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Wang Y, Zhang Y, Cui Q, Feng Y, Xuan J. Composition of Lignocellulose Hydrolysate in Different Biorefinery Strategies: Nutrients and Inhibitors. Molecules 2024; 29:2275. [PMID: 38792135 PMCID: PMC11123716 DOI: 10.3390/molecules29102275] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2024] [Revised: 05/06/2024] [Accepted: 05/09/2024] [Indexed: 05/26/2024] Open
Abstract
The hydrolysis and biotransformation of lignocellulose, i.e., biorefinery, can provide human beings with biofuels, bio-based chemicals, and materials, and is an important technology to solve the fossil energy crisis and promote global sustainable development. Biorefinery involves steps such as pretreatment, saccharification, and fermentation, and researchers have developed a variety of biorefinery strategies to optimize the process and reduce process costs in recent years. Lignocellulosic hydrolysates are platforms that connect the saccharification process and downstream fermentation. The hydrolysate composition is closely related to biomass raw materials, the pretreatment process, and the choice of biorefining strategies, and provides not only nutrients but also possible inhibitors for downstream fermentation. In this review, we summarized the effects of each stage of lignocellulosic biorefinery on nutrients and possible inhibitors, analyzed the huge differences in nutrient retention and inhibitor generation among various biorefinery strategies, and emphasized that all steps in lignocellulose biorefinery need to be considered comprehensively to achieve maximum nutrient retention and optimal control of inhibitors at low cost, to provide a reference for the development of biomass energy and chemicals.
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Affiliation(s)
- Yilan Wang
- Department of Bioscience and Bioengineering, School of Chemistry and Biological Engineering, University of Science and Technology Beijing, 30 Xueyuan Road, Beijing 100083, China
- CAS Key Laboratory of Biofuels, Shandong Provincial Key Laboratory of Synthetic Biology, Shandong Engineering Laboratory of Single Cell Oil, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, 189 Songling Road, Qingdao 266101, China
| | - Yuedong Zhang
- CAS Key Laboratory of Biofuels, Shandong Provincial Key Laboratory of Synthetic Biology, Shandong Engineering Laboratory of Single Cell Oil, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, 189 Songling Road, Qingdao 266101, China
- Shandong Energy Institute, 189 Songling Road, Qingdao 266101, China
- Qingdao New Energy Shandong Laboratory, 189 Songling Road, Qingdao 266101, China
| | - Qiu Cui
- CAS Key Laboratory of Biofuels, Shandong Provincial Key Laboratory of Synthetic Biology, Shandong Engineering Laboratory of Single Cell Oil, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, 189 Songling Road, Qingdao 266101, China
- State Key Laboratory of Microbial Technology, Shandong University, Qingdao 266237, China
| | - Yingang Feng
- CAS Key Laboratory of Biofuels, Shandong Provincial Key Laboratory of Synthetic Biology, Shandong Engineering Laboratory of Single Cell Oil, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, 189 Songling Road, Qingdao 266101, China
- Shandong Energy Institute, 189 Songling Road, Qingdao 266101, China
- Qingdao New Energy Shandong Laboratory, 189 Songling Road, Qingdao 266101, China
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - Jinsong Xuan
- Department of Bioscience and Bioengineering, School of Chemistry and Biological Engineering, University of Science and Technology Beijing, 30 Xueyuan Road, Beijing 100083, China
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Sun C, Meng X, Sun F, Zhang J, Tu M, Chang JS, Reungsang A, Xia A, Ragauskas AJ. Advances and perspectives on mass transfer and enzymatic hydrolysis in the enzyme-mediated lignocellulosic biorefinery: A review. Biotechnol Adv 2023; 62:108059. [PMID: 36402253 DOI: 10.1016/j.biotechadv.2022.108059] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2022] [Revised: 11/04/2022] [Accepted: 11/13/2022] [Indexed: 11/18/2022]
Abstract
Enzymatic hydrolysis is a critical process for the cellulase-mediated lignocellulosic biorefinery to produce sugar syrups that can be converted into a whole range of biofuels and biochemicals. Such a process operating at high-solid loadings (i.e., scarcely any free water or roughly ≥ 15% solids, w/w) is considered more economically feasible, as it can generate a high sugar concentration at low operation and capital costs. However, this approach remains restricted and incurs "high-solid effects", ultimately causing the lower hydrolysis yields with increasing solid loadings. The lack of available water leads to a highly viscous system with impaired mixing that exhibits strong transfer resistance and reaction limitation imposed on enzyme action. Evidently, high-solid enzymatic hydrolysis involves multi-scale mass transfer and multi-phase enzyme reaction, and thus requires a synergistic perspective of transfer and biotransformation to assess the interactions among water, biomass components, and cellulase enzymes. Porous particle characteristics of biomass and its interface properties determine the water form and distribution state surrounding the particles, which are summarized in this review aiming to identify the water-driven multi-scale/multi-phase bioprocesses. Further aided by the cognition of rheological behavior of biomass slurry, solute transfer theories, and enzyme kinetics, the coupling effects of flow-transfer-reaction are revealed under high-solid conditions. Based on the above basic features, this review lucidly explains the causes of high-solid hydrolysis hindrances, highlights the mismatched issues between transfer and reaction, and more importantly, presents the advanced strategies for transfer and reaction enhancements from the viewpoint of process optimization, reactor design, as well as enzyme/auxiliary additive customization.
