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Li C, Zhou J, Du G, Chen J, Takahashi S, Liu S. Developing Aspergillus niger as a cell factory for food enzyme production. Biotechnol Adv 2020; 44:107630. [PMID: 32919011 DOI: 10.1016/j.biotechadv.2020.107630] [Citation(s) in RCA: 28] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2020] [Revised: 09/05/2020] [Accepted: 09/05/2020] [Indexed: 02/06/2023]
Abstract
Aspergillus niger has become one of the most important hosts for food enzyme production due to its unique food safety characteristics and excellent protein secretion systems. A series of food enzymes such as glucoamylase have been commercially produced by A. niger strains, making this species a suitable platform for the engineered of strains with improved enzyme production. However, difficulties in genetic manipulations and shortage of expression strategies limit the progress in this regard. Moreover, several mycotoxins have recently been detected in some A. niger strains, which raises the necessity for a regulatory approval process for food enzyme production. With robust strains, processing engineering strategies are also needed for producing the enzymes on a large scale, which is also challenging for A. niger, since its culture is aerobic, and non-Newtonian fluid properties are developed during submerged culture, making mixing and aeration very energy-intensive. In this article, the progress and challenges of developing A. niger for the production of food enzymes are reviewed, including its genetic manipulations, strategies for more efficient production of food enzymes, and elimination of mycotoxins for product safety.
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Affiliation(s)
- Cen Li
- National Engineering Laboratory for Cereal Fermentation Technology, Jiangnan University, 1800 Lihu Road, Wuxi, Jiangsu 214122, China; School of Biotechnology and Key Laboratory of Industrial Biotechnology, Ministry of Education, Jiangnan University, 1800 Lihu Road, Wuxi, Jiangsu 214122, China.
| | - Jingwen Zhou
- National Engineering Laboratory for Cereal Fermentation Technology, Jiangnan University, 1800 Lihu Road, Wuxi, Jiangsu 214122, China; School of Biotechnology and Key Laboratory of Industrial Biotechnology, Ministry of Education, Jiangnan University, 1800 Lihu Road, Wuxi, Jiangsu 214122, China; Jiangsu Provisional Research Center for Bioactive Product Processing Technology, Jiangnan University, 1800 Lihu Road, Wuxi, Jiangsu 214122, China.
| | - Guocheng Du
- School of Biotechnology and Key Laboratory of Industrial Biotechnology, Ministry of Education, Jiangnan University, 1800 Lihu Road, Wuxi, Jiangsu 214122, China; The Key Laboratory of Carbohydrate Chemistry and Biotechnology, Ministry of Education, Jiangnan University, 1800 Lihu Road, Wuxi, Jiangsu 214122, China.
| | - Jian Chen
- National Engineering Laboratory for Cereal Fermentation Technology, Jiangnan University, 1800 Lihu Road, Wuxi, Jiangsu 214122, China; School of Biotechnology and Key Laboratory of Industrial Biotechnology, Ministry of Education, Jiangnan University, 1800 Lihu Road, Wuxi, Jiangsu 214122, China; Jiangsu Provisional Research Center for Bioactive Product Processing Technology, Jiangnan University, 1800 Lihu Road, Wuxi, Jiangsu 214122, China.
| | - Shunji Takahashi
- Natural Product Biosynthesis Research Unit, RIKEN Center for Sustainable Resource Science, 2-1 Hirosawa, Wako, Saitama, 351-0198, Japan.
| | - Song Liu
- National Engineering Laboratory for Cereal Fermentation Technology, Jiangnan University, 1800 Lihu Road, Wuxi, Jiangsu 214122, China; School of Biotechnology and Key Laboratory of Industrial Biotechnology, Ministry of Education, Jiangnan University, 1800 Lihu Road, Wuxi, Jiangsu 214122, China.
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The C-Type Lysozyme from the upper Gastrointestinal Tract of Opisthocomus hoatzin, the Stinkbird. Int J Mol Sci 2019; 20:ijms20225531. [PMID: 31698762 PMCID: PMC6887759 DOI: 10.3390/ijms20225531] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2019] [Revised: 10/31/2019] [Accepted: 11/01/2019] [Indexed: 01/07/2023] Open
Abstract
Muramidases/lysozymes are important bio-molecules, which cleave the glycan backbone in the peptidoglycan polymer found in bacterial cell walls. The glycoside hydrolase (GH) family 22 C-type lysozyme, from the folivorous bird Opisthocomus hoazin (stinkbird), was expressed in Aspergillus oryzae, and a set of variants was produced. All variants were enzymatically active, including those designed to probe key differences between the Hoatzin enzyme and Hen Egg White lysozyme. Four variants showed improved thermostability at pH 4.7, compared to the wild type. The X-ray structure of the enzyme was determined in the apo form and in complex with chitin oligomers. Bioinformatic analysis of avian GH22 amino acid sequences showed that they separate out into three distinct subgroups (chicken-like birds, sea birds and other birds). The Hoatzin is found in the "other birds" group and we propose that this represents a new cluster of avian upper-gut enzymes.
