflet of the cell membrane, where it aids folding of proteins secreted via the conserved SecA-YEG pathway.
Co-expression with PrsA was shown to improve expression of polypeptides in Gram-positive host cells (WO 1994/019471).
The present invention is based on the surprising and inventive finding that cultivation of Gram-positive host cells co-expressing a heterologous polypeptide of interest with a foldase that is cognate to the heterologous polypeptide of interest provides on par or improved expression of the heterologous polypeptide of interest as well as on par or reduced secretion stress when compared to co-expression of the same heterologous polypeptide of interest with a non-cognate foldase.
In a first aspect, the present invention relates to a nucleic acid construct comprising:
a) a first heterologous promoter operably linked to at least one polynucleotide encoding a foldase; and
b) a second heterologous promotor operably linked to at least one polynucleotide encoding a polypeptide of interest;
wherein the foldase and the polypeptide of interest are from the same Gram-positive species.
In a second aspect, the present invention relates to an expression vector comprising a nucleic acid construct of the first aspect.
In a third aspect, the present invention relates to a Gram-positive host cell comprising in its genome a nucleic acid construct according to the first aspect and/or an expression vector according to the second aspect.
In a fourth aspect, the present invention relates to a method for producing a polypeptide of interest, the method comprising:
a) providing a Gram-positive host cell of the third aspect;
b) cultivating said host cell under conditions conducive for expression of the foldase and the polypeptide of interest; and, optionally
c) recovering the polypeptide of interest.
Foldase: The term “foldase” means an enzyme having foldase activity. Foldases are proteins that facilitate folding of polypeptides into a functional three-dimensional structure, and/or prevent aggregation of unfolded polypeptides into non-functional structures and any subsequent proteolytic degradation. PrsA is an example of a foldase in Gram-positive bacteria. PrsA is a dimer consisting of two monomers that forms two domains; a peptidylprolyl isomerase (PPlase, E.C. 5.2.1.8) domain that interconverts the cis and trans isomers of peptidyl-prolyl bonds, and a chaperone domain that assists polypeptide folding (Jakob et al., 2015, J. Biol. Chem. 290(6): 3278-3292). In Bacillus licheniformis PrsA monomers, the PPlase domain consists of amino acids 115 to 205 of SEQ ID NO: 9, and the chaperone domain consists of amino acids 1 to 114 and 206 of 267 of SEQ ID NO: 9. A crystal structure of PrsA from B. subtilis is provided in Jakob et al., supra.
Allelic variant: The term “allelic variant” means any of two or more alternative forms of a gene occupying the same chromosomal locus. Allelic variation arises naturally through mutation, and may result in polymorphism within populations. Gene mutations can be silent (no change in the encoded polypeptide) or may encode polypeptides having altered amino acid sequences. An allelic variant of a polypeptide is a polypeptide encoded by an allelic variant of a gene.
cDNA: The term “cDNA” means a DNA molecule that can be prepared by reverse transcription from a mature, spliced, mRNA molecule obtained from a eukaryotic or prokaryotic cell. cDNA lacks intron sequences that may be present in the corresponding genomic DNA. The initial, primary RNA transcript is a precursor to mRNA that is processed through a series of steps, including splicing, before appearing as mature spliced mRNA.
Coding sequence: The term “coding sequence” means a polynucleotide, which directly specifies the amino acid sequence of a polypeptide. The boundaries of the coding sequence are generally determined by an open reading frame, which begins with a start codon such as ATG, GTG, or TTG and ends with a stop codon such as TAA, TAG, or TGA. The coding sequence may be a genomic DNA, cDNA, synthetic DNA, or a combination thereof.
Cognate: The term “cognate” means from the same species.
Control sequences: The term “control sequences” means nucleic acid sequences necessary for expression of a polynucleotide encoding a mature polypeptide of the present invention. Each control sequence may be native (i.e., from the same gene) or foreign (i.e., from a different gene) to the polynucleotide encoding the polypeptide or native or foreign to each other. Such control sequences include, but are not limited to, a leader, polyadenylation sequence, propeptide sequence, promoter, signal peptide sequence, and transcription terminator. At a minimum, the control sequences include a promoter, and transcriptional and translational stop signals. The control sequences may be provided with linkers for the purpose of introducing specific restriction sites facilitating ligation of the control sequences with the coding region of the polynucleotide encoding a polypeptide.
Expression: The term “expression” includes any step involved in the production of a polypeptide including, but not limited to, transcription, post-transcriptional modification, translation, post-translational modification, and secretion.
Expression vector: The term “expression vector” means a linear or circular DNA molecule that comprises a polynucleotide encoding a polypeptide and is operably linked to control sequences that provide for its expression.
Heterologous: The term “heterologous” means foreign, i.e., from a different gene or from a different organism.
In the context of the present invention, the term “heterologous polypeptide of interest” means a polypeptide of interest that is foreign (i.e., from a different species) to the host cell expressing the polypeptide of interest.
In the context of the present invention, the term “heterologous promoter” means a promoter that is foreign (i.e., from a different gene) to the polynucleotide to which it is operably linked.
In the context of the present invention, the term “heterologous to the Gram-positive host cell” means foreign (i.e., from a different species) to the Gram-positive host cell.
Host cell: The term “host cell” means any cell type that is susceptible to transformation, transfection, transduction, or the like with a nucleic acid construct or expression vector comprising a polynucleotide of the present invention. The term “host cell” encompasses any progeny of a parent cell that is not identical to the parent cell due to mutations that occur during replication.
Isolated: The term “isolated” means a substance in a form or environment that does not occur in nature.
Mature polypeptide: The term “mature polypeptide” means a polypeptide in its final form following translation and any post-translational modifications, such as N-terminal processing, C-terminal truncation, glycosylation, phosphorylation, etc. It is known in the art that a host cell may produce a mixture of two of more different mature polypeptides (i.e., with a different C-terminal and/or N-terminal amino acid) expressed by the same polynucleotide. It is also known in the art that different host cells process polypeptides differently, and thus, one host cell expressing a polynucleotide may produce a different mature polypeptide (e.g., having a different C-terminal and/or N-terminal amino acid) as compared to another host cell expressing the same polynucleotide.
Nucleic acid construct: The term “nucleic acid construct” means a nucleic acid molecule, either single- or double-stranded, which is isolated from a naturally occurring gene or is modified to contain segments of nucleic acids in a manner that would not otherwise exist in nature or which is synthetic, which comprises one or more control sequences.