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Affiliation(s)
- Chihe Sun
- Key Laboratory of Industrial Biotechnology of MOE, School of Biotechnology, Jiangnan University, Wuxi 214122, China
| | - Xianzhi Meng
- Department of Chemical & Biomolecular Engineering, University of Tennessee, Knoxville, TN 37996, USA
| | - Fubao Sun
- Key Laboratory of Industrial Biotechnology of MOE, School of Biotechnology, Jiangnan University, Wuxi 214122, China.
| | - Junhua Zhang
- Jiangsu Co-Innovation Center of Efficient Processing and Utilization of Forest Resources, College of Chemical Engineering, Nanjing Forestry University, 159 Longpan Road, Nanjing 210037, China
| | - Maobing Tu
- Department of Chemical and Environmental Engineering, University of Cincinnati, Cincinnati, OH 45221, USA
| | - Jo-Shu Chang
- Department of Chemical and Materials Engineering, Tunghai University, Taichung 407, Taiwan
| | - Alissara Reungsang
- Department of Biotechnology, Faculty of Technology, Khon Kaen University, Khon Kaen 40002, Thailand
| | - Ao Xia
- Key Laboratory of Low-grade Energy Utilization Technologies and Systems, Chongqing University, Ministry of Education, Chongqing 400044, China
| | - Arthur J Ragauskas
- Department of Chemical & Biomolecular Engineering, University of Tennessee, Knoxville, TN 37996, USA; Center for Renewable Carbon, Department of Forestry, Wildlife and Fisheries, The University of Tennessee, Knoxville, TN 37996, USA; Joint Institute of Biological Sciences, Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA.
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Madadi M, Song G, Sun F, Sun C, Xia C, Zhang E, Karimi K, Tu M. Positive role of non-catalytic proteins on mitigating inhibitory effects of lignin and enhancing cellulase activity in enzymatic hydrolysis: Application, mechanism, and prospective. ENVIRONMENTAL RESEARCH 2022; 215:114291. [PMID: 36103929 DOI: 10.1016/j.envres.2022.114291] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/25/2022] [Revised: 08/18/2022] [Accepted: 09/04/2022] [Indexed: 06/15/2023]
Abstract
Fermentable sugar production from lignocellulosic biomass has received considerable attention and has been dramatic progress recently. However, due to low enzymatic hydrolysis (EH) yields and rates, a high dosage of the costly enzyme is required, which is a bottleneck for commercial applications. Over the last decades, various strategies have been developed to reduce cellulase enzyme costs. The progress of the non-catalytic additive proteins in mitigating inhibition in EH is discussed in detail in this review. The low efficiency of EH is mostly due to soluble lignin compounds, insoluble lignin, and harsh thermal and mechanical conditions of the EH process. Adding non-catalytic proteins into the EH is considered a simple and efficient approach to boost hydrolysis yield. This review discussed the multiple mechanical steps involved in the EH process. The effect of physicochemical properties of modified lignin on EH and its interaction with cellulase and cellulose are identified and discussed, which include hydrogen bonding, hydrophobic, electrostatic, and cation-π interactions, as well as physical barriers. Moreover, the effects of different conditions of EH that lead to cellulase deactivation by thermal and mechanical mechanisms are also explained. Finally, recent advances in the development, potential mechanisms, and economic feasibility of non-catalytic proteins on EH are evaluated and perspectives are presented.