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Production of recombinant proteins by filamentous fungi. Biotechnol Adv 2012; 30:1119-39. [DOI: 10.1016/j.biotechadv.2011.09.012] [Citation(s) in RCA: 164] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2011] [Revised: 08/30/2011] [Accepted: 09/15/2011] [Indexed: 11/17/2022]
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5
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James ER, van Zyl WH, van Zyl PJ, Görgens JF. Recombinant hepatitis B surface antigen production in Aspergillus niger: evaluating the strategy of gene fusion to native glucoamylase. Appl Microbiol Biotechnol 2012; 96:385-94. [DOI: 10.1007/s00253-012-4191-0] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2012] [Revised: 05/15/2012] [Accepted: 05/16/2012] [Indexed: 10/28/2022]
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6
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Casaite V, Bruzyte S, Bukauskas V, Setkus A, Morozova-Roche LA, Meskys R. Expression and purification of active recombinant equine lysozyme in Escherichia coli. Protein Eng Des Sel 2009; 22:649-54. [PMID: 19651623 DOI: 10.1093/protein/gzp048] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Equine lysozyme (EL) is a calcium (Ca)-binding lysozyme and is an intermediary link between non-Ca-binding C-type lysozyme and alpha-lactalbumin. The feature of lysozymes to assemble into the fibrils has recently gained considerable attention for the investigation of the functional properties of these proteins. To study the structural and functional properties of EL, a synthetic gene was cloned and EL was overexpressed in Escherichia coli as a fused protein. The His-tagged recombinant EL was accumulated as inclusion bodies. Up to 50 mg/l of the recombinant EL could be achieved after purification by Ni(2+) affinity chromatography, refolding in the presence of arginine, CM-Sepharose column purification following TEV protease cleavage. The purified protein was functionally active, as determined by the lysozyme activity, proving the proper folding of protein. The purified lysozyme was used for the oligomerisation studies. The protein formed amyloid fibrils during incubation in acidic pH and elevated temperature. The recombinant EL forms two types of fibrils: ring shaped and linear, similar to the native EL.
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Affiliation(s)
- Vida Casaite
- Department of Molecular Microbiology and Biotechnology, Institute of Biochemistry, Mokslininku 12, Vilnius LT-08662, Lithuania.
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O'Toole N, Min XJ, Butler G, Storms R, Tsang A. Sequence-Based Analysis of Fungal Secretomes. ACTA ACUST UNITED AC 2006. [DOI: 10.1016/s1874-5334(06)80015-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/20/2023]
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Ward OP, Qin WM, Dhanjoon J, Ye J, Singh A. Physiology and Biotechnology of Aspergillus. ADVANCES IN APPLIED MICROBIOLOGY 2005; 58C:1-75. [PMID: 16543029 DOI: 10.1016/s0065-2164(05)58001-8] [Citation(s) in RCA: 73] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Affiliation(s)
- O P Ward
- Department of Biology, University of Waterloo Waterloo, Ontario, Canada N2L 3G1
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Storms R, Zheng Y, Li H, Sillaots S, Martinez-Perez A, Tsang A. Plasmid vectors for protein production, gene expression and molecular manipulations in Aspergillus niger. Plasmid 2004; 53:191-204. [PMID: 15848224 DOI: 10.1016/j.plasmid.2004.10.001] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2004] [Revised: 09/23/2004] [Accepted: 10/04/2004] [Indexed: 10/26/2022]
Abstract
We constructed three sets of plasmids for use in Aspergillus niger. These plasmids were assembled using various combinations of a series of modular DNA cassettes that included a selectable marker, pyrG, derived from Aspergillus nidulans; two promoter regions for directing protein expression; a cassette derived from the AMA1 replicator sequence to support autonomous replication; and a reporter gene based on the A. niger lacA gene. One set included integrating and autonomously replicating plasmids for the expression of homologous and heterologous proteins. The second was a set of autonomously replicating plasmids, with a secreted beta-galactosidase encoding reporter gene, for studying gene regulation events. The third set included pyrG-derived gene-blaster cassettes suitable for genome manipulation by targeted gene replacement.
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Affiliation(s)
- Reginald Storms
- Centre for Structural and Functional Genomics, Concordia University, 7141 Sherbrooke Street West, Montreal, Que., Canada H4B 1R6.