Operably linked: The term “operably linked” means a configuration in which a control sequence is placed at an appropriate position relative to the coding sequence of a polynucleotide such that the control sequence directs expression of the coding sequence.
Secretion stress: The term “secretion stress” means the stress experienced by a Gram-positive host cell upon co-expression of a heterologous polypeptide of interest with a foldase that is cognate to the heterologous polypeptide of interest. Secretion stress may be determined by the activity of the secretion stress-inducible promoter HtrA (PHtrA) as described in Examples 5-7 below. A reduction in secretion stress may be determined relative to the secretion stress experienced by a Gram-positive host cell of the same species co-expressing the heterologous polypeptide of interest with a foldase that is non-cognate to the heterologous polypeptide of interest.
Sequence identity: The relatedness between two amino acid sequences or between two nucleotide sequences is described by the parameter “sequence identity”.
For purposes of the present invention, the sequence identity between two amino acid sequences is determined using the Needleman-Wunsch algorithm (Needleman and Wunsch, 1970, J. Mol. Biol. 48: 443-453) as implemented in the Needle program of the EMBOSS package (EMBOSS: The European Molecular Biology Open Software Suite, Rice et al., 2000, Trends Genet. 16: 276-277), preferably version 5.0.0 or later. The parameters used are gap open penalty of 10, gap extension penalty of 0.5, and the EBLOSUM62 (EMBOSS version of BLOSUM62) substitution matrix. The output of Needle labeled “longest identity” (obtained using the -nobrief option) is used as the percent identity and is calculated as follows:
(Identical Residues×100)/(Length of Alignment−Total Number of Gaps in Alignment)
For purposes of the present invention, the sequence identity between two deoxyribonucleotide sequences is determined using the Needleman-Wunsch algorithm (Needleman and Wunsch, 1970, supra) as implemented in the Needle program of the EMBOSS package (EMBOSS: The European Molecular Biology Open Software Suite, Rice et al., 2000, supra), preferably version 5.0.0 or later. The parameters used are gap open penalty of 10, gap extension penalty of 0.5, and the EDNAFULL (EMBOSS version of NCBI NUC4.4) substitution matrix. The output of Needle labeled “longest identity” (obtained using the -nobrief option) is used as the percent identity and is calculated as follows:
(Identical Deoxyribonucleotides×100)/(Length of Alignment−Total Number of Gaps in Alignment)
Variant: The term “variant” means a polypeptide comprising an alteration, i.e., a substitution, insertion, and/or deletion, at one or more (e.g., several) positions compared to the corresponding parent polypeptide. A substitution means replacement of the amino acid occupying a position with a different amino acid; a deletion means removal of the amino acid occupying a position; and an insertion means adding one or more (e.g., several) amino acids, e.g., 1-5 amino acids, adjacent to the amino acid occupying a position.
Yield: The term “yield” means the expression yield or the activity yield of a heterologous polypeptide of interest upon co-expression of this polypeptide with a foldase that is cognate to the heterologous polypeptide of interest according to the methods of the present invention. Alpha-amylase activity yield of a polypeptide of interest may be determined according to Example 4 below. For other enzyme activities, activity assays are known in the art and readily available to the skilled person
The term “improved yield” means a relative improvement in expression yield or activity yield of a heterologous polypeptide of interest upon co-expression with foldase that is cognate to the heterologous polypeptide of interest in a Gram-positive host cell compared to the expression yield or activity yield of the same heterologous polypeptide of interest upon co-expression with a foldase that is non-cognate to the heterologous polypeptide of interest in a Gram-positive host cell of the same species. In one embodiment, the yield is on par or improved, e.g., at least 100%, at least 101%, at least 102%, at least 103%, at least 104%, at least 105%, at least 110%, at least 120%, at least 130%, at least 140%, at least 150%, at least 175%, at least 200%, at least 250%, at least 300%, at least 400%, at least 500%, or more.
SEQ ID NO:1: DNA sequence of B. amyloliquefaciens PrsA.
SEQ ID NO:2: B. amyloliquefaciens PrsA including signal peptide.
SEQ ID NO:3: B. amyloliquefaciens PrsA mature polypeptide.
SEQ ID NO:4: DNA sequence of B. amyloliquefaciens amylase (AmyQ).
SEQ ID NO:5: B. amyloliquefaciens amylase including signal peptide.
SEQ ID NO:6: B. amyloliquefaciens amylase mature polypeptide.
SEQ ID NO:7: DNA sequence of B. licheniformis PrsA.
SEQ ID NO:8: B. licheniformis PrsA including signal peptide.
SEQ ID NO:9: B. licheniformis PrsA mature polypeptide.
SEQ ID NO:10: DNA sequence of B. licheniformis amylase (AmyL).
SEQ ID NO:11: B. licheniformis amylase including signal peptide.
SEQ ID NO:12: B. licheniformis amylase mature polypeptide.
SEQ ID NO:13: DNA sequence of B. sp. NSP9.1 PrsA.
SEQ ID NO:14: B. sp. NSP9.1 PrsA including signal peptide.
SEQ ID NO:15: B. sp. NSP9.1 PrsA mature polypeptide.
SEQ ID NO:16: DNA sequence of B. sp. NSP9.1 amylase.
SEQ ID NO:17: B. sp. NSP9.1 amylase including signal peptide.
SEQ ID NO:18: B. sp. NSP9.1 amylase mature polypeptide.
SEQ ID NO:19: DNA sequence of B. sonorensis L12 PrsA.
SEQ ID NO:20: B. sonorensis L12 PrsA including signal peptide.
SEQ ID NO:21: B. sonorensis L12 PrsA mature polypeptide.
SEQ ID NO:22: DNA sequence of B. sonorensis L12 amylase.
SEQ ID NO:23: B. sonorensis L12 amylase including signal peptide.
SEQ ID NO:24: B. sonorensis L12 amylase mature polypeptide.
SEQ ID NO:25: DNA sequence of B. subtilis PrsA.
SEQ ID NO:26: B. subtilis PrsA including signal peptide.
SEQ ID NO:27: B. subtilis PrsA mature polypeptide.
SEQ ID NO:28: DNA sequence of B. subtilis amylase (AmyE).
SEQ ID NO:29: B. subtilis amylase including signal peptide.
SEQ ID NO:30: B. subtilis amylase mature polypeptide.
