1
|
Hess M, Paul SS, Puniya AK, van der Giezen M, Shaw C, Edwards JE, Fliegerová K. Anaerobic Fungi: Past, Present, and Future. Front Microbiol 2020; 11:584893. [PMID: 33193229 PMCID: PMC7609409 DOI: 10.3389/fmicb.2020.584893] [Citation(s) in RCA: 44] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2020] [Accepted: 09/29/2020] [Indexed: 11/13/2022] Open
Abstract
Anaerobic fungi (AF) play an essential role in feed conversion due to their potent fiber degrading enzymes and invasive growth. Much has been learned about this unusual fungal phylum since the paradigm shifting work of Colin Orpin in the 1970s, when he characterized the first AF. Molecular approaches targeting specific phylogenetic marker genes have facilitated taxonomic classification of AF, which had been previously been complicated by the complex life cycles and associated morphologies. Although we now have a much better understanding of their diversity, it is believed that there are still numerous genera of AF that remain to be described in gut ecosystems. Recent marker-gene based studies have shown that fungal diversity in the herbivore gut is much like the bacterial population, driven by host phylogeny, host genetics and diet. Since AF are major contributors to the degradation of plant material ingested by the host animal, it is understandable that there has been great interest in exploring the enzymatic repertoire of these microorganisms in order to establish a better understanding of how AF, and their enzymes, can be used to improve host health and performance, while simultaneously reducing the ecological footprint of the livestock industry. A detailed understanding of AF and their interaction with other gut microbes as well as the host animal is essential, especially when production of affordable high-quality protein and other animal-based products needs to meet the demands of an increasing human population. Such a mechanistic understanding, leading to more sustainable livestock practices, will be possible with recently developed -omics technologies that have already provided first insights into the different contributions of the fungal and bacterial population in the rumen during plant cell wall hydrolysis.
Collapse
Affiliation(s)
- Matthias Hess
- Systems Microbiology & Natural Product Discovery Laboratory, Department of Animal Science, University of California, Davis, Davis, CA, United States
| | - Shyam S. Paul
- Gut Microbiome Lab, ICAR-Directorate of Poultry Research, Indian Council of Agricultural Research, Hyderabad, India
| | - Anil K. Puniya
- Anaerobic Microbiology Lab, ICAR-National Dairy Research Institute, Dairy Microbiology Division, ICAR-National Dairy Research Institute, Karnal, India
| | - Mark van der Giezen
- Department of Chemistry, Bioscience and Environmental Engineering, University of Stavanger, Stavanger, Norway
| | - Claire Shaw
- Systems Microbiology & Natural Product Discovery Laboratory, Department of Animal Science, University of California, Davis, Davis, CA, United States
| | - Joan E. Edwards
- Laboratory of Microbiology, Wageningen University & Research, Wageningen, Netherlands
| | - Kateřina Fliegerová
- Laboratory of Anaerobic Microbiology, Institute of Animal Physiology and Genetics, Czech Academy of Sciences, Prague, Czechia
| |
Collapse
|
2
|
Guo J, Xie Y, Yu Z, Meng G, Wu Z. Effect of Lactobacillus plantarum expressing multifunctional glycoside hydrolases on the characteristics of alfalfa silage. Appl Microbiol Biotechnol 2019; 103:7983-7995. [PMID: 31468090 DOI: 10.1007/s00253-019-10097-6] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2019] [Revised: 07/31/2019] [Accepted: 08/21/2019] [Indexed: 12/31/2022]
Abstract
For the first time, Lactobacillus plantarum strains carrying heterologous genes encoding multifunctional glycoside hydrolases were constructed and used as additives for alfalfa silage. The chemical characteristics, nonstructural carbohydrate composition, and fermentation quality of alfalfa silage were examined. The supernatant of L. plantarum expressing CbXyn10C and Bgxg1 (LP11AG) showed activities on xylan, Avicel, and carboxymethylcellulose (CMC), while the supernatant of the wild-type L. plantarum showed no activity. When LP11AG was used as silage additive, the water-soluble carbohydrate content of alfalfa silage increased by 72%, 55%, and 155% compared with control when the silage was stored at 20 °C, 30 °C, and 40 °C, respectively. With LP11AG being used as an additive for the alfalfa silage stored at 20 °C, the hemicellulose, cellulose, and acid detergent ligninin (ADL) contents decreased by 17%, 6%, and 14% compared with the control (p < 0.05), respectively. Compared with the corresponding original contents, the contents of glucose, arabinose, galactose, and fructose detected in silage treated with LP11AG after 45 days of ensiling increased by 55%, 1494%, 68%, and 5% , respectively, when stored at 40 °C. Raffinose and stachyose, originally present in alfalfa, disappeared after ensiling. In conclusion, our results suggest that LP11AG provides a substantial benefit as a silage additive.