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Affiliation(s)
- Meysam Madadi
- Key Laboratory of Industrial Biotechnology, Ministry of Education, School of Biotechnology, Jiangnan University, Wuxi, 214122, China
| | - Guojie Song
- Key Laboratory of Industrial Biotechnology, Ministry of Education, School of Biotechnology, Jiangnan University, Wuxi, 214122, China
| | - Fubao Sun
- Key Laboratory of Industrial Biotechnology, Ministry of Education, School of Biotechnology, Jiangnan University, Wuxi, 214122, China.
| | - Chihe Sun
- Key Laboratory of Industrial Biotechnology, Ministry of Education, School of Biotechnology, Jiangnan University, Wuxi, 214122, China
| | - Changlei Xia
- Jiangsu Co-Innovation Center of Efficient Processing and Utilization of Forest Resources, International Innovation Center for Forest Chemicals and Materials, College of Materials Science and Engineering, Nanjing Forestry University, Nanjing, Jiangsu, 210037, China
| | - Ezhen Zhang
- Institute of Agro-Products Processing Science and Technology, Guangxi Academy of Agricultural Sciences, Nanning, 530007, China
| | - Keikhosro Karimi
- Department of Chemical Engineering, Isfahan University of Technology, Isfahan, 84156-83111, Iran
| | - Maobing Tu
- Department of Chemical and Environmental Engineering, University of Cincinnati, Cincinnati, OH, 45221, United States
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Zhang F, Bunterngsook B, Li JX, Zhao XQ, Champreda V, Liu CG, Bai FW. Regulation and production of lignocellulolytic enzymes from Trichoderma reesei for biofuels production. ADVANCES IN BIOENERGY 2019. [DOI: 10.1016/bs.aibe.2019.03.001] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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Smit AT, Huijgen WJJ. The promotional effect of water-soluble extractives on the enzymatic cellulose hydrolysis of pretreated wheat straw. BIORESOURCE TECHNOLOGY 2017; 243:994-999. [PMID: 28753744 DOI: 10.1016/j.biortech.2017.07.072] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/11/2017] [Revised: 07/12/2017] [Accepted: 07/13/2017] [Indexed: 06/07/2023]
Abstract
Enzymatic cellulose hydrolysis of pretreated wheat straw pulp to glucose is enhanced when the hydrolysis is performed in the presence of an aqueous extract of the wheat straw. A relative digestibility increase of about 10% has been observed for organosolv, alkaline and dilute acid pretreated wheat straw pulp (enzyme dose 2.5FPU/g pulp). At lower enzyme doses, the extract effect increases leading to an enzyme dose reduction of 40% to obtain a glucose yield of 75% within 48h using organosolv wheat straw pulp. Possibly, cellulase deactivation by irreversible binding to pulp lignin is reduced by competition with proteins in the extract. However, since the extract effect has also been demonstrated for lignin-lean substrates, other effects like improved accessibility of the pulp cellulose (amorphogenesis) cannot be excluded. Overall, this contribution demonstrates the positive effect of biomass extractives on enzymatic cellulose digestibility, thereby reducing costs for 2G biofuels and bio-based chemicals.
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Affiliation(s)
- A T Smit
- Energy Research Centre of the Netherlands (ECN), Biomass & Energy Efficiency, P.O. Box 1, 1755 ZG Petten, The Netherlands.