SEQ ID NO:31: DNA sequence of sigF gene.
SEQ ID NO:32: DNA sequence of sigF Δ297 bp.
SEQ ID NO:33: SOE PCR product for integration of a gene coding for PrsA from B. licheniformis in pel locus of AN2, AQG91.
SEQ ID NO:34: SOE PCR product for integration of a gene coding for AmyL of B. licheniformis in amyE locus of AN2, AQG91.
SEQ ID NO:35: SOE PCR product for integration of the the PhtrA-lacZ cassette in the xyl locus of B. subtilis.
The present invention relates to means and methods for optimizing expression of heterologous polypeptides in Gram-positive host cells.
The present invention is based on the surprising and inventive finding that cultivation of Gram-positive host cells co-expressing a heterologous polypeptide of interest with a foldase, e.g., PrsA, that is cognate to the heterologous polypeptide of interest provides on par or even improved expression of the heterologous polypeptide of interest. In addition, co-expression of a heterologous polypeptides of interest with a cognate foldase also provides on par or reduced secretion stress when compared to co-expression of the heterologous polypeptide of interest with a non-cognate foldase. Thus, co-expression of heterologous polypeptides of interest together with a cognate foldase provides a hitherto unknown option for optimizing polypeptide expression in Gram-positive host cells, which is highly desirable within industrial biotechnology.
In a first aspect, the present invention relates to a nucleic acid construct comprising:
a) a first heterologous promoter operably linked to at least one polynucleotide encoding a foldase; and
b) a second heterologous promotor operably linked to at least one polynucleotide encoding a polypeptide of interest;
wherein the foldase and the polypeptide of interest are from the same Gram-positive species.
The nucleic acid constructs of the invention comprise at least one (i.e., one or more, e.g., 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, or more) polynucleotide encoding a polypeptide of interest. In some embodiments, the nucleic acid constructs of the invention comprise two or more polynucleotides encoding two or more polypeptides of interest, wherein the two or more polypeptides of interest are the same or different polypeptide(s) of interest.
The polypeptide of interest may be any polypeptide. Preferably, the polypeptide of interest is secreted.
In a preferred embodiment, the polypeptide of interest comprises an enzyme; preferably the enzyme is selected from the group consisting of hydrolase, isomerase, ligase, lyase, oxidoreductase, or transferase; more preferably an aminopeptidase, amylase, carbohydrase, carboxypeptidase, catalase, cellobiohydrolase, cellulase, chitinase, cutinase, cyclodextrin glycosyltransferase, deoxyribonuclease, endoglucanase, esterase, alpha-galactosidase, beta-galactosidase, glucoamylase, alpha-glucosidase, beta-glucosidase, invertase, laccase, lipase, mannosidase, mutanase, nuclease, oxidase, pectinolytic enzyme, peroxidase, phosphodiesterase, phytase, polyphenoloxidase, proteolytic enzyme, ribonuclease, transglutaminase, xylanase, and beta-xylosidase; most preferably the polypeptide of interest is an amylase.
The nucleic acid constructs of the invention comprise polynucleotides that encode a foldase and a polypeptide of interest, wherein said foldase and said polypeptide of interest are selected from the same Gram-positive species. In a preferred embodiment, the foldase and the polypeptide of interest are selected from the same Bacillus species; preferably the Bacillus species is selected from the group consisting of Bacillus alkalophilus, Bacillus altitudinis, Bacillus amyloliquefaciens, B. amyloliquefaciens subsp. plantarum, Bacillus brevis, Bacillus circulans, Bacillus clausii, Bacillus coagulans, Bacillus firmus, Bacillus sp. NSP9.1, Bacillus lautus, Bacillus lentus, Bacillus licheniformis, Bacillus megaterium, Bacillus methylotrophicus, Bacillus pumilus, Bacillus safensis, Bacillus sonorensis L12, Bacillus stearothermophilus, Bacillus subtilis, and Bacillus thuringiensis cells; most preferably Bacillus species is selected from the group consisting of Bacillus amyloliquefaciens, Bacillus licheniformis, Bacillus sp. NSP9.1, Bacillus sonorensis L12, and Bacillus subtilis.
Although the foldase and polypeptide of interest are selected from the same species, the skilled person will acknowledge the naturally occurring sequence variance of polynucleotide and polypeptide sequences within the same species.
In a preferred embodiment, the foldase has a sequence identity of at least 80%, e.g., at least 85%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100%, to SED ID NO:3, and the polypeptide of interest is from B. amyloliquefaciens. Preferably, the polypeptide of interest is an amylase; more preferably the polypeptide of interest has a sequence identity of at least 80%, e.g., at least 85%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100%, to SEQ ID NO:6. Most preferably, the polypeptide of interest comprises or consists of SEQ ID NO:6.
In a preferred embodiment, the foldase has a sequence identity of at least 80%, e.g., at least 85%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100%, to SED ID NO:9, and the polypeptide of interest is from B. licheniformis. Preferably, the polypeptide of interest is an amylase; more preferably the polypeptide of interest has a sequence identity of at least 80%, e.g., at least 85%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100%, to SEQ ID NO:12. Most preferably, the polypeptide of interest comprises or consists of SEQ ID NO:12.
In a preferred embodiment, the foldase has a sequence identity of at least 80%, e.g., at least 85%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100%, to SED ID NO:15, and the polypeptide of interest is from B. sp. NSP9.1. Preferably, the polypeptide of interest is an amylase; more preferably the polypeptide of interest has a sequence identity of at least 80%, e.g., at least 85%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100%, to SEQ ID NO:18. Most preferably, the polypeptide of interest comprises or consists of SEQ ID NO:18.
In a preferred embodiment, the foldase has a sequence identity of at least 80%, e.g., at least 85%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100%, to SED ID NO:21, and the polypeptide of interest is from B. sonorensis L12. Preferably, the polypeptide of interest is an amylase; more preferably the polypeptide of interest has a sequence identity of at least 80%, e.g., at least 85%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100%, to SEQ ID NO:24. Most preferably, the polypeptide of interest comprises or consists of SEQ ID NO:24.
In a preferred embodiment, the foldase has a sequence identity of at least 80%, e.g., at least 85%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100%, to SED ID NO:27, and the polypeptide of interest is from B. subtilis. Preferably, the polypeptide of interest is an amylase; more preferably the polypeptide of interest has a sequence identity of at least 80%, e.g., at least 85%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100%, to SEQ ID NO:30. Most preferably, the polypeptide of interest comprises or consists of SEQ ID NO:30.