Collapse
Affiliation(s)
- Jingui Guo
- College of Grassland Science and Technology, China Agricultural University, Beijing, 100094, China
| | - Yixiao Xie
- College of Grassland Science and Technology, China Agricultural University, Beijing, 100094, China
| | - Zhu Yu
- College of Grassland Science and Technology, China Agricultural University, Beijing, 100094, China
| | - Geng Meng
- College of Veterinary Medicine, China Agricultural University, Beijing, China
| | - Zhe Wu
- College of Grassland Science and Technology, China Agricultural University, Beijing, 100094, China.
| |
Collapse
|
3
|
Seppälä S, Wilken SE, Knop D, Solomon KV, O’Malley MA. The importance of sourcing enzymes from non-conventional fungi for metabolic engineering and biomass breakdown. Metab Eng 2017; 44:45-59. [DOI: 10.1016/j.ymben.2017.09.008] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2017] [Revised: 09/16/2017] [Accepted: 09/16/2017] [Indexed: 10/18/2022]
|
4
|
Yang WC, Hsu TC, Cheng KC, Liu JR. Expression of the Clonostachys rosea lactonohydrolase gene by Lactobacillus reuteri to increase its zearalenone-removing ability. Microb Cell Fact 2017; 16:69. [PMID: 28438205 PMCID: PMC5404306 DOI: 10.1186/s12934-017-0687-8] [Citation(s) in RCA: 37] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2017] [Accepted: 04/21/2017] [Indexed: 01/08/2023] Open
Abstract
Background Mycotoxins are secondary metabolites produced by filamentous fungi that can contaminate agricultural crops in the field as well as during harvest, transportation, processing, or storage. Zearalenone (ZEN), a non-steroidal estrogenic mycotoxin, produced by Fusarium species, has been shown to be associated with reproductive disorders in farm animals and to a lesser extent in hyperoestrogenic syndromes in humans. Thus, the decontamination of ZEN in foods and feeds is an important issue. Results In this study, the gene encoding ZHD101, a ZEN-degrading enzyme produced by Clonostachys rosea IFO 7063, was cloned into an Escherichia coli–Lactobacillus shuttle vector, pNZ3004, and the resultant plasmid pNZ-zhd101 was then introduced via electroporation into Lactobacillus reuteri Pg4, a probiotic strain isolated from the gastrointestinal tract of broilers. The transformed strain L. reuteri pNZ-zhd101 acquired the capacity to degrade ZEN. In addition, the production of recombinant ZHD101 did not affect cell growth, acid and bile salt tolerance, and had only a minor effect on the adhesion ability of L. reuteri pNZ-zhd101. Conclusions To the best of our knowledge, this is the first report of successful expression of a ZEN-degrading enzyme by intestinal lactobacilli.
