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de Souza MF, da Silva Bon EP, da Silva AS. Production of cellulases and β-glucosidases by Trichoderma reesei Rut C30 using steam-pretreated sugarcane bagasse: an integrated approach for onsite enzyme production. BRAZILIAN JOURNAL OF CHEMICAL ENGINEERING 2021. [DOI: 10.1007/s43153-021-00114-5] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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Zheng F, Yang R, Cao Y, Zhang W, Lv X, Meng X, Zhong Y, Chen G, Zhou Q, Liu W. Engineering Trichoderma reesei for Hyperproduction of Cellulases on Glucose to Efficiently Saccharify Pretreated Corncobs. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2020; 68:12671-12682. [PMID: 33140639 DOI: 10.1021/acs.jafc.0c04663] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/15/2023]
Abstract
The filamentous fungus Trichoderma reesei (teleomorph Hypocrea jecorina) is widely used as a cellulase producer in the industry. Herein, we describe the rational engineering of the publicly available T. reesei QM9414 strain to achieve a remarkable high-level production of cellulase on glucose. Overexpression of the key cellulase regulator XYR1 by the copper-repressible promoter Ptcu1 was first implemented to achieve a full cellulase production in the context of catabolite repression (CCR) while eliminating the requirement of inducing sugars for enzyme production. The T. reesei bgl1 gene was further overexpressed to compensate for its low β-glucosidase activity on glucose. This overexpression resulted in a 102% increase in FPase activity compared with the CCR-released RUT-C30 strain cultured on Avicel. Moreover, the saccharification efficiency toward pretreated corncob residues by crude enzymes from the engineered strain on glucose increased by 85% compared with that treated by enzymes from RUT-C30 cultivated on Avicel. The engineered T. reesei strain thus shows great potential as a viable alternative to deliver commercial cellulases after further optimization for efficient saccharification of agricultural waste.
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Affiliation(s)
- Fanglin Zheng
- State Key Laboratory of Microbial Technology, Institute of Microbial Technology, Shandong University, No.72 Binhai Road, Qingdao, Shandong 266237, P. R. China
| | - Renfei Yang
- State Key Laboratory of Microbial Technology, Institute of Microbial Technology, Shandong University, No.72 Binhai Road, Qingdao, Shandong 266237, P. R. China
| | - Yanli Cao
- State Key Laboratory of Microbial Technology, Institute of Microbial Technology, Shandong University, No.72 Binhai Road, Qingdao, Shandong 266237, P. R. China
| | - Weixin Zhang
- State Key Laboratory of Microbial Technology, Institute of Microbial Technology, Shandong University, No.72 Binhai Road, Qingdao, Shandong 266237, P. R. China
| | - Xinxing Lv
- State Key Laboratory of Microbial Technology, Institute of Microbial Technology, Shandong University, No.72 Binhai Road, Qingdao, Shandong 266237, P. R. China
| | - Xiangfeng Meng
- State Key Laboratory of Microbial Technology, Institute of Microbial Technology, Shandong University, No.72 Binhai Road, Qingdao, Shandong 266237, P. R. China
| | - Yaohua Zhong
- State Key Laboratory of Microbial Technology, Institute of Microbial Technology, Shandong University, No.72 Binhai Road, Qingdao, Shandong 266237, P. R. China
| | - Guanjun Chen
- State Key Laboratory of Microbial Technology, Institute of Microbial Technology, Shandong University, No.72 Binhai Road, Qingdao, Shandong 266237, P. R. China
| | - Qingxin Zhou
- Shandong Academy of Agricultural Sciences/Key Laboratory of Agro-Products Processing Technology of Shandong Province/Key Laboratory of Novel Food Resources Processing, Ministry of Agriculture and Rural Affairs, Institute of Agro-Food Science and Technology, No.202 Gongye North Road, Jinan 250100, P. R. China
- College of Life Science, Shandong Normal University, No.88 Wenhua East Road, Jinan 250014, P. R. China
| | - Weifeng Liu
- State Key Laboratory of Microbial Technology, Institute of Microbial Technology, Shandong University, No.72 Binhai Road, Qingdao, Shandong 266237, P. R. China
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Hooker CA, Hillman ET, Overton JC, Ortiz-Velez A, Schacht M, Hunnicutt A, Mosier NS, Solomon KV. Hydrolysis of untreated lignocellulosic feedstock is independent of S-lignin composition in newly classified anaerobic fungal isolate, Piromyces sp. UH3-1. BIOTECHNOLOGY FOR BIOFUELS 2018; 11:293. [PMID: 30386430 PMCID: PMC6203967 DOI: 10.1186/s13068-018-1292-8] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/21/2018] [Accepted: 10/15/2018] [Indexed: 05/26/2023]
Abstract