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Paloheimo M, Mäntylä A, Kallio J, Suominen P. High-yield production of a bacterial xylanase in the filamentous fungus Trichoderma reesei requires a carrier polypeptide with an intact domain structure. Appl Environ Microbiol 2004; 69:7073-82. [PMID: 14660351 PMCID: PMC309970 DOI: 10.1128/aem.69.12.7073-7082.2003] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
A bacterial xylanase gene, Nonomuraea flexuosa xyn11A, was expressed in the filamentous fungus Trichoderma reesei from the strong cellobiohydrolase 1 promoter as fusions to a variety of carrier polypeptides. By using single-copy isogenic transformants, it was shown that production of this xylanase was clearly increased (up to 820 mg/liter) when it was produced as a fusion protein with a carrier polypeptide having an intact domain structure compared to the production (150 to 300 mg/liter) of fusions to the signal sequence alone or to carriers having incomplete domain structures. The carriers tested were the T. reesei mannanase I (Man5A, or MANI) core-hinge and a fragment thereof and the cellulose binding domain of T. reesei cellobiohydrolase II (Cel6A, or CBHII) with and without the hinge region(s) and a fragment thereof. The flexible hinge region was shown to have a positive effect on both the production of Xyn11A and the efficiency of cleavage of the fusion polypeptide. The recombinant Xyn11A produced had properties similar to those of the native xylanase. It constituted 6 to 10% of the total proteins secreted by the transformants. About three times more of the Man5A core-hinge carrier polypeptide than of the recombinant Xyn11A was observed. Even in the best Xyn11A producers, the levels of the fusion mRNAs were only approximately 10% of the level of cel7A (cbh1) mRNA in the untransformed host strain.
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Cardoza RE, Gutiérrez S, Ortega N, Colina A, Casqueiro J, Martín JF. Expression of a synthetic copy of the bovine chymosin gene in Aspergillus awamori from constitutive and pH-regulated promoters and secretion using two different pre-pro sequences. Biotechnol Bioeng 2003; 83:249-59. [PMID: 12783481 DOI: 10.1002/bit.10666] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
A copy of the bovine chymosin gene (chy) with a codon usage optimized for its expression in Aspergillus awamori was constructed starting from synthetic oligonucleotides. To study the ability of this filamentous fungus to secrete bovine prochymosin, two plasmids were constructed in which the transcriptional, translational, and secretory control regions of the A. nidulans gpdA gene and pepB genes were coupled to either preprochymosin or prochymosin genes. Secretion of a protein enzymatically and immunologically indistinguishable from bovine chymosin was achieved in A. awamori transformants with each of these constructions. In all cases, the primary translation product (40.5 kDa) was self-processed to a mature chymosin polypeptide having a molecular weight of 35.6 kDa. Immunological assays indicated that most of the chymosin was secreted to the extracellular medium. Hybridization analysis of genomic DNA from chymosin transformants showed chromosomal integration of prochymosin sequences and, in some transformants, multiple copies of the expression cassettes were observed. Expression from the gpdA promoter was constitutive, whereas expression from the pepB promoter was strongly influenced by pH. A very high expression from the pepB promoter was observed during the growth phase. The A. awamori pepB gene terminator was more favorable for chymosin production than the S. cerevisiae CYC1 terminator.
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Affiliation(s)
- R E Cardoza
- Institute of Biotechnology of León (INBIOTEC), Science Park of León, León, Spain
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Gordon CL, Archer DB, Jeenes DJ, Doonan JH, Wells B, Trinci AP, Robson GD. A glucoamylase::GFP gene fusion to study protein secretion by individual hyphae of Aspergillus niger. J Microbiol Methods 2000; 42:39-48. [PMID: 11000429 DOI: 10.1016/s0167-7012(00)00170-6] [Citation(s) in RCA: 67] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Although Aspergillus niger is used as a host for heterologous protein production, yields are generally lower than those obtained for homologous proteins. Mechanisms of protein secretion and the secretory pathway in filamentous fungi are poorly characterised, although there is evidence to suggest that secretion occurs by a mechanism similar to that in other eukaryotes, but with proteins destined for secretion being directed to the hyphal tip. We report on a method using a glucoamylase: GFP gene fusion which allows us for the first time to monitor, in vivo, protein secretion in A. niger at the single hyphal level. A synthetic green fluorescent protein (sGFP(S65T)) was fused to truncated A. niger glucoamylase (GLA:499). Southern blot analysis of transformants confirmed that the gene fusion had successfully integrated into the A. niger genome. Confocal and fluorescence microscopy revealed that the GLA::GFP fusion protein is fluorescent in A. niger and appears to be directed to the hyphal tip. In young mycelia, hyphal cell wall fluorescence is apparent and immunogold labelling of GFP confirmed that GFP was partially localised within the hyphal cell wall. Using Western blotting, extracellular GLA::GFP was detected only in culture filtrates of young mycelia grown in a soya milk medium. The actin inhibitor latrunculin B was used to disrupt the secretion process, and its effects on the distribution of GLA::GFP were monitored.