The nucleic acid constructs of the invention are operably linked to one or more control sequences that direct the expression of the polynucleotides in a suitable host cell under conditions compatible with the control sequences.
The polynucleotide may be manipulated in a variety of ways to provide for expression of the polypeptide. Manipulation of the polynucleotide prior to its insertion into a vector may be desirable or necessary depending on the expression vector. The techniques for modifying polynucleotides utilizing recombinant DNA methods are well known in the art.
The control sequence may be a promoter, a polynucleotide that is recognized by a host cell for expression of a polynucleotide encoding a polypeptide of the present invention. The promoter contains transcriptional control sequences that mediate the expression of the polypeptide. The promoter may be any polynucleotide that shows transcriptional activity in the host cell including variant, truncated, and hybrid promoters, and may be obtained from genes encoding extracellular or intracellular polypeptides either homologous or heterologous to the host cell.
Examples of suitable promoters for directing transcription of the nucleic acid constructs of the present invention in a bacterial host cell are the promoters obtained from the Bacillus amyloliquefaciens alpha-amylase gene (amyQ), Bacillus licheniformis alpha-amylase gene (amyL), Bacillus licheniformis penicillinase gene (penP), Bacillus stearothermophilus maltogenic amylase gene (amyM), Bacillus subtilis levansucrase gene (sacB), Bacillus subtilis xylA and xylB genes, Bacillus thuringiensis cryIIIA gene (Agaisse and Lereclus, 1994, Molecular Microbiology 13: 97-107), E. coli lac operon, E. coli trc promoter (Egon et al., 1988, Gene 69: 301-315), Streptomyces coelicolor agarase gene (dagA), and prokaryotic beta-lactamase gene (Villa-Kamaroff et al., 1978, Proc. Natl. Acad. Sci. USA 75: 3727-3731), as well as the tac promoter (DeBoer et al., 1983, Proc. Natl. Acad. Sci. USA 80: 21-25). Further promoters are described in “Useful proteins from recombinant bacteria” in Gilbert et al., 1980, Scientific American 242: 74-94; and in Sambrook et al., 1989, supra. Examples of tandem promoters are disclosed in WO 99/43835.
Preferably, the first heterologous promotor and the second heterologous promoter are identical copies of the same heterologous promoter.
The control sequence may also be a transcription terminator, which is recognized by a host cell to terminate transcription. The terminator is operably linked to the 3′-terminus of the polynucleotide encoding the polypeptide. Any terminator that is functional in the host cell may be used in the present invention.
Preferred terminators for bacterial host cells are obtained from the genes for Bacillus clausii alkaline protease (aprH), Bacillus licheniformis alpha-amylase (amyL), and Escherichia coli ribosomal RNA (rrnB).
The control sequence may also be an mRNA stabilizer region downstream of a promoter and upstream of the coding sequence of a gene which increases expression of the gene.
Examples of suitable mRNA stabilizer regions are obtained from a Bacillus thuringiensis cryIIIA gene (WO 94/25612) and a Bacillus subtilis SP82 gene (Hue et al., 1995, Journal of Bacteriology 177: 3465-3471).
The control sequence may also be a signal peptide coding region that encodes a signal peptide linked to the N-terminus of a polypeptide and directs the polypeptide into the cell's secretory pathway. The 5′-end of the coding sequence of the polynucleotide may inherently contain a signal peptide coding sequence naturally linked in translation reading frame with the segment of the coding sequence that encodes the polypeptide. Alternatively, the 5′-end of the coding sequence may contain a signal peptide coding sequence that is foreign to the coding sequence. A foreign signal peptide coding sequence may be required where the coding sequence does not naturally contain a signal peptide coding sequence. Alternatively, a foreign signal peptide coding sequence may simply replace the natural signal peptide coding sequence in order to enhance secretion of the polypeptide. However, any signal peptide coding sequence that directs the expressed polypeptide into the secretory pathway of a host cell may be used.
Effective signal peptide coding sequences for bacterial host cells are the signal peptide coding sequences obtained from the genes for Bacillus NCI B 11837 maltogenic amylase, Bacillus licheniformis subtilisin, Bacillus licheniformis beta-lactamase, Bacillus stearothermophilus alpha-amylase, Bacillus stearothermophilus neutral proteases (nprT, nprS, nprM), and Bacillus subtilis prsA. Further signal peptides are described by Simonen and Palva, 1993, Microbiological Reviews 57: 109-137.
The control sequence may also be a propeptide coding sequence that encodes a propeptide positioned at the N-terminus of a polypeptide. The resultant polypeptide is known as a proenzyme or propolypeptide (or a zymogen in some cases). A propolypeptide is generally inactive and can be converted to an active polypeptide by catalytic or autocatalytic cleavage of the propeptide from the propolypeptide. The propeptide coding sequence may be obtained from the genes for Bacillus subtilis alkaline protease (aprE) and Bacillus subtilis neutral protease (nprT).
Where both signal peptide and propeptide sequences are present, the propeptide sequence is positioned next to the N-terminus of a polypeptide and the signal peptide sequence is positioned next to the N-terminus of the propeptide sequence.
It may also be desirable to add regulatory sequences that regulate expression of the polypeptide relative to the growth of the host cell. Examples of regulatory sequences are those that cause expression of the gene to be turned on or off in response to a chemical or physical stimulus, including the presence of a regulatory compound. Regulatory sequences in prokaryotic systems include the lac, tac, and trp operator systems.
The present invention also relates to polynucleotides encoding a foldase and polynucleotides encoding a polypeptide of interest, as described herein. In an embodiment, the polynucleotides encoding foldases and polypeptides of interest have been isolated.
The techniques used to isolate or clone a polynucleotide are known in the art and include isolation from genomic DNA or cDNA, or a combination thereof. The cloning of the polynucleotides from genomic DNA can be effected, e.g., by using the well-known polymerase chain reaction (PCR) or antibody screening of expression libraries to detect cloned DNA fragments with shared structural features. See, e.g., Innis et al., 1990, PCR: A Guide to Methods and Application, Academic Press, New York. Other nucleic acid amplification procedures such as ligase chain reaction (LCR), ligation activated transcription (LAT) and polynucleotide-based amplification (NASBA) may be used. The polynucleotides may be cloned from a strain of Bacillus, or a related organism and thus, for example, may be an allelic or species variant of the polypeptide encoding region of the polynucleotide.