BACKGROUND Plant biomass is an abundant but underused feedstock for bioenergy production due to its complex and variable composition, which resists breakdown into fermentable sugars. These feedstocks, however, are routinely degraded by many uncommercialized microbes such as anaerobic gut fungi. These gut fungi express a broad range of carbohydrate active enzymes and are native to the digestive tracts of ruminants and hindgut fermenters. In this study, we examine gut fungal performance on these substrates as a function of composition, and the ability of this isolate to degrade inhibitory high syringyl lignin-containing forestry residues. RESULTS We isolated a novel fungal specimen from a donkey in Independence, Indiana, United States. Phylogenetic analysis of the Internal Transcribed Spacer 1 sequence classified the isolate as a member of the genus Piromyces within the phylum Neocallimastigomycota (Piromyces sp. UH3-1, strain UH3-1). The isolate penetrates the substrate with an extensive rhizomycelial network and secretes many cellulose-binding enzymes, which are active on various components of lignocellulose. These activities enable the fungus to hydrolyze at least 58% of the glucan and 28% of the available xylan in untreated corn stover within 168 h and support growth on crude agricultural residues, food waste, and energy crops. Importantly, UH3-1 hydrolyzes high syringyl lignin-containing poplar that is inhibitory to many fungi with efficiencies equal to that of low syringyl lignin-containing poplar with no reduction in fungal growth. This behavior is correlated with slight remodeling of the fungal secretome whose composition adapts with substrate to express an enzyme cocktail optimized to degrade the available biomass. CONCLUSIONS Piromyces sp. UH3-1, a newly isolated anaerobic gut fungus, grows on diverse untreated substrates through production of a broad range of carbohydrate active enzymes that are robust to variations in substrate composition. Additionally, UH3-1 and potentially other anaerobic fungi are resistant to inhibitory lignin composition possibly due to changes in enzyme secretion with substrate. Thus, anaerobic fungi are an attractive platform for the production of enzymes that efficiently use mixed feedstocks of variable composition for second generation biofuels. More importantly, our work suggests that the study of anaerobic fungi may reveal naturally evolved strategies to circumvent common hydrolytic inhibitors that hinder biomass usage.
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Affiliation(s)
- Casey A. Hooker
- Department of Agricultural and Biological Engineering, Purdue University, 225 South University Street, West Lafayette, IN 47907-2093 USA
- Laboratory of Renewable Resources Engineering (LORRE), Purdue University, 500 Central Drive, West Lafayette, IN 47907-2022 USA
| | - Ethan T. Hillman
- Department of Agricultural and Biological Engineering, Purdue University, 225 South University Street, West Lafayette, IN 47907-2093 USA
- Purdue University Interdisciplinary Life Sciences (PULSe) Program, Purdue University, 155 South Grant Street, West Lafayette, IN 47907-2114 USA
| | - Jonathan C. Overton
- Department of Agricultural and Biological Engineering, Purdue University, 225 South University Street, West Lafayette, IN 47907-2093 USA
- Laboratory of Renewable Resources Engineering (LORRE), Purdue University, 500 Central Drive, West Lafayette, IN 47907-2022 USA
| | - Adrian Ortiz-Velez
- Department of Agricultural and Biological Engineering, Purdue University, 225 South University Street, West Lafayette, IN 47907-2093 USA
| | - Makayla Schacht
- Department of Biological Sciences, Purdue University, 915 West State Street, West Lafayette, IN 47907-2054 USA
| | - Abigail Hunnicutt
- Department of Agricultural and Biological Engineering, Purdue University, 225 South University Street, West Lafayette, IN 47907-2093 USA
| | - Nathan S. Mosier
- Department of Agricultural and Biological Engineering, Purdue University, 225 South University Street, West Lafayette, IN 47907-2093 USA
- Laboratory of Renewable Resources Engineering (LORRE), Purdue University, 500 Central Drive, West Lafayette, IN 47907-2022 USA
| | - Kevin V. Solomon
- Department of Agricultural and Biological Engineering, Purdue University, 225 South University Street, West Lafayette, IN 47907-2093 USA
- Laboratory of Renewable Resources Engineering (LORRE), Purdue University, 500 Central Drive, West Lafayette, IN 47907-2022 USA
- Purdue University Interdisciplinary Life Sciences (PULSe) Program, Purdue University, 155 South Grant Street, West Lafayette, IN 47907-2114 USA
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Wang B, Jiang L, Bai H, Yong Q, Yu S. Regular enzyme recovery enhances cellulase production by Trichoderma reesei in fed-batch culture. Biotechnol Lett 2017; 39:1493-1498. [PMID: 28612265 DOI: 10.1007/s10529-017-2379-1] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2017] [Accepted: 06/07/2017] [Indexed: 12/01/2022]
Abstract
OBJECTIVE To protect the enzymes during fed-batch cellulase production by means of partial enzyme recovery at regular intervals. RESULTS Extracellular enzymes were partially recovered at the intervals of 1, 2, or 3 days. Mycelia were also removed to avoid contamination. Increases in the total harvested cellulase (24-62%) and β-glucosidase (22-76%) were achieved. In fermentor cultivation when the enzymes were recovered every day with 15% culture broth. The total harvested cellulase and β-glucosidase activity increased by 43 and 58%, respectively, with fungal cell concentration maintained at 3.5-4.5 g l-1. CONCLUSION Enzyme recovery at regular intervals during fed-batch cellulase cultivation could protect the enzyme in the culture broth and enhance the enzyme production when the fungal cell concentration is maintained in a reasonable range.