Collapse
Affiliation(s)
- Wen-Chun Yang
- Graduate Institute of Food Science and Technology, National Taiwan University, No. 1, Sec. 4, Roosevelt Rd., Taipei, 10617, Taiwan
| | - Tsui-Chun Hsu
- Department of Animal Science and Technology, National Taiwan University, No. 1, Sec. 4, Roosevelt Rd., Taipei, 10617, Taiwan
| | - Kuan-Chen Cheng
- Graduate Institute of Food Science and Technology, National Taiwan University, No. 1, Sec. 4, Roosevelt Rd., Taipei, 10617, Taiwan. .,Institute of Biotechnology, National Taiwan University, No. 1, Sec. 4, Roosevelt Rd., Taipei, 10617, Taiwan. .,Department of Medical Research, China Medical University Hospital, China Medical University, No. 91, Hsueh-Shih Road, Taichung, 40402, Taiwan.
| | - Je-Ruei Liu
- Department of Animal Science and Technology, National Taiwan University, No. 1, Sec. 4, Roosevelt Rd., Taipei, 10617, Taiwan. .,Institute of Biotechnology, National Taiwan University, No. 1, Sec. 4, Roosevelt Rd., Taipei, 10617, Taiwan. .,Agricultural Biotechnology Research Center, Academia Sinica, 128 Academia Road, Section 2, Nankang, Taipei, 11529, Taiwan.
| |
Collapse
|
5
|
Gruninger RJ, Puniya AK, Callaghan TM, Edwards JE, Youssef N, Dagar SS, Fliegerova K, Griffith GW, Forster R, Tsang A, McAllister T, Elshahed MS. Anaerobic fungi (phylum Neocallimastigomycota): advances in understanding their taxonomy, life cycle, ecology, role and biotechnological potential. FEMS Microbiol Ecol 2014; 90:1-17. [PMID: 25046344 DOI: 10.1111/1574-6941.12383] [Citation(s) in RCA: 202] [Impact Index Per Article: 20.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2014] [Revised: 07/03/2014] [Accepted: 07/07/2014] [Indexed: 02/05/2023] Open
Abstract
Anaerobic fungi (phylum Neocallimastigomycota) inhabit the gastrointestinal tract of mammalian herbivores, where they play an important role in the degradation of plant material. The Neocallimastigomycota represent the earliest diverging lineage of the zoosporic fungi; however, understanding of the relationships of the different taxa (both genera and species) within this phylum is in need of revision. Issues exist with the current approaches used for their identification and classification, and recent evidence suggests the presence of several novel taxa (potential candidate genera) that remain to be characterised. The life cycle and role of anaerobic fungi has been well characterised in the rumen, but not elsewhere in the ruminant alimentary tract. Greater understanding of the 'resistant' phase(s) of their life cycle is needed, as is study of their role and significance in other herbivores. Biotechnological application of anaerobic fungi, and their highly active cellulolytic and hemi-cellulolytic enzymes, has been a rapidly increasing area of research and development in the last decade. The move towards understanding of anaerobic fungi using -omics based (genomic, transcriptomic and proteomic) approaches is starting to yield valuable insights into the unique cellular processes, evolutionary history, metabolic capabilities and adaptations that exist within the Neocallimastigomycota.
Collapse
|
6
|
Wang L, Yang Y, Cai B, Cao P, Yang M, Chen Y. Coexpression and secretion of endoglucanase and phytase genes in Lactobacillus reuteri. Int J Mol Sci 2014; 15:12842-60. [PMID: 25050780 PMCID: PMC4139877 DOI: 10.3390/ijms150712842] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2014] [Revised: 05/19/2014] [Accepted: 07/01/2014] [Indexed: 12/01/2022] Open
Abstract
A multifunctional transgenic Lactobacillus with probiotic characteristics and an ability to degrade β-glucan and phytic acid (phytate) was engineered to improve nutrient utilization, increase production performance and decrease digestive diseases in broiler chickens. The Bacillus subtilis WL001 endoglucanase gene (celW) and Aspergillus fumigatus WL002 phytase gene (phyW) mature peptide (phyWM) were cloned into an expression vector with the lactate dehydrogenase promoter of Lactobacillus casei and the secretion signal peptide of the Lactococcus lactisusp45 gene. This construct was then transformed into Lactobacillus reuteri XC1 that had been isolated from the gastrointestinal tract of broilers. Heterologous enzyme production and feed effectiveness of this genetically modified L. reuteri strain were investigated and evaluated. Sodium dodecyl sulfate polyacrylamide gel electrophoresis analysis showed that the molecular mass of phyWM and celW was approximately 48.2 and 55 kDa, respectively, consistent with their predicted molecular weights. Endoglucanase and phytase activities in the extracellular fraction of the transformed L. reuteri culture were 0.68 and 0.42 U/mL, respectively. Transformed L. reuteri improved the feed conversion ratio of broilers from 21 to 42 days of age and over the whole feeding period. However, there was no effect on body weight gain and feed intake of chicks. Transformed L. reuteri supplementation improved levels of ash, calcium and phosphorus in tibiae at day 21 and of phosphorus at day 42. In addition, populations of Escherichia coli, Veillonella spp. and Bacteroides vulgatus were decreased, while populations of Bifidobacterium genus and Lactobacillus spp. were increased in the cecum at day 21.