Modification of a polynucleotide encoding a foldase or a polypeptide of interest of the present invention may be necessary for synthesizing polypeptides substantially similar to said polypeptides. The term “substantially similar” to the polypeptides refers to non-naturally occurring forms of the polypeptides.
The present invention also relates to recombinant expression vectors comprising a polynucleotide of the present invention, a promoter, and transcriptional and translational stop signals. The various nucleotide and control sequences may be joined together to produce a recombinant expression vector that may include one or more convenient restriction sites to allow for insertion or substitution of the polynucleotide encoding the polypeptide at such sites. Alternatively, the polynucleotide may be expressed by inserting the polynucleotide or a nucleic acid construct comprising the polynucleotide into an appropriate vector for expression. In creating the expression vector, the coding sequence is located in the vector so that the coding sequence is operably linked with the appropriate control sequences for expression.
The recombinant expression vector may be any vector (e.g., a plasmid or virus) that can be conveniently subjected to recombinant DNA procedures and can bring about expression of the polynucleotide. The choice of the vector will typically depend on the compatibility of the vector with the host cell into which the vector is to be introduced. The vector may be a linear or closed circular plasmid.
The vector may be an autonomously replicating vector, i.e., a vector that exists as an extrachromosomal entity, the replication of which is independent of chromosomal replication, e.g., a plasmid, an extrachromosomal element, a minichromosome, or an artificial chromosome. The vector may contain any means for assuring self-replication. Alternatively, the vector may be one that, when introduced into the host cell, is integrated into the genome and replicated together with the chromosome(s) into which it has been integrated. Furthermore, a single vector or plasmid or two or more vectors or plasmids that together contain the total DNA to be introduced into the genome of the host cell, or a transposon, may be used.
The vector preferably contains one or more selectable markers that permit easy selection of transformed, transfected, transduced, or the like cells. A selectable marker is a gene the product of which provides for biocide or viral resistance, resistance to heavy metals, prototrophy to auxotrophs, and the like.
Examples of bacterial selectable markers are Bacillus licheniformis or Bacillus subtilis dal genes, or markers that confer antibiotic resistance such as ampicillin, chloramphenicol, kanamycin, neomycin, spectinomycin, or tetracycline resistance.
The vector preferably contains an element(s) that permits integration of the vector into the host cell's genome or autonomous replication of the vector in the cell independent of the genome.
For integration into the host cell genome, the vector may rely on the polynucleotide's sequence encoding the polypeptide or any other element of the vector for integration into the genome by homologous or non-homologous recombination. Alternatively, the vector may contain additional polynucleotides for directing integration by homologous recombination into the genome of the host cell at a precise location(s) in the chromosome(s). To increase the likelihood of integration at a precise location, the integrational elements should contain a sufficient number of nucleic acids, such as 100 to 10,000 base pairs, 400 to 10,000 base pairs, and 800 to 10,000 base pairs, which have a high degree of sequence identity to the corresponding target sequence to enhance the probability of homologous recombination. The integrational elements may be any sequence that is homologous with the target sequence in the genome of the host cell. Furthermore, the integrational elements may be non-encoding or encoding polynucleotides. On the other hand, the vector may be integrated into the genome of the host cell by non-homologous recombination.
For autonomous replication, the vector may further comprise an origin of replication enabling the vector to replicate autonomously in the host cell in question. The origin of replication may be any plasmid replicator mediating autonomous replication that functions in a cell. The term “origin of replication” or “plasmid replicator” means a polynucleotide that enables a plasmid or vector to replicate in vivo.
Examples of bacterial origins of replication are the origins of replication of plasmids pUB110, pE194, pTA1060, and pAMβ1 permitting replication in Bacillus.
More than one copy of a polynucleotide of the present invention may be inserted into a host cell to increase production of a polypeptide. An increase in the copy number of the polynucleotide can be obtained by integrating at least one additional copy of the sequence into the host cell genome or by including an amplifiable selectable marker gene with the polynucleotide where cells containing amplified copies of the selectable marker gene, and thereby additional copies of the polynucleotide, can be selected for by cultivating the cells in the presence of the appropriate selectable agent.
The procedures used to ligate the elements described above to construct the recombinant expression vectors of the present invention are well known to one skilled in the art (see, e.g., Sambrook et al., 1989, supra).
The present invention also relates to recombinant host cells, comprising polynucleotides of the present invention operably linked to one or more control sequences that direct their expression. A nucleic acid construct and/or expression vector comprising the polynucleotides is introduced into a host cell so that the construct or vector is maintained as a chromosomal integrant or as a self-replicating extra-chromosomal vector as described earlier. The term “host cell” encompasses any progeny of a parent cell that is not identical to the parent cell due to mutations that occur during replication. The choice of a host cell will to a large extent depend upon the gene encoding the polypeptide and its source.
The host cell may be any cell useful in the recombinant production of a polypeptide of interest of the present invention, e.g., a Gram-positive cell.
The Gram-positive host cell may be any Gram-positive cell. Gram-positive host cells include, but are not limited to, any Bacillus, Clostridium, Enterococcus, Lactobacillus, Lactococcus, Oceanobacillus, Staphylococcus, Streptococcus, and Streptomyces cell.
The Gram-positive host cell may be any Bacillus cell including, but not limited to, Bacillus alkalophilus, Bacillus altitudinis, Bacillus amyloliquefaciens, B. amyloliquefaciens subsp. plantarum, Bacillus brevis, Bacillus circulans, Bacillus clausii, Bacillus coagulans, Bacillus firmus, Bacillus sp. NSP9.1, Bacillus lautus, Bacillus lentus, Bacillus licheniformis, Bacillus megaterium, Bacillus methylotrophicus, Bacillus pumilus, Bacillus safensis, Bacillus sonorensis L12, Bacillus stearothermophilus, Bacillus subtilis, and Bacillus thuringiensis cells. Preferably, the Gram-positive host cell is a Bacillus cell selected from the group consisting of B. amyloliquefaciens, B. licheniformis, B. sp. NSP9.1, B. sonorensis L12, and B. subtilis.
The Gram-positive host cell may also be any Streptococcus cell including, but not limited to, Streptococcus equisimilis, Streptococcus pyogenes, Streptococcus uberis, and Streptococcus equi subsp. Zooepidemicus cells.