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Affiliation(s)
- Bucheng Wang
- Key Laboratory of Forest Genetics & Biotechnology, Ministry of Education, Nanjing Forestry University, Nanjing, 210037, China
| | - Lu Jiang
- Key Laboratory of Forest Genetics & Biotechnology, Ministry of Education, Nanjing Forestry University, Nanjing, 210037, China
| | - Hechao Bai
- Key Laboratory of Forest Genetics & Biotechnology, Ministry of Education, Nanjing Forestry University, Nanjing, 210037, China
| | - Qiang Yong
- Key Laboratory of Forest Genetics & Biotechnology, Ministry of Education, Nanjing Forestry University, Nanjing, 210037, China
| | - Shiyuan Yu
- Key Laboratory of Forest Genetics & Biotechnology, Ministry of Education, Nanjing Forestry University, Nanjing, 210037, China.
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Ellilä S, Fonseca L, Uchima C, Cota J, Goldman GH, Saloheimo M, Sacon V, Siika-aho M. Development of a low-cost cellulase production process using Trichoderma reesei for Brazilian biorefineries. BIOTECHNOLOGY FOR BIOFUELS 2017; 10:30. [PMID: 28184245 PMCID: PMC5289010 DOI: 10.1186/s13068-017-0717-0] [Citation(s) in RCA: 85] [Impact Index Per Article: 12.1] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/24/2016] [Accepted: 01/25/2017] [Indexed: 05/21/2023]
Abstract
BACKGROUND During the past few years, the first industrial-scale cellulosic ethanol plants have been inaugurated. Although the performance of the commercial cellulase enzymes used in this process has greatly improved over the past decade, cellulases still represent a very significant operational cost. Depending on the region, transport of cellulases from a central production facility to a biorefinery may significantly add to enzyme cost. The aim of the present study was to develop a simple, cost-efficient cellulase production process that could be employed locally at a Brazilian sugarcane biorefinery. RESULTS Our work focused on two main topics: growth medium formulation and strain improvement. We evaluated several Brazilian low-cost industrial residues for their potential in cellulase production. Among the solid residues evaluated, soybean hulls were found to display clearly the most desirable characteristics. We engineered a Trichoderma reesei strain to secrete cellulase in the presence of repressing sugars, enabling the use of sugarcane molasses as an additional carbon source. In addition, we added a heterologous β-glucosidase to improve the performance of the produced enzymes in hydrolysis. Finally, the addition of an invertase gene from Aspegillus niger into our strain allowed it to consume sucrose from sugarcane molasses directly. Preliminary cost analysis showed that the overall process can provide for very low-cost enzyme with good hydrolysis performance on industrially pre-treated sugarcane straw. CONCLUSIONS In this study, we showed that with relatively few genetic modifications and the right growth medium it is possible to produce considerable amounts of well-performing cellulase at very low cost in Brazil using T. reesei. With further enhancements and optimization, such a system could provide a viable alternative to delivered commercial cellulases.