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Affiliation(s)
- C L Gordon
- 1.800 Stopford Building, School of Biological Sciences, University of Manchester, M13 9PT, Manchester, UK
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MacKenzie DA, Jeenes DJ, Gou X, Archer DB. Molecular basis of glucoamylase overproduction by a mutagenised industrial strain of Aspergillus niger. Enzyme Microb Technol 2000; 26:193-200. [PMID: 10689077 DOI: 10.1016/s0141-0229(99)00145-3] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
We have compared a mutagenized strain of Aspergillus niger (S1), used industrially for glucoamylase production, and a related low glucoamylase-producing strain (S2) with a laboratory strain of A. niger (AB4.1). Our aim was to assess the properties of S1 in relation to the laboratory strain and to account at the molecular level for the basis of its glucoamylase overproduction. Both S1 and S2 have similar multiple copies of the glucoamylase-encoding gene (glaA) but only S1 has enhanced glaA transcript and glucoamylase levels compared to AB4.1 that has a single copy of the glaA gene. Glucoamylase production by S1 and AB4.1 was repressed by xylose and induced by starch but, in S2, remained unaffected by carbon source. S1 also secreted elevated levels of alpha-amylase relative to both S2 and AB4.1 but the production of alpha-glucosidase was low in all three strains. The gene encoding aspergillopepsin (pepA), an abundant secreted aspartyl protease, was present as a single copy in all strains but no aspergillopepsin could be detected by Western blotting in either S1 or S2 culture supernatants. We conclude that A. niger strain improvement by mutagenesis and screening for glucoamylase overproduction has led to glaA gene multiplication and an expression defect in the pepA gene.
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Affiliation(s)
- DA MacKenzie
- Division of Food Safety Science, Institute of Food Research, Norwich Research Park, Colney, Norwich, UK
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Gordon CL, Khalaj V, Ram AFJ, Archer DB, Brookman JL, Trinci APJ, Jeenes DJ, Doonan JH, Wells B, Punt PJ, van den Hondel CAMJJ, Robson GD. Glucoamylase::green fluorescent protein fusions to monitor protein secretion in Aspergillus niger. MICROBIOLOGY (READING, ENGLAND) 2000; 146 ( Pt 2):415-426. [PMID: 10708380 DOI: 10.1099/00221287-146-2-415] [Citation(s) in RCA: 94] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
A glucoamylase::green fluorescent protein fusion (GLA::sGFP) was constructed which allows the green fluorescent protein to be used as an in vivo reporter of protein secretion in Aspergillus niger. Two secretory fusions were designed for secretion of GLA::sGFP which employed slightly different lengths of the glucoamylase protein (GLA499 and GLA514). Expression of GLA::sGFP revealed that fluorescence was localized in the hyphal cell walls and septa, and that fluorescence was most intense at hyphal apices. Extracellular GLA::sGFP was detectable by Western blotting only in the supernatant of young cultures grown in soya milk medium. In older cultures, acidification of the medium and induction of proteases were probably responsible for the loss of extracellular and cell wall fluorescence and the inability to detect GLA::sGFP by Western analysis. A strain containing the GLA::sGFP construct was subjected to UV mutagenesis and survivors screened for mutations in the general secretory pathway. Three mutants were isolated that were unable to form a halo on either starch or gelatin medium. All three mutants grew poorly compared to the parental strain. Fluorescence microscopy revealed that for two of the mutants, GLA::sGFP accumulated intracellularly with no evidence of wall fluorescence, whereas for the third mutant, wall fluorescence was observed with no evidence of intracellular accumulation. These results indicate that the GLA::sGFP fusion constructs can be used as convenient fluorescent markers to study the dynamics of protein secretion in vivo and as a tool in the isolation of mutants in the general secretory pathway.