Collapse
Affiliation(s)
- Lei Wang
- College of Animal Science and Technology, Northwest A&F University, Yangling 712100, Shaanxi, China.
| | - Yuxin Yang
- College of Animal Science and Technology, Northwest A&F University, Yangling 712100, Shaanxi, China.
| | - Bei Cai
- College of Animal Science and Technology, Northwest A&F University, Yangling 712100, Shaanxi, China.
| | - Pinghua Cao
- College of Animal Science and Technology, Northwest A&F University, Yangling 712100, Shaanxi, China.
| | - Mingming Yang
- College of Animal Science and Technology, Northwest A&F University, Yangling 712100, Shaanxi, China.
| | - Yulin Chen
- College of Animal Science and Technology, Northwest A&F University, Yangling 712100, Shaanxi, China.
| |
Collapse
|
7
|
Hsueh HY, Yu B, Liu CT, Liu JR. Increase of the adhesion ability and display of a rumen fungal xylanase on the cell surface of Lactobacillus casei by using a listerial cell-wall-anchoring protein. JOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE 2014; 94:576-584. [PMID: 23824609 DOI: 10.1002/jsfa.6298] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/11/2013] [Revised: 06/26/2013] [Accepted: 07/03/2013] [Indexed: 06/02/2023]
Abstract
BACKGROUND Lactobacillus, which has great adhesion ability to intestinal mucosa and is able to hydrolyse plant cell walls, can be used more efficiently as a feed additive. To increase the adhesion ability and display a fungal xylanase on the cell surface of Lactobacillus casei, the Listeria monocytogenes cell-wall-anchoring protein gene, mub, was introduced into L. casei ATCC 393 cells and used as a fusion partner to display the rumen fungal xylanase XynCDBFV on the cell surface of the transformed strains. RESULTS The transformed strain L. casei pNZ-mub, which harboured mub gene, displayed recombinant Mub on its cell surface and showed greater adhesion ability to Caco-2 cells than the parental strain. The transformed strain L. casei pNZ-mub/xyn, which harboured mub-xynCDBFV fusion gene, acquired the capacity to break down oat spelt xylan and exhibited greater competition ability against the adhesion of L. monocytogenes to Caco-2 cells, in comparison with the parental strain. CONCLUSION Mub has a potential to be used as a fusion partner to display heterologous proteins on the cell surface of Lactobacillus. Moreover, this is the first report of the successful display of xylanase on the cell surface of Lactobacillus.