| | - W J J Huijgen
- Energy Research Centre of the Netherlands (ECN), Biomass & Energy Efficiency, P.O. Box 1, 1755 ZG Petten, The Netherlands
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Artzi L, Morag E, Shamshoum M, Bayer EA. Cellulosomal expansin: functionality and incorporation into the complex. BIOTECHNOLOGY FOR BIOFUELS 2016; 9:61. [PMID: 26973715 PMCID: PMC4788839 DOI: 10.1186/s13068-016-0474-5] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/19/2016] [Accepted: 03/02/2016] [Indexed: 05/24/2023]
Abstract
BACKGROUND Expansins are relatively small proteins that lack enzymatic activity and are found in plants and microorganisms. The function of these proteins is to disrupt the plant cell walls by interfering with the non-covalent interchain bonding of the polysaccharides. Expansins were found to be important for plant growth, but they are also expressed by various bacteria known to have interactions with plants. Clostridium clariflavum is a plant cell wall-degrading bacterium with a highly elaborate cellulosomal system. Among its numerous dockerin-containing genes, two expansin-like proteins, Clocl_1862 and Clocl_1298 (termed herein CclEXL1 and CclEXL2) were identified, and CclEXL1 was found to be expressed as part of the cellulosome system. This is the first time that an expansin-like protein is identified in a cellulosome complex, which implicates its possible role in biomass deconstruction. RESULTS In the present article, we analyzed the functionality of CclEXL1. Its dockerin was characterized and shown to bind selectively to type-I cohesins of C. clariflavum, with preferential binding to the cohesin of ScaG, and additionally to a type-I cohesin of C. cellulolyticum. We demonstrated experimentally that the expansin-like protein binds preferentially to microcrystalline cellulose, but it also binds to acid-swollen cellulose, xylan, and wheat straw. CclEXL1 exhibited a pronounced loosening effect on filter paper, which resulted in substantial decrease in tensile stress. The C. clariflavum expansin-like protein thus enhances significantly enzymatic hydrolysis of cellulose, both by C. clariflavum cellulosomes and two major cellulosomal cellulases from this bacterium: GH48 (exoglucanase) and GH9 (endoglucanase). Finally, we demonstrated CclEXL1-mediated enhancement of microcrystalline cellulose degradation by different cellulosome fractions and the two enzymes. CONCLUSIONS The results of this study confirm that the C. clariflavum expansin-like protein is part of the elaborate cellulosome system of this bacterium with capabilities of cellulose creeping. The data suggest that pretreatment of cellulosic materials with CclEXL1 can bring about substantial improvement of hydrolysis by cellulases.
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Affiliation(s)
- Lior Artzi
- Department of Molecular Biosciences, The Weizmann Institute of Science, Rehovot, Israel
| | - Ely Morag
- Department of Molecular Biosciences, The Weizmann Institute of Science, Rehovot, Israel
| | - Melina Shamshoum
- Department of Molecular Biosciences, The Weizmann Institute of Science, Rehovot, Israel
| | - Edward A. Bayer
- Department of Molecular Biosciences, The Weizmann Institute of Science, Rehovot, Israel
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7
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Research advances in expansins and expansion-like proteins involved in lignocellulose degradation. Biotechnol Lett 2015; 37:1541-51. [DOI: 10.1007/s10529-015-1842-0] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2015] [Accepted: 04/29/2015] [Indexed: 12/12/2022]
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Bunterngsook B, Eurwilaichitr L, Thamchaipenet A, Champreda V. Binding characteristics and synergistic effects of bacterial expansins on cellulosic and hemicellulosic substrates. BIORESOURCE TECHNOLOGY 2015; 176:129-35. [PMID: 25460993 DOI: 10.1016/j.biortech.2014.11.042] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/16/2014] [Revised: 11/05/2014] [Accepted: 11/06/2014] [Indexed: 05/26/2023]
Abstract
Expansins are non-catalytic proteins which loosen plant cell wall structure. In this study, binding kinetics and synergistic action of five bacterial expansins on cellulosic and hemicellulosic polysaccharides were studied. The expansins differed in binding capacity (Bmax) and affinity (Kd) for different substrates. A common pattern of binding efficiency (Bmax/Kd) was found among the expansins tested, in which efficiency was greatest for the phosphoric acid-swollen cellulose (PASC), then the hemicellulose arabinoxylan followed by the microcrystalline cellulose (Avicel PH101). The expansins enhanced the action of Trichoderma reesei cellulase/hemicellulase mixture for degrading all three substrates to varying degrees. Among the substrates and expansins tested, BpEX from Bacillus pumilus and CmEX from Clavibacter michiganensis showed the greatest enhancement effect on arabinoxylan with 11.4 and 12.2-fold greater reducing sugar yield than the reaction with enzyme alone. The work gives insights into the wider application of expansins on enhancing polysaccharide hydrolysis, particularly on hemicellulosic substrates.