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Affiliation(s)
- Caroline L Gordon
- School of Biological Sciences, Stopford Building, University of Manchester, Manchester M13 9PT, UK1
| | - Vahid Khalaj
- School of Biological Sciences, Stopford Building, University of Manchester, Manchester M13 9PT, UK1
| | - Arthur F J Ram
- Centre for Phytotechnology, Institute for Molecular Plant Sciences, Clusius Laboratory, Wassenaarseweg 64, 2333 Al Leiden, The Netherlands2
| | - David B Archer
- Department of Genetics and Microbiology, Institute of Food Research, Norwich Laboratory, Norwich Research Park, Colney, Norwich NR4 7UA, UK3
| | - Jayne L Brookman
- School of Biological Sciences, Stopford Building, University of Manchester, Manchester M13 9PT, UK1
| | - Anthony P J Trinci
- School of Biological Sciences, Stopford Building, University of Manchester, Manchester M13 9PT, UK1
| | - David J Jeenes
- Department of Genetics and Microbiology, Institute of Food Research, Norwich Laboratory, Norwich Research Park, Colney, Norwich NR4 7UA, UK3
| | - John H Doonan
- Department of Cell Biology, John Innes Centre, Colney Lane, Norwich NR4 7UH, UK5
| | - Brian Wells
- Department of Cell Biology, John Innes Centre, Colney Lane, Norwich NR4 7UH, UK5
| | - Peter J Punt
- TNO Nutrition and Food Research Institute, Department of Molecular Genetics and Gene Technology, Utrechtseweg 48, PO Box 360, 3700 AJ Zeist, The Netherlands4
| | - Cees A M J J van den Hondel
- TNO Nutrition and Food Research Institute, Department of Molecular Genetics and Gene Technology, Utrechtseweg 48, PO Box 360, 3700 AJ Zeist, The Netherlands4
| | - Geoffrey D Robson
- School of Biological Sciences, Stopford Building, University of Manchester, Manchester M13 9PT, UK1
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Ngiam C, Jeenes DJ, Punt PJ, Van Den Hondel CA, Archer DB. Characterization of a foldase, protein disulfide isomerase A, in the protein secretory pathway of Aspergillus niger. Appl Environ Microbiol 2000; 66:775-82. [PMID: 10653750 PMCID: PMC91895 DOI: 10.1128/aem.66.2.775-782.2000] [Citation(s) in RCA: 76] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Protein disulfide isomerase (PDI) is important in assisting the folding and maturation of secretory proteins in eukaryotes. A gene, pdiA, encoding PDIA was previously isolated from Aspergillus niger, and we report its functional characterization here. Functional analysis of PDIA showed that it catalyzes the refolding of denatured and reduced RNase A. pdiA also complemented PDI function in a Saccharomyces cerevisiae Deltapdi1 mutant in a yeast-based killer toxin assay. Levels of pdiA mRNA and PDIA protein were raised by the accumulation of unfolded proteins in the endoplasmic reticulum. This response of pdiA mRNA levels was slower and lower in magnitude than that of A. niger bipA, suggesting that the induction of pdiA is not part of the primary stress response. An increased level of pdiA transcripts was also observed in two A. niger strains overproducing a heterologous protein, hen egg white lysozyme (HEWL). Although overexpression of PDI has been successful in increasing yields of some heterologous proteins in S. cerevisiae, overexpression of PDIA did not increase secreted yields of HEWL in A. niger, suggesting that PDIA itself is not limiting for secretion of this protein. Downregulation of pdiA by antisense mRNA reduced the levels of microsomal PDIA activity by up to 50%, lowered the level of PDIA as judged by Western blots, and lowered the secreted levels of glucoamylase by 60 to 70%.
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Affiliation(s)
- C Ngiam
- Division of Food Safety Sciences, Institute of Food Research, Norwich Research Park, Colney, Norwich NR4 7UA, United Kingdom
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Mainwaring DO, Wiebe MG, Robson GD, Goldrick M, Jeenes DJ, Archer DB, Trinci AP. Effect of pH on hen egg white lysozyme production and evolution of a recombinant strain of Aspergillus niger. J Biotechnol 1999; 75:1-10. [PMID: 10510855 DOI: 10.1016/s0168-1656(99)00123-6] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
An Aspergillus niger strain (B1) transformed to produce mature hen egg white lysozyme (HEWL) from a glucoamylase fusion protein under control of the A. niger glucoamylase promoter was grown in glucose-limited chemostat culture at a dilution rate of 0.07 h-1 at various pH values. Maximum HEWL production (9.3 mg g-1; specific production rate = 0.65 mg g-1 per h) was obtained at pH 4.5. However, in chemostat culture, HEWL production was not stable at any pH tested. After 240 h in steady state, specific production decreased to only 0.03 +/- 0.01 and 0.24 +/- 0.02 mg g-1 per h at pH 6.5 and 4.5, respectively. Some isolates removed from the chemostat cultures had lost copies of the HEWL gene and when grown in shake flask cultures all of the isolates produced less HEWL than the parental strain. Morphological mutants with similar phenotypes were isolated at all pHs, but their rate of increase in the population was pH dependent, with cultures at low pH (< 4.5) being more morphologically stable than cultures at high (> 4.5) pH. The selective advantage of these mutants was also generally dependent on pH. Both yellow pigment producing mutants and brown sporulation mutants had higher selective advantages over the parental strain at high than at low pH, regardless of the pH at which they were isolated. However, the selective advantage of densely sporulating mutants was independent of pH.