Collapse
Affiliation(s)
- Hsiang-Yun Hsueh
- Department of Animal Science and Technology, National Taiwan University, Taipei, Taiwan
| | | | | | | |
Collapse
|
8
|
Establishment of a simple Lactobacillus plantarum cell consortium for cellulase-xylanase synergistic interactions. Appl Environ Microbiol 2013; 79:5242-9. [PMID: 23811500 DOI: 10.1128/aem.01211-13] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Lactobacillus plantarum is an attractive candidate for bioprocessing of lignocellulosic biomass due to its high metabolic variability, including its ability to ferment both pentoses and hexoses, as well as its high acid tolerance, a quality often utilized in industrial processes. This bacterium grows naturally on biomass; however, it lacks the inherent ability to deconstruct lignocellulosic substrates. As a first step toward engineering lignocellulose-converting lactobacilli, we have introduced genes coding for a GH6 cellulase and a GH11 xylanase from a highly active cellulolytic bacterium into L. plantarum. For this purpose, we employed the recently developed pSIP vectors for efficient secretion of heterologous proteins. Both enzymes were secreted by L. plantarum at levels estimated at 0.33 nM and 3.3 nM, for the cellulase and xylanase, respectively, in culture at an optical density at 600 nm (OD600) of 1. Transformed cells demonstrated the ability to degrade individually either cellulose or xylan and wheat straw. When mixed together to form a two-strain cell-based consortium secreting both cellulase and xylanase, they exhibited synergistic activity in the overall release of soluble sugar from wheat straw. This result paves the way toward metabolic harnessing of L. plantarum for novel biorefining applications, such as production of ethanol and polylactic acid directly from plant biomass.
Collapse
|
9
|
Purification, characterization, and heterologous expression of a thermostable β-1,3-1,4-glucanase from Bacillus altitudinis YC-9. Appl Biochem Biotechnol 2013; 169:960-75. [PMID: 23292246 DOI: 10.1007/s12010-012-0064-3] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2012] [Accepted: 12/26/2012] [Indexed: 10/27/2022]
Abstract
Purification, characterization, gene cloning, and heterologous expression in Escherichia coli of a thermostable β-1,3-1,4-glucanase from Bacillus altitudinis YC-9 have been investigated in this paper. The donor strain B. altitudinis YC-9 was isolated from spring silt. The native enzyme was purified by ammonium sulfate precipitation, diethylaminoethyl-cellulose anion exchange chromatography, and Sephadex G-100 gel filtration. The purified β-1,3-1,4-glucanase was observed to be stable at 60 °C and retain more than 90% activity when incubated for 2 h at 60 °C and remain about 75% and 44% activity after incubating at 70 °C and 80 °C for 10 min, respectively. Acidity and temperature optimal for this enzyme was pH 6 and 65 °C. The open reading frame of the enzyme gene was measured to be 732 bp encoding 243 amino acids, with a predicted molecular weight of 27.47 kDa. The gene sequence of β-1,3-1,4-glucanase showed a homology of 98% with that of Bacillus licheniformis. After being expressed in E. coli BL21, active recombinant enzyme was detected both in the supernatants of the culture and the cell lysate, with the activity of 102.7 and 216.7 U/mL, respectively. The supernatants of the culture were used to purify the recombinant enzyme. The purified recombinant enzyme was characterized to show almost the same properties to the wild enzyme, except that the specific activity of the recombinant enzyme reached 5392.7 U/mg, which was higher than those ever reported β-1,3-1,4-glucanase from Bacillus strains. The thermal stability and high activity make this enzyme broad prospect for industry application. This is the first report on β-1,3-1,4-glucanase produced by B. altitudinis.