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Affiliation(s)
- Simo Ellilä
- VTT Brasil Ltda., Barueri, Sao Paulo Brazil
- VTT Technical Research Centre of Finland, Tietotie 2, 02044 Espoo, Finland
| | | | | | - Junio Cota
- VTT Brasil Ltda., Barueri, Sao Paulo Brazil
- Instituto de Ciências Agrárias, Universidade Federal de Minas Gerais (UFMG), Montes Claros, MG Brazil
| | - Gustavo Henrique Goldman
- Faculdade de Ciências Farmacêuticas de Ribeirão Preto, Universidade de Sao Paulo, Ribeirão Preto, SP Brazil
| | - Markku Saloheimo
- VTT Technical Research Centre of Finland, Tietotie 2, 02044 Espoo, Finland
| | - Vera Sacon
- VTT Brasil Ltda., Barueri, Sao Paulo Brazil
| | - Matti Siika-aho
- VTT Technical Research Centre of Finland, Tietotie 2, 02044 Espoo, Finland
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Okeke BC, Hall RW, Nanjundaswamy A, Thomson MS, Deravi Y, Sawyer L, Prescott A. Selection and molecular characterization of cellulolytic–xylanolytic fungi from surface soil-biomass mixtures from Black Belt sites. Microbiol Res 2015; 175:24-33. [DOI: 10.1016/j.micres.2015.03.001] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2014] [Revised: 02/25/2015] [Accepted: 03/02/2015] [Indexed: 10/23/2022]
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Cellulolytic and xylanolytic potential of high β-glucosidase-producing Trichoderma from decaying biomass. Appl Biochem Biotechnol 2014; 174:1581-1598. [PMID: 25129039 DOI: 10.1007/s12010-014-1121-x] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2014] [Accepted: 07/23/2014] [Indexed: 11/25/2022]
Abstract
Availability, cost, and efficiency of microbial enzymes for lignocellulose bioconversion are central to sustainable biomass ethanol technology. Fungi enriched from decaying biomass and surface soil mixture displayed an array of strong cellulolytic and xylanolytic activities. Strains SG2 and SG4 produced a promising array of cellulolytic and xylanolytic enzymes including β-glucosidase, usually low in cultures of Trichoderma species. Nucleotide sequence analysis of internal transcribed spacer 2 (ITS2) region of rRNA gene revealed that strains SG2 and SG4 are closely related to Trichoderma inhamatum, Trichoderma piluliferum, and Trichoderma aureoviride. Trichoderma sp. SG2 crude culture supernatant correspondingly displayed as much as 9.84 ± 1.12, 48.02 ± 2.53, and 30.10 ± 1.11 units mL(-1) of cellulase, xylanase, and β-glucosidase in 30 min assay. Ten times dilution of culture supernatant of strain SG2 revealed that total activities were about 5.34, 8.45, and 2.05 orders of magnitude higher than observed in crude culture filtrate for cellulase, xylanase, and β-glucosidase, respectively, indicating that more enzymes are present to contact with substrates in biomass saccharification. In parallel experiments, Trichoderma species SG2 and SG4 produced more β-glucosidase than the industrial strain Trichoderma reesei RUT-C30. Results indicate that strains SG2 and SG4 have potential for low cost in-house production of primary lignocellulose-hydrolyzing enzymes for production of biomass saccharides and biofuel in the field.
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Chu Q, Li X, Xu Y, Wang Z, Huang J, Yu S, Yong Q. Functional cello-oligosaccharides production from the corncob residues of xylo-oligosaccharides manufacture. Process Biochem 2014. [DOI: 10.1016/j.procbio.2014.05.007] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
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Optimisation of Cellulase Production by Penicillium funiculosum in a Stirred Tank Bioreactor Using Multivariate Response Surface Analysis. Enzyme Res 2014; 2014:703291. [PMID: 25057412 PMCID: PMC4099281 DOI: 10.1155/2014/703291] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2014] [Revised: 06/10/2014] [Accepted: 06/11/2014] [Indexed: 11/18/2022] Open
Abstract
Increasing interest in the production of second-generation ethanol necessitates the low-cost production of enzymes from the cellulolytic complex (endoglucanases, exoglucanases, and β-glucosidases), which act synergistically in cellulose breakdown. The present work aimed to optimise a bioprocess to produce these biocatalysts from the fungus Penicillium funiculosum ATCC11797. A statistical full factorial design (FFD) was employed to determine the optimal conditions for cellulase production. The optimal composition of culture media using Avicel (10 g·L−1) as carbon source was determined to include urea (1.2 g·L−1), yeast extract (1.0 g·L−1), KH2PO4 (6.0 g·L−1), and MgSO4·7H2O (1.2 g·L−1). The growth process was performed in batches in a bioreactor. Using a different FFD strategy, the optimised bioreactor operational conditions of an agitation speed of 220 rpm and aeration rate of 0.6 vvm allowed the obtainment of an enzyme pool with activities of 508 U·L−1 for FPase, 9,204 U·L−1 for endoglucanase, and 2,395 U·L−1 for β-glucosidase. The sequential optimisation strategy was effective and afforded increased cellulase production in the order from 3.6 to 9.5 times higher than production using nonoptimised conditions.