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Affiliation(s)
- D O Mainwaring
- University of Manchester, School of Biological Sciences, UK
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Abstract
Enzymes from filamentous fungi are already widely exploited, but new applications for known enzymes and new enzymic activities continue to be found. In addition, enzymes from less amenable non-fungal sources require heterologous production and fungi are being used as the production hosts. In each case there is a need to improve production and to ensure quality of product. While conventional, mutagenesis-based, strain improvement methods will continue to be applied to enzyme production from filamentous fungi the application of recombinant DNA techniques is beginning to reveal important information on the molecular basis of fungal enzyme production and this knowledge is now being applied both in the laboratory and commercially. We review the current state of knowledge on the molecular basis of enzyme production by filamentous fungi. We focus on transcriptional and post-transcriptional regulation of protein production, the transit of proteins through the secretory pathway and the structure of the proteins produced including glycosylation.
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Affiliation(s)
- D B Archer
- Genetics and Microbiology Department, Institute of Food Research, Norwich, UK
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Jeenes DJ, Pfaller R, Archer DB. Isolation and characterisation of a novel stress-inducible PDI-family gene from Aspergillus niger. Gene 1997; 193:151-6. [PMID: 9256071 DOI: 10.1016/s0378-1119(97)00098-x] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Current strategies to improve the secretion of heterologous proteins in Aspergillus niger include the manipulation of chaperones and foldases specific to the endoplasmic reticulum (ER). A family of ER-specific proteins which share active-site homology wit protein disulfide isomerase (PDI) has been identified from other systems, many of which are inducible by agents which cause malfolding of proteins in the ER. Here we report identification of tigA from Aspergillus niger and erp38 from Neurospora crassa, two novel members of the PDI superfamily of proteins. TIGA and ERp38 show 66% identity at the amino acid level and are putative ER proteins. Both proteins show tandemly linked thiol-oxidoreductase domains followed by a functionally uncharacterised C-terminal domain. The most distal active site in TIGA is created by excision of a 66-bp intron. Although no Unfolded Protein Response elements can be seen in the tigA promoter, sequence homology has identified associated with protein trafficking (ERPTRE) in a gene encoding the related mammalian protein, ERp72, as well as a second motif conserved amongst the glucose-related protein family. Southern and dot blot analysis indicate that the tigA gene is present in single copy. Both the A. niger and N. crassa proteins show homology with a stress-inducible alfalfa, G1. Transcription of tigA is induced 2-3-fold after treatment with tunicamycin, an inhibitor of N-linked glycosylation. Strains overexpressing a heterologous protein show no increased tigA mRNA levels.
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Affiliation(s)
- D J Jeenes
- Department of Genetics and Microbiology, Institute of Food Research, Colney, Norwich, UK.
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Gouka RJ, Punt PJ, van den Hondel CA. Glucoamylase gene fusions alleviate limitations for protein production in Aspergillus awamori at the transcriptional and (post) translational levels. Appl Environ Microbiol 1997; 63:488-97. [PMID: 9023927 PMCID: PMC168339 DOI: 10.1128/aem.63.2.488-497.1997] [Citation(s) in RCA: 45] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
In this study we have analyzed the effects of a glucoamylase gene fusion on the mRNA levels and protein levels for the human interleukin-6 gene (hil6) and the guar alpha-galactosidase gene (aglA). Previously it was shown that production of nonfused alpha-galactosidase and hIL-6 in Aspergillus awamori was limited at transcriptional and (post)translational levels, respectively (R. J. Gouka, P. J. Punt, J. G. M. Hessing, and C. A. M. J. J. van den Hondel, Appl. Environ. Microbiol. 62:1951-1957, 1996). Vectors were constructed which contained either the hil6 or aglA gene fused to the Aspergillus niger glucoamylase gene (glaA) under control of the efficient 1,4-beta-endoxylanase A promoter and transcription terminator. For comparison, the vectors were integrated in a single copy at the pyrG locus of A. awamori. A glaA fusion to the 5' end of the hil6 gene resulted in a large increase in hIL-6 yield, whereas with a glaA fusion to the 3' end of the hil6 gene, almost no protein was produced. Nevertheless, the steady-state mRNA levels of both fusions were very similar and not clearly increased compared to those of a strain expressing nonfused hIL-6. Fusions of glaA to the 5' end of the wild-type guar aglA gene resulted in truncated mRNA lacking almost 900 bases (> 80%) of the aglA sequence. When the coding sequence of the wild-type aglA gene was replaced by a synthetic aglA gene with optimized Saccharomyces cerevisiae codon usage, full-length mRNA was obtained. Compared to a nonfused synthetic aglA gene, a glaA fusion with the synthetic aglA gene resulted in a 25-fold increase in the mRNA level and, as a consequence, a similar increase in the alpha-galactosidase protein level. The truncated transcripts derived from the wild-type aglA gene were further analyzed by nuclear run-on transcription assays. These experiments indicated that transcription elongation in the nucleus proceeded at least 400 bases downstream of the site where the truncation was determined, indicating that transcription elongation or premature termination was not the reason for the generation of truncated mRNAs. As the truncated mRNA also contained a poly(A) tail, truncation most likely occurs by incorrect processing of the aglA mRNA in the nucleus.