Collapse
|
10
|
Li W, Yang MM, Zhang GQ, He WL, Li YX, Chen YL. Electrotransformation and Expression of Cellulase Genes in Wild-Type Lactobacillus reuteri. J Mol Microbiol Biotechnol 2012; 22:228-34. [DOI: 10.1159/000341906] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
|
11
|
Characterization of a bifunctional xylanase/endoglucanase from yak rumen microorganisms. Appl Microbiol Biotechnol 2011; 90:1933-42. [DOI: 10.1007/s00253-011-3182-x] [Citation(s) in RCA: 55] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2011] [Revised: 02/01/2011] [Accepted: 02/02/2011] [Indexed: 11/25/2022]
|
12
|
Huang SJ, Chen MJ, Yueh PY, Yu B, Zhao X, Liu JR. Display of Fibrobacter succinogenes β-glucanase on the cell surface of Lactobacillus reuteri. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2011; 59:1744-1751. [PMID: 21302894 DOI: 10.1021/jf104266x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
The aim of this study was to display a rumen bacterial β-glucanase on the cell surface of a probiotic Lactobacillus reuteri strain. The β-glucan degrading ability and the adhesion capability of the genetically modified strain were evaluated. The β-glucanase (Glu) from Fibrobacter succinogenes was fused to the C-terminus of collagen-binding protein (Cnb) from L. reuteri and then expressed by L. reuteri Pg4 as a recombinant Cnb-Glu-His(6) fusion protein. Confocal immunofluorescence microscopy and flow cytometric analysis of the transformed strain L. reuteri pNZ-cnb/glu demonstrated that Cnb-Glu-His(6) fusion protein was displayed on its cell surface. In addition, L. reuteri pNZ-cnb/glu acquired the capacity to break down barley β-glucan and showed higher adhesion capability, in comparison with the parental strain L. reuteri Pg4. To the best of the authors' knowledge, this is the first report of successful display of fibrolytic enzymes on the cell surface of intestinal lactobacilli.
Collapse
Affiliation(s)
- Shu-Jung Huang
- Department of Animal Science and Technology and Institute of Biotechnology, National Taiwan University , Taipei, Taiwan
| | | | | | | | | | | |
Collapse
|
13
|
la Grange DC, den Haan R, van Zyl WH. Engineering cellulolytic ability into bioprocessing organisms. Appl Microbiol Biotechnol 2010; 87:1195-208. [DOI: 10.1007/s00253-010-2660-x] [Citation(s) in RCA: 83] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2010] [Revised: 05/02/2010] [Accepted: 05/02/2010] [Indexed: 10/19/2022]
|
14
|
Huang H, Yang P, Luo H, Tang H, Shao N, Yuan T, Wang Y, Bai Y, Yao B. High-level expression of a truncated 1,3-1,4-beta-D-glucanase from Fibrobacter succinogenes in Pichia pastoris by optimization of codons and fermentation. Appl Microbiol Biotechnol 2007; 78:95-103. [PMID: 18080120 DOI: 10.1007/s00253-007-1290-4] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2007] [Revised: 11/14/2007] [Accepted: 11/15/2007] [Indexed: 11/25/2022]
Abstract
1,3-1,4-beta-D-glucanase is an important endoglycosidase in the brewing and animal feed industries. To achieve high-level expression of recombinant glucanase in Pichia pastoris, we designed sequences encoding the alpha-factor signal peptide from Saccharomyces cerevisiae and the truncated 1,3-1,4-beta-D-glucanase from Fibrobacter succinogenes as a whole. The codons encoding the 52 amino acids of the signal peptide and 106 residues of the glucanase protein were optimized for expression in P. pastoris; 189 nucleotides were changed. The G + C content was adjusted to 48-49%, and AT-rich stretches were eliminated to avoid premature termination. The messenger ribonucleic acid secondary structure near the AUG start codon was also adjusted to ensure efficient translation; the resulting glucanase production was twofold higher compared with that achieved with gene structure optimization alone. We also propose a new fermentation strategy for the induction phase, in which 5/95% glycerol/methanol mixed feed was used in days 1-3 and 100% methanol was used on days 4-6. By comparison with methanol feed and glycerol/methanol-mixed feed alone, the yield of recombinant glucanase increased by 38.5 and 16.5%, respectively. The expressed optimized recombinant 1,3-1,4-beta-D-glucanase constituted approximately 90% of the total secreted protein, reaching up to 3 g l(-1) in the medium.
Collapse
Affiliation(s)
- Huoqing Huang
- Department of Microbial Engineering, Feed Research Institute, Chinese Academy of Agricultural Sciences, no. 12 Zhongguancun South Street, Beijing, 100081, People's Republic of China
| | | | | | | | | | | | | | | | | |
Collapse
|