The Gram-positive host cell may also be any Streptomyces cell including, but not limited to, Streptomyces achromogenes, Streptomyces avermitilis, Streptomyces coelicolor, Streptomyces griseus, and Streptomyces lividans cells.
The introduction of DNA into a Bacillus cell may be effected by protoplast transformation (see, e.g., Chang and Cohen, 1979, Mol. Gen. Genet. 168: 111-115), competent cell transformation (see, e.g., Young and Spizizen, 1961, J. Bacteriol. 81: 823-829, or Dubnau and Davidoff-Abelson, 1971, J. Mol. Biol. 56: 209-221), electroporation (see, e.g., Shigekawa and Dower, 1988, Biotechniques 6: 742-751), or conjugation (see, e.g., Koehler and Thorne, 1987, J. Bacteriol. 169: 5271-5278).
The introduction of DNA into a Streptomyces cell may be effected by protoplast transformation, electroporation (see, e.g., Gong et al., 2004, Folia Microbiol. (Praha) 49: 399-405), conjugation (see, e.g., Mazodier et al., 1989, J. Bacteriol. 171: 3583-3585), or transduction (see, e.g., Burke et al., 2001, Proc. Natl. Acad. Sci. USA 98: 6289-6294).
The introduction of DNA into a Streptococcus cell may be effected by natural competence (see, e.g., Perry and Kuramitsu, 1981, Infect. Immun. 32: 1295-1297), protoplast transformation (see, e.g., Catt and Jollick, 1991, Microbios 68: 189-207), electroporation (see, e.g., Buckley et al., 1999, Appl. Environ. Microbiol. 65: 3800-3804), or conjugation (see, e.g., Clewell, 1981, Microbiol. Rev. 45: 409-436).
However, any method known in the art for introducing DNA into a host cell can be used.
In a preferred embodiment, the Gram-positive host cells of the invention comprise in their genome a nucleic acid construct comprising (a) a first heterologous promoter operably linked to at least one polynucleotide encoding a foldase and (b) a second heterologous promotor operably linked to at least one polynucleotide encoding a polypeptide of interest, wherein the foldase and the polypeptide of interest are from the same Gram-positive species.
In an alternative embodiment, the at least one polynucleotide encoding a foldase and the at least one polynucleotide encoding a polypeptide of interest are operably linked with the same heterologous promotor in an operon.
The present invention also relates to methods for producing a polypeptide of interest, the method comprising:
a) providing a Gram-positive host cell of the invention comprising a nucleic acid construct and/or expression vector of the invention;
b) cultivating said host cell under conditions conducive for expression of the foldase and the polypeptide of interest; and, optionally
c) recovering the polypeptide of interest.
In an aspect, the present invention relates to a method for producing a polypeptide of interest, the method comprising:
In an embodiment, the Gram-positive host cell is a Bacillus cell. In another aspect, the Gram-positive host cell is a Bacillus licheniformis cell.
The methods of the inventions provide on par or improved yield of the polypeptide of interest and/or on par or reduced secretion stress. Thus, the methods of the invention maintain or improve yield without simultaneously increasing the amount of secretion stress exerted on the host cell, which is very beneficial for large-scale polypeptide production.
In an embodiment, the yield of the polypeptide of interest is on par or improved, e.g., at least 100%, at least 101%, at least 102%, at least 103%, at least 104%, at least 105%, at least 110%, at least 120%, at least 130%, at least 140%, at least 150%, at least 175%, at least 200%, at least 250%, at least 300%, at least 400%, at least 500%, or more. In a preferred embodiment, the yield is improved, e.g., more than 100% such as at least 101%, at least 102%, at least 103%, at least 104%, at least 105%, at least 110%, at least 120%, at least 130%, at least 140%, at least 150%, at least 175%, at least 200%, at least 250%, at least 300%, at least 400%, at least 500%, or more.
In an embodiment, the secretion stress experienced by the Gram-positive host cell is on par or reduced. In a preferred embodiment, the secretion stress is reduced. Most preferably the secretion stress is reduced by at least 1%, e.g., at least 2%, at least 3%, at least 4%, at least 5%, at least 10%, at least 15%, at least 20%, at least 25%, at least 30%, at least 35%, at least 40%, at least 45%, at least 50%, at least 75%, or more.
In an embodiment, the yield of the polypeptide of interest is improved and the secretion stress experienced by the Gram-positive host cell is on par or reduced.
In an embodiment, the yield of the polypeptide of interest is on par and the secretion stress experienced by the Gram-positive host cell is reduced.
In an embodiment, the yield of the polypeptide of interest is improved and the secretion stress experienced by the Gram-positive host cell is reduced.
The Gram-positive host cells are cultivated in a nutrient medium suitable for production of the polypeptide of interest using methods known in the art. For example, the cells may be cultivated by shake flask cultivation, or small-scale or large-scale fermentation (including continuous, batch, fed-batch, or solid-state fermentations) in laboratory or industrial fermentors in a suitable medium and under conditions allowing the polypeptide to be expressed and/or isolated. The cultivation takes place in a suitable nutrient medium comprising carbon and nitrogen sources and inorganic salts, using procedures known in the art. Suitable media are available from commercial suppliers or may be prepared according to published compositions (e.g., in catalogues of the American Type Culture Collection). If the polypeptide of interest is secreted into the nutrient medium, the polypeptide of interest can be recovered directly from the medium. If the polypeptide of interest is not secreted, it can be recovered from cell lysates.
The polypeptide of interest may be detected using methods known in the art that are specific for the polypeptide of interest. These detection methods include, but are not limited to, use of specific antibodies, formation of an enzyme product, or disappearance of an enzyme substrate. For example, an enzyme assay may be used to determine the activity of the polypeptide of interest.
The polypeptide of interest may be recovered using methods known in the art. For example, the polypeptide may be recovered from the nutrient medium by conventional procedures including, but not limited to, collection, centrifugation, filtration, extraction, spray-drying, evaporation, or precipitation. In one aspect, a fermentation broth comprising the polypeptide of interest is recovered.
The polypeptide of interest may be purified by a variety of procedures known in the art including, but not limited to, chromatography (e.g., ion exchange, affinity, hydrophobic, chromatofocusing, and size exclusion), electrophoretic procedures (e.g., preparative isoelectric focusing), differential solubility (e.g., ammonium sulfate precipitation), SDS-PAGE, or extraction (see, e.g., Protein Purification, Janson and Ryden, editors, VCH Publishers, New York, 1989) to obtain substantially pure polypeptides.