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Affiliation(s)
- R J Gouka
- Department of Molecular Genetics and Gene Technology, TNO Nutrition and Food Research Institute, Rijswijk, The Netherlands
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Kurzatkowski W, Törrönen A, Filipek J, Mach RL, Herzog P, Sowka S, Kubicek CP. Glucose-induced secretion of Trichoderma reesei xylanases. Appl Environ Microbiol 1996; 62:2859-65. [PMID: 8702278 PMCID: PMC168071 DOI: 10.1128/aem.62.8.2859-2865.1996] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
To produce two xylanases with Trichoderma reesei grown on glucose, recombinant strains which carry either the xyn1 or the xyn2 (xylanase I and II [XYN I and XYN II]-encoding) structural genes under the expression signals of the homologous pki1 (pyruvate kinase-encoding) gene were constructed. The two types of transformants secreted XYN I or II, respectively, during growth on glucose, as demonstrated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and immunostaining. The corresponding specific xylanase activities of the best transformants on glucose were 76 and 145 U/mg of protein for XYN I and XYN II, respectively, as opposed to that obtained by the parent strain (26 U/mg of protein). When related to the amount of biomass formed, however, they produced only about 4 to 5 U/g, in contrast to much higher activities (10 to 12 U/g) during growth on xylan. The ultrastructural location of XYN II in the transformant strain producing the highest constitutive XYN II formation (ATX2-12) was investigated by immunoelectron microscopy and compared with that in the wild-type strain growing on xylan. Cell extracts from both types of transformants grown on glucose exhibited a higher intracellular xylanase activity than did the parent strain grown on xylan. By using electron microscopy and immunogold labelling, XYN II was detected in the endoplasmic reticulum, Golgi-like vesicles, secretory vesicles, vacuoles, and cell walls. The immunolabel in the vacuoles was detected preferentially in subapical cells. When a recombinant strain which expressed xyn2 from the pki1 promoter was compared with the parent strain during growth on xylan, the former exhibited a less proliferated endoplasmic reticulum and a smaller number of secretory vesicles; however, a higher density of labelling was observed. The relationship of these findings to the efficacy of protein secretion during growth on glucose is discussed.
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Gouka RJ, Punt PJ, Hessing JG, van den Hondel CA. Analysis of heterologous protein production in defined recombinant Aspergillus awamori strains. Appl Environ Microbiol 1996; 62:1951-7. [PMID: 8787393 PMCID: PMC167973 DOI: 10.1128/aem.62.6.1951-1957.1996] [Citation(s) in RCA: 58] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
A study was carried out to obtain more insight into the parameters that determine the secretion of heterologous proteins from filamentous fungi. A strategy was chosen in which the mRNA levels and protein levels of a number of heterologous genes of different origins were compared. All genes were under control of the Aspergillus awamori 1,4-beta-endoxylanase A (exlA) expression signals and were integrated in a single copy at the A. awamori pyrG locus. A Northern (RNA) analysis showed that large differences occurred in the steady-state mRNA levels obtained with the various genes; those levels varied from high values for genes of fungal origin (A. awamori 1,4-beta-endoxylanase A, Aspergillus niger glucoamylase, and Thermomyces lanuginosa lipase) to low values for genes of nonfungal origin (human interleukin 6 and Cyamopsis tetragonoloba [guar] alpha-galactosidase). With the C. tetragonoloba alpha-galactosidase wild-type gene full-length mRNA was even undetectable. Surprisingly, small amounts of full-length mRNA could be detected when a C. tetragonoloba alpha-galactosidase gene with an optimized Saccharomyces cerevisiae codon preference was expressed. In all cases except human interleukin 6, the protein levels corresponded to the amounts expected on basis of the mRNA levels. For human interleukin 6, very low protein levels were observed, whereas relatively high steady-state mRNA levels were obtained. Our data suggest that intracellular protein degradation is the most likely explanation for the low levels of secreted human interleukin 6.