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Affiliation(s)
- Benjarat Bunterngsook
- Department of Genetics, Faculty of Sciences, Kasetsart University, Chatuchak, Bangkok 10900, Thailand
| | - Lily Eurwilaichitr
- Enzyme Technology Laboratory, Bioresources Technology Unit, National Center for Genetic Engineering and Biotechnology, Thailand Science Park, Khlong Luang, Pathum Thani 12120, Thailand.
| | - Arinthip Thamchaipenet
- Department of Genetics, Faculty of Sciences, Kasetsart University, Chatuchak, Bangkok 10900, Thailand
| | - Verawat Champreda
- Enzyme Technology Laboratory, Bioresources Technology Unit, National Center for Genetic Engineering and Biotechnology, Thailand Science Park, Khlong Luang, Pathum Thani 12120, Thailand
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Kazemi A, Rasoul-Amini S, Shahbazi M, Safari A, Ghasemi Y. Isolation, identification, and media optimization of high-level cellulase production by Bacillus sp. BCCS A3, in a fermentation system using response surface methodology. Prep Biochem Biotechnol 2014; 44:107-18. [PMID: 24152098 DOI: 10.1080/10826068.2013.792276] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Cellulases are important glycosyl hydrolase enzymes, which break down cellulose to β-glucose. They have been used widely in biotechnological processing such as bioethanol production. In this work we studied maximizing cellulase production by Bacillus sp. BCCS A3 using response surface methodology (RSM). A good result was attained with these conditions (% w/v): tryptone 0.1, Na₂PO₄ 0.25, (NH₄)₂SO₄ 0.2, MgSO₄ · 7H₂O 0.005, CaCl₂ 0.005, KH₂PO₄ 0.1, NaCl 0.1, sodium carboxymethylcellulose (CMC) 0.75, and pH 9. The cellulase activity in optimized medium was 49.80 U/ml. Moreover, high level of enzyme production was obtained by using fermentor system (50.30 U/ml). Thus, according to the obtained results, this statistical method provided quick identification and integration of key medium details for Bacillus sp. BCCS A3, leading to more cellulase production.
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Affiliation(s)
- Aboozar Kazemi
- a Pharmaceutical Sciences Research Center, Shiraz University of Medical Sciences , Shiraz , Iran
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10
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Bunterngsook B, Mhuantong W, Champreda V, Thamchaipenet A, Eurwilaichitr L. Identification of novel bacterial expansins and their synergistic actions on cellulose degradation. BIORESOURCE TECHNOLOGY 2014; 159:64-71. [PMID: 24632627 DOI: 10.1016/j.biortech.2014.02.004] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/18/2013] [Revised: 01/29/2014] [Accepted: 02/01/2014] [Indexed: 06/03/2023]
Abstract
Novel expansins, non-catalytic proteins which induce weakening of the rigid cellulose structure, have been identified in this study. A pipeline of bioinformatics was implemented for sequence and structure-based prediction of putative bacterial expansin-like group × family from NR databases. All putative expansins had no detectable activity against cellulosic and hemicellulosic substrates but showed varying degrees of synergy (2.0-7.6 folds) with the commercial Trichoderma reesei cellulase (Celluclast™ 1.5L) on degradation of filter paper in order of BpEX ≈ CmEX > MaEX > PcEX > SaEX. A mixture design with full cubic model predicted optimal formulation comprising Celluclast™: CmEX from Clavibacter michiganensis = 72.4%: 27.6%, with no synergy of β-glucosidase on degradation of alkaline pretreated rice straw. Under these conditions, the reducing sugar yield was 163.6% compared with the reaction containing cellulase alone. This work demonstrated the potential benefit of novel bacterial expansins on enhancing cellulose degradation efficiency in lignocellulosic biomass degradation.