In an alternative aspect, the polypeptide of interest is not recovered, but rather a host cell of the present invention expressing the polypeptide of interest is used as a source of the polypeptide of interest.
In further aspects, the present invention also relates to a fermentation broth formulation or a cell composition comprising a polypeptide of interest. The fermentation broth product further comprises additional ingredients used in the fermentation process, such as, for example, cells (including, the host cells containing the gene encoding the polynucletotide(s) which are used to produce the polypeptide of interest), cell debris, biomass, fermentation media and/or fermentation products. In some embodiments, the composition is a cell-killed whole broth containing organic acid(s), killed cells and/or cell debris, and culture medium.
The term “fermentation broth” as used herein refers to a preparation produced by cellular fermentation that undergoes no or minimal recovery and/or purification. For example, fermentation broths are produced when microbial cultures are grown to saturation, incubated under carbon-limiting conditions to allow protein synthesis (e.g., expression of enzymes by host cells) and secretion into cell culture medium. The fermentation broth can contain unfractionated or fractionated contents of the fermentation materials derived at the end of the fermentation. Typically, the fermentation broth is unfractionated and comprises the spent culture medium and cell debris present after the microbial cells are removed, e.g., by centrifugation. In some embodiments, the fermentation broth contains spent cell culture medium, extracellular enzymes, and viable and/or nonviable microbial cells.
In an embodiment, the fermentation broth formulation and cell compositions comprise a first organic acid component comprising at least one 1-5 carbon organic acid and/or a salt thereof and a second organic acid component comprising at least one 6 or more carbon organic acid and/or a salt thereof. In a specific embodiment, the first organic acid component is acetic acid, formic acid, propionic acid, a salt thereof, or a mixture of two or more of the foregoing and the second organic acid component is benzoic acid, cyclohexanecarboxylic acid, 4-methylvaleric acid, phenylacetic acid, a salt thereof, or a mixture of two or more of the foregoing.
In one aspect, the composition contains an organic acid(s), and optionally further contains killed cells and/or cell debris. In one embodiment, the killed cells and/or cell debris are removed from a cell-killed whole broth to provide a composition that is free of these components.
The fermentation broth formulations or cell compositions may further comprise a preservative and/or anti-microbial (e.g., bacteriostatic) agent, including, but not limited to, sorbitol, sodium chloride, potassium sorbate, and others known in the art.
The cell-killed whole broth or composition may contain the unfractionated contents of the fermentation materials derived at the end of the fermentation. Typically, the cell-killed whole broth or composition contains the spent culture medium and cell debris present after the microbial cells (e.g., filamentous fungal cells) are grown to saturation, incubated under carbon-limiting conditions to allow protein synthesis. In some embodiments, the cell-killed whole broth or composition contains the spent cell culture medium, extracellular enzymes, and killed filamentous fungal cells. In some embodiments, the microbial cells present in the cell-killed whole broth or composition can be permeabilized and/or lysed using methods known in the art.
A whole broth or cell composition as described herein is typically a liquid, but may contain insoluble components, such as killed cells, cell debris, culture media components, and/or insoluble enzyme(s). In some embodiments, insoluble components may be removed to provide a clarified liquid composition.
The whole broth formulations and cell compositions of the present invention may be produced by a method described in WO 1990/15861 or WO 2010/096673.
1) A nucleic acid construct comprising:
The present invention is further described by the following examples that should not be construed as limiting the scope of the invention.
Chemicals used as buffers and substrates were commercial products of at least reagent grade.
PCR amplifications were performed using standard textbook procedures, employing a commercial thermocycler and either Ready-To-Go PCR beads, Phusion polymerase, or RED-TAQ polymerase from commercial suppliers.
LB agar: See EP 0 506 780.
LBPSG agar plates contains LB agar supplemented with phosphate (0.01 M K3PO4), glucose (0.4%), and starch (0.5%); See EP 0 805 867 B1.
TY (liquid broth medium): See WO 94/14968, p. 16.
Oligonucleotide primers were obtained from Eurofins, Aarhus, Denmark. DNA manipulations (plasmid and genomic DNA preparation, restriction digestion, purification, ligation, DNA sequencing) was performed using standard textbook procedures with commercially available kits and reagents.
DNA was introduced into B. subtilis rendered naturally competent, either using a two-step procedure (Yasbin et al., 1975, J. Bacteriol. 121: 296-304), or a one-step procedure, in which cell material from an agar plate was resuspended in Spizisen 1 medium (WO 2014/052630), 12 ml shaken at 200 rpm for approx. 4 hours at 37° C., DNA added to 400 microliter aliquots, and these further shaken 150 rpm for 1 hour at the desired temperature before plating on selective agar plates.
All of the constructions described in the examples were assembled from synthetic DNA fragments ordered from GeneArt-ThermoFisher Scientific. The fragments were assembled by sequence overlap extension (SOE) as described in the Examples.
Genomic DNA was prepared from all relevant isolates by using the commercial available QIAamp DNA Blood Kit from Qiagen.
The BioLector® is a microfermentation system that monitors online common fermentation parameters such as biomass, pH, oxygen saturation and fluorescence. It contains a temperature and humidity controlled incubation chamber that carries a single microplate. The fermentation can be monitored continuously by an optical fiber that moves below the plate. In this work, a BioLector®(m2p-Labs, Baesweiler, Germany) was used for the measurement of scattered light and GFP fluorescence. Cultivations were performed in LB media, at a shaking frequency of 1000 rpm, 37° C. and 85% humidity in 48-well Flowerplates® (M2p-labs), covered with a Sealing Foil with Reduced Evaporation (M2p-Labs). Fermentations were carried out in biological triplicates for 24 hours, and the supernatants harvested for subsequent amylase activity measurements.
After 24 hours of fermentation, the Flowerplates® were centrifuged at 3500 rpm for 20 minutes at 4° C. 20 ul of the supernatant was transferred in technical duplicates to 96-well plates. A calibration curve with increasing concentrations of BAN amylase (0-500 UCF/ul, Novozymes in-house product) was added to each 96 well plate. AmyL (Roche/Hitachi) Reagent 1 (66 mL) and Reagent 2 (16 mL) were mixed and 180 ul of the mixture was added to the plate. The colorimetric reaction was measured in a Cytation5 plate reader at 405 nm, 23° C. for 6 minutes, measuring absorbance each minute.