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Affiliation(s)
- R J Gouka
- TNO Nutrition and Food Research Institute, Department of Molecular Genetics and Gene Technology, Rijswijk, The Netherlands
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MacKenzie DA, Spencer JA, Le Gal-Coëffet MF, Archer DB. Efficient production from Aspergillus niger of a heterologous protein and an individual protein domain, heavy isotope-labelled, for structure-function analysis. J Biotechnol 1996; 46:85-93. [PMID: 8672288 DOI: 10.1016/0168-1656(95)00179-4] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Aspergillus niger has been used successfully to secrete proteins labelled with 13C and/or 15N to a specific activity of > 99% for high resolution NMR analysis. In the case of a heterologous protein, hen egg-white lysozyme, 15N single-labelled and 13C, 15N double-labelled forms were secreted at yields of 100-200 mg l-1 by optimising the type of carbon source used and the ratio of carbon to nitrogen. Another protein, the glucoamylase starch-binding domain from A. niger, was also produced as the 15N single-labelled form at 20-40 mg l-1.
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Affiliation(s)
- D A MacKenzie
- Institute of Food Research, Norwich Research Park, Colney, UK
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Archer DB, MacKenzie DA, Ridout MJ. Heterologous protein secretion by Aspergillus niger growing in submerged culture as dispersed or aggregated mycelia. Appl Microbiol Biotechnol 1995; 44:157-60. [PMID: 8579829 DOI: 10.1007/bf00164495] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
The secreted production of a heterologous enzyme, hen egg-white lysozyme, by Aspergillus niger was studied in shake flasks containing media of different initial viscosities. Raising the viscosity of the medium by addition of polyvinylpyrrolidone (PVP) brought about a transition in the form of growth from aggregated mycelia (pellets) to dispersed mycelia. The specific yield of lysozyme in cultures containing an initial concentration of 5% (w/v) starch was 8 mg lysozyme/g dry weight. Addition of 2% (w/v) PVP to the medium resulted in a specific yield of 14 mg lysozyme/g dry weight.
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Affiliation(s)
- D B Archer
- Institute of Food Research, Colney, Norwich, UK
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Le Gal-Coëffet MF, Jacks AJ, Sorimachi K, Williamson MP, Williamson G, Archer DB. Expression in Aspergillus niger of the starch-binding domain of glucoamylase. Comparison with the proteolytically produced starch-binding domain. EUROPEAN JOURNAL OF BIOCHEMISTRY 1995; 233:561-7. [PMID: 7588802 DOI: 10.1111/j.1432-1033.1995.561_2.x] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Glucoamylase 1 from Aspergillus niger is an economically important enzyme in many industrial processes. It hydrolyses granular starch and comprises two distinct domains, a catalytic and a starch-binding domain (SBD). We have transformed A. niger with an expression vector for the secretion of SBD for physico-chemical studies. This was achieved by introducing into the glucoamylase gene a short sequence encoding an endoproteolytic cleavage recognition site such that free SBD was secreted at yields up to 200 mg/l. Free SBD was also obtained by proteolytic digestion of full-length glucoamylase 1. Electrospray mass spectroscopy was used to determine the carbohydrate content of both SBDs. It revealed that the engineered one is more glycosylated: an average of three mannose residues compared to one for the proteolytically derived SBD. Sequencing results also suggest partial glycosylation for the three Thr residues involved (510, 511, 513). It is probable that the engineered SBD represents the true glycosylation level of the SBD in native glucoamylase. Binding of beta-cyclodextrin to the SBD was investigated. It was found that the stoichiometry and the spectral perturbation of Trp residues were identical for both SBDs, but the engineered SBD bound less strongly to the ligand. At high concentrations of beta-cyclodextrin relative to the estimated Kd values, the maximum absorbance changes were identical. The observed difference at low beta-cyclodextrin levels was probably due to the higher level of glycosylation of the expressed SBD. We conclude that the proteolytically derived and expressed starch binding domains both bind 2 mol beta-cyclodextrin/mol protein, but that the pattern of glycosylation and strength of binding are different.
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Affiliation(s)
- M F Le Gal-Coëffet
- Krebs Institute for Biomolecular Research, Department of Molecular Biology and Biotechnology, University of Sheffield, UK
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