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Isolation, identification and characterization of a novel high level β-glucosidase-producing Lichtheimia ramosa strain. BIOCATALYSIS AND AGRICULTURAL BIOTECHNOLOGY 2013. [DOI: 10.1016/j.bcab.2013.06.006] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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Gray BN, Yang H, Ahner BA, Hanson MR. An efficient downstream box fusion allows high-level accumulation of active bacterial beta-glucosidase in tobacco chloroplasts. PLANT MOLECULAR BIOLOGY 2011; 76:345-55. [PMID: 21279422 DOI: 10.1007/s11103-011-9743-7] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/05/2010] [Accepted: 01/17/2011] [Indexed: 05/03/2023]
Abstract
Production of enzymes for lignocellulose hydrolysis in planta has been proposed as a lower-cost alternative to microbial production, with plastid transformation as a preferred method due to high foreign protein yields. An important regulator of chloroplast protein production is the downstream box (DB) region, located immediately downstream of the start codon. Protein accumulation can vary over several orders of magnitude by altering the DB region. Experiments in bacteria have suggested that these differences in protein accumulation may result from changes in translation efficiency, though the precise mechanism of DB function is not known. In this study, three DB regions were fused to the bglC ORF encoding a β-glucosidase from the thermophilic bacterium Thermobifida fusca and inserted into the tobacco (Nicotiana tabacum) plastid genome. More than a two order of magnitude of difference in BglC protein accumulation was observed, dependent on the identity of the DB fusion. Differential transcript accumulation explained some the observed differences in protein accumulation, but in addition, less 3' degradation of bglC transcripts was observed in transgenic plants that accumulated the most BglC enzyme. Chloroplast-produced BglC was active against both pure cellobiose and against tobacco lignocellulose. These experiments demonstrate the potential utility of transplastomic plants as a vehicle for heterologous β-glucosidase production for the cellulosic ethanol industry.
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Affiliation(s)
- Benjamin N Gray
- Department of Biological and Environmental Engineering, Cornell University, 202 Riley Robb, Ithaca, NY 14853, USA
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Production of Cell Membrane-Bound α- and β-Glucosidase by Lactobacillus acidophilus. FOOD BIOPROCESS TECH 2010. [DOI: 10.1007/s11947-010-0417-2] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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Trichoderma harzianum IOC-4038: A Promising Strain for the Production of a Cellulolytic Complex with Significant β-Glucosidase Activity from Sugarcane Bagasse Cellulignin. Appl Biochem Biotechnol 2010; 162:2111-22. [DOI: 10.1007/s12010-010-8986-0] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2010] [Accepted: 04/26/2010] [Indexed: 10/19/2022]
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Chen M, Qin Y, Liu Z, Liu K, Wang F, Qu Y. Isolation and characterization of a β-glucosidase from Penicillium decumbens and improving hydrolysis of corncob residue by using it as cellulase supplementation. Enzyme Microb Technol 2010; 46:444-9. [DOI: 10.1016/j.enzmictec.2010.01.008] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2009] [Revised: 12/11/2009] [Accepted: 01/28/2010] [Indexed: 11/25/2022]
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Characterisation of specific activities and hydrolytic properties of cell-wall-degrading enzymes produced by Trichoderma reesei Rut C30 on different carbon sources. Appl Biochem Biotechnol 2009; 161:347-64. [PMID: 19898963 DOI: 10.1007/s12010-009-8824-4] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2009] [Accepted: 10/13/2009] [Indexed: 10/20/2022]
Abstract
Conversion of lignocellulosic substrates is limited by several factors, in terms of both the enzymes and the substrates. Better understanding of the hydrolysis mechanisms and the factors determining their performance is crucial for commercial lignocelluloses-based processes. Enzymes produced on various carbon sources (Solka Floc 200, lactose and steam-pre-treated corn stover) by Trichoderma reesei Rut C30 were characterised by their enzyme profile and hydrolytic performance. The results showed that there was a clear correlation between the secreted amount of xylanase and mannanase enzymes and that their production was induced by the presence of xylan in the carbon source. Co-secretion of alpha-arabinosidase and alpha-galactosidase was also observed. Secretion of beta-glucosidase was found to be clearly dependent on the composition of the carbon source, and in the case of lactose, 2-fold higher specific activity was observed compared to Solka Floc and steam-pre-treated corn stover. Hydrolysis experiments showed a clear connection between glucan and xylan conversion and highlighted the importance of beta-glucosidase and xylanase activities. When hydrolysis was performed using additional purified beta-glucosidase and xylanase, the addition of beta-glucosidase was found to significantly improve both the xylan and glucan conversion.
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