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Affiliation(s)
- Benjarat Bunterngsook
- Department of Genetics, Faculty of Sciences, Kasetsart University, Chatuchak, Bangkok 10900, Thailand
| | - Wuttichai Mhuantong
- Enzyme Technology Laboratory, Bioresources Technology Unit, National Center for Genetic Engineering and Biotechnology, Thailand Science Park, Klong Luang, Pathumthani 12120, Thailand
| | - Verawat Champreda
- Enzyme Technology Laboratory, Bioresources Technology Unit, National Center for Genetic Engineering and Biotechnology, Thailand Science Park, Klong Luang, Pathumthani 12120, Thailand
| | - Arinthip Thamchaipenet
- Department of Genetics, Faculty of Sciences, Kasetsart University, Chatuchak, Bangkok 10900, Thailand
| | - Lily Eurwilaichitr
- Enzyme Technology Laboratory, Bioresources Technology Unit, National Center for Genetic Engineering and Biotechnology, Thailand Science Park, Klong Luang, Pathumthani 12120, Thailand.
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Qin YM, Tao H, Liu YY, Wang YD, Zhang JR, Tang AX. A novel non-hydrolytic protein from Pseudomonas oryzihabitans enhances the enzymatic hydrolysis of cellulose. J Biotechnol 2013; 168:24-31. [PMID: 23916949 DOI: 10.1016/j.jbiotec.2013.07.028] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2013] [Revised: 06/19/2013] [Accepted: 07/23/2013] [Indexed: 10/26/2022]
Abstract
Several kinds of protein such as the expansin, expansin-like proteins and LPMOs (lytic polysaccharide monooxygenases) are known to exert enhancement effects on cellulase activity. In this study, a novel cellulase synergistic protein named POEP1 was purified from the culture filtrate of Pseudomonas oryzihabitans CGMCC 6169, and was homogeneous on SDS-PAGE with a molecular weight of 60kDa. Mass spectrometry analysis indicated that it was an unknown protein without sequence similarity to the expansin and expansin-like proteins. Evaluation of the enzymatic hydrolysis of filter paper revealed that POEP1 had no cellulase activity but displayed high synergistic activity of 364% at a cellulase concentration of 0.1FPU/g of filter paper. When a mixture containing 0.6FPU cellulase and 700μg POEP1 per g of cellulose was evaluated, the maximal sugar yield was achieved, which was 2.2-fold greater than that with the cellulase alone. POEP1 was found to have functional similarity to the expansin and expansin-like proteins, which could decrease both the hydrogen-bond intensity and crystallinity, and cause the filter paper disruption. This study provided evidence for the existence of novel bacterial proteins in nature serving the same function as expansin and expansin-like proteins.
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Affiliation(s)
- Yi-Min Qin
- School of Chemistry and Chemical Engineering, Guangxi University, Nanning 530004, Guangxi, PR China; Guangxi Key Laboratory of Biorefinery, Nanning 530003, Guangxi, PR China
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12
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Han Y, Chen H. Enhancement of nanofiber elasticity by using wheat glutenin as an addition. POLYMER SCIENCE SERIES A 2013. [DOI: 10.1134/s0965545x13050076] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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13
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Abstract
Study on extract protein from long-term room temperature storage of wheat straw,utilize L9(34) Orthogonal experiment on the basis of single factor test.Study the impact of extraction time,extraction temperature and solid-liquid ratio on protein extraction yield of wheat straw.Result show factors affect wheat straw protein extraction rate in the order of extraction time>extraction temperature>liquid ratio>blank test,the optimal conditions is 50°C, the solid-liquid ratio 1:20 extract for 12 hours.Measured extraction yield is 21.761%.
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Van Dyk JS, Pletschke BI. A review of lignocellulose bioconversion using enzymatic hydrolysis and synergistic cooperation between enzymes--factors affecting enzymes, conversion and synergy. Biotechnol Adv 2012; 30:1458-80. [PMID: 22445788 DOI: 10.1016/j.biotechadv.2012.03.002] [Citation(s) in RCA: 477] [Impact Index Per Article: 39.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2011] [Revised: 02/10/2012] [Accepted: 03/06/2012] [Indexed: 02/04/2023]
Abstract
Lignocellulose is a complex substrate which requires a variety of enzymes, acting in synergy, for its complete hydrolysis. These synergistic interactions between different enzymes have been investigated in order to design optimal combinations and ratios of enzymes for different lignocellulosic substrates that have been subjected to different pretreatments. This review examines the enzymes required to degrade various components of lignocellulose and the impact of pretreatments on the lignocellulose components and the enzymes required for degradation. Many factors affect the enzymes and the optimisation of the hydrolysis process, such as enzyme ratios, substrate loadings, enzyme loadings, inhibitors, adsorption and surfactants. Consideration is also given to the calculation of degrees of synergy and yield. A model is further proposed for the optimisation of enzyme combinations based on a selection of individual or commercial enzyme mixtures. The main area for further study is the effect of and interaction between different hemicellulases on complex substrates.
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Affiliation(s)
- J S Van Dyk
- Department of Biochemistry, Microbiology and Biotechnology, Rhodes University, PO Box 94, Grahamstown, 6140, South Africa
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15
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Cellulolytic Enzyme Production and Enzymatic Hydrolysis for Second-Generation Bioethanol Production. ADVANCES IN BIOCHEMICAL ENGINEERING/BIOTECHNOLOGY 2012; 128:1-24. [DOI: 10.1007/10_2011_131] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
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16
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Lin H, Wang B, Zhuang R, Zhou Q, Zhao Y. Artificial construction and characterization of a fungal consortium that produces cellulolytic enzyme system with strong wheat straw saccharification. BIORESOURCE TECHNOLOGY 2011; 102:10569-10576. [PMID: 21924894 DOI: 10.1016/j.biortech.2011.08.095] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/19/2011] [Revised: 07/10/2011] [Accepted: 08/22/2011] [Indexed: 05/31/2023]
Abstract
A consortium-APcT2 composed of 92% of Trichoderma sp. T-1, 6.7% of P. chrysosporium and 1.3% of A. oryzae A-4 that produces cellulolytic enzyme system with strong wheat straw saccharification was constructed using Taguchi design combined with variance analysis (ANOVA). Among 32 consortia constructed from 6 fungi using Taguchi design, consortium 20 with the strongest composition was selected. The inhibitive fungal constituent in consortium 20 was subsequently removed according to the ANOVA results. The finally optimized consortium-APcT2 yielded 805.12 mg gds(-1) sugars, 26.98% higher than the pure Trichoderma sp. T-1. Protein profile analysis of the cellulolytic enzyme systems, sugar composition analysis of the hydrolysates and compatibility evaluation of the fungal constituents showed that the enhanced straw saccharification of the consortium-APcT2 could be mainly attributed to the enhancement of the co-cultivation for enzyme production and the synergistic action of different types of enzymes in the hydrolysis process.
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Affiliation(s)
- Hui Lin
- Institute of Microbiology, College of Life Sciences, Zhejiang University, Hangzhou 310058, People's Republic of China
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Jäger G, Girfoglio M, Dollo F, Rinaldi R, Bongard H, Commandeur U, Fischer R, Spiess AC, Büchs J. How recombinant swollenin from Kluyveromyces lactis affects cellulosic substrates and accelerates their hydrolysis. BIOTECHNOLOGY FOR BIOFUELS 2011; 4:33. [PMID: 21943248 PMCID: PMC3203333 DOI: 10.1186/1754-6834-4-33] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/07/2011] [Accepted: 09/23/2011] [Indexed: 05/02/2023]
Abstract
BACKGROUND In order to generate biofuels, insoluble cellulosic substrates are pretreated and subsequently hydrolyzed with cellulases. One way to pretreat cellulose in a safe and environmentally friendly manner is to apply, under mild conditions, non-hydrolyzing proteins such as swollenin - naturally produced in low yields by the fungus Trichoderma reesei. To yield sufficient swollenin for industrial applications, the first aim of this study is to present a new way of producing recombinant swollenin. The main objective is to show how swollenin quantitatively affects relevant physical properties of cellulosic substrates and how it affects subsequent hydrolysis. RESULTS After expression in the yeast Kluyveromyces lactis, the resulting swollenin was purified. The adsorption parameters of the recombinant swollenin onto cellulose were quantified for the first time and were comparable to those of individual cellulases from T. reesei. Four different insoluble cellulosic substrates were then pretreated with swollenin. At first, it could be qualitatively shown by macroscopic evaluation and microscopy