B. subtilis AN2 was used as a host strain for expression of prsA and amylase genes as described in the following Examples. AN2 is a sporulation deficient derivative of B. subtilis 168 due to deletion of 297 bp in the sigF gene (the sigF sequence is provided as SEQ ID NO: 31 and the inactive version containing the deletion is provided as SEQ ID NO:32).
The B. subtilis strain AN2 was used as a host strain for insertion of expression cassettes for heterologous copies of the prsA gene. PrsA expression cassettes were integrated into the pel locus and consisted of the synthetic promoter PconSD followed by a prsA gene and the B. subtilis prsA native terminator. DNA for integrations can be assembled by PCR amplifications of synthetic DNA consisting of the following DNA components: pel 5′ region+ermC (conferring resistance to erythromycin)+synthetic consensus promoter with SD sequence (PconsSD)+prsA open reading frame with terminator+pel 3′ region. The purified PCR products were used in subsequent PCR reactions to create single linear DNA by the Gene Splicing by Overlapping Extension (SOE) method (Horton RM 1989) and the Phusion Hot Start DNA Polymerase system (Thermo Scientific) as follows. The PCR amplification reaction mixture contained 50 ng of each of the gel purified PCR products and a thermocycler was used to assemble and amplify the DNA. The resulting SOE product was used directly for transformation of the B. subtilis host AN2. Chromosomal integration was facilitated by homologous recombination and cells in where double cross over events occurred were selected for on LB agar plates containing 1 μg/ml erythromycin. A schematic view of a linear DNA product used for integration of a prsA gene in AN2 is shown in
Alpha-amylase expression cassettes were integrated into the amyE loci of B. subtilis AN2, AQG91, AQG34, AQG92, AQG159 and AQG162 and consisted of the synthetic promoter PconSD followed by an alpha-amylase gene and the B. amyloliquefaciens amyQ terminator. The amyE gene becomes inactivated in this process. DNA for integration can be assembled by PCR amplifications of synthetic DNA consisting of the following DNA components: amyE 5′ region+synthetic consensus promoter with SD sequence (PconsSD)+an alpha-amylase open reading frame+the B. amyloliquefaciens amyQ terminator+the cat gene (conferring resistance to chloramphenicol)+amyE 3′ region. The genes encoding alpha-amylases used in this example are SEQ ID NO:4 (encoding B. amyloliquefaciens AmyQ), SEQ ID NO:10 (encoding B. licheniformis AmyL, SEQ ID NO:16 (encoding B. sp. NSP9.1 Amy9.1), SEQ ID NO:22 (encoding B. sonorensis L12 AmyL12), and SEQ ID NO:28 (encoding B. subtilis AmyE). The purified PCR products were used in subsequent PCR reactions to create single linear DNA by the SOE method described in Example 2. The resulting SOE products were used directly for transformation of the B. subtilis strains described in Example 2 and a schematic view of such a DNA product (used for integration of the amyL gene in AQG91) is shown in
The B. subtilis strains constructed in Example 3 were tested with respect to alpha-amylase productivity in batch cultivations as described above. For batch cultivations we used the BioLector® microfermentation system that contains a temperature and humidity controlled incubation chamber and monitors common fermentation parameters online. Cultivations were carried out in biological triplicates for 24 hours, after which the supernatant was harvested for subsequent amylase activity measurements as described above. Table 2 shows amylase activities measured in supernatants from each series of strains co-expressing a specific amylase and the various heterologous prsA genes as described in Example 3. Values in each series are set relative to the strain which express the amylase from the amyE locus but which do not co-express any PrsA from the pel locus.
The table reveals that the highest amylase activities in the far majority of cases were obtained when the heterologous amylase was co-expressed with its cognate PrsA in B. subtilis. Other than cognate combinations of amylase and prsA genes that resulted in increased amylase activity were also observed, but none of these were superior to a cognate pair (Table 2).
B. sp.
B. subtilis
B. licheniformis
B. amyloliquefaciens
B. sonorensis
B. subtilis
B. licheniformis
B. amyloliquefaciens
B. sonorensis
B. sp.
As an indicator for secretion stress imposed by amylase production on the B. subtilis strains described in the previous Examples, we employed a promoter fusion between the secretion stress-inducible htrA promoter (PhtrA) and the lacZ gene. A LacZ expression cassette under the control of the htrA promoter and targeting the xyl locus was assembled by SOE PCR using the following synthetic DNA components: 5′ xyl region+a spc gene (conferring resistance to spectinomycin)+the native B. subtilis htrA promoter+the lacZ gene+3′ xyl region. The purified PCR products were used in a subsequent PCR reaction to create a single linear DNA by the SOE method described in Example 2. A schematic view of the linear DNA product used for integration of the PhtrA-lacZ cassette into the xyl locus of B. subtilis is shown in
The SOE product described in Example 5 was used directly for transformation of the B. subtilis strains AQG77, AQG97, AGQ98, AQG126, AQG174 and AQG657 resulting in strains AN2370, AN2372, AN2368, AN2376, AN2373, and AN2377. Chromosomal integration was facilitated by homologous recombination and cells wherein double cross-over events occurred were selected for on LB agar plates containing 120 μg/ml spectinomycin.
The B. subtilis strains constructed in Example 6 were tested with respect to beta-galactosidase productivity in batch cultivations. Cultivations were carried out in biological triplicates for 24 hours, after which the supernatant was harvested for subsequent beta-galactosidase activity measurements as described above. The table below lists the beta-galactosidase activities measured in 24 hours old cultures of B. subtilis AN2370, AN2372, AN2368, AN2376, AN2373, and AN2377. The table reveals that co-expression of a heterologous polypeptide of interest with a cognate foldase not only results in increased alpha-amylase activity but also leads to a significant decrease in activity of the htrA promoter. Thus, co-expression of B. licheniformis PrsA provides the highest degree of alleviation of secretion stress in the AmyL-producing AN2 derivative AN2372 described in Example 6.
In conclusion, co-expression of a heterologous polypeptide with a cognate PrsA reduces secretion stress compared to co-expression of same heterologous polypeptide with a non-cognate PrsA.
| Number | Date | Country | Kind |
|---|---|---|---|
| 19154510.2 | Jan 2019 | EP | regional |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2020/051505 | 1/22/2020 | WO | 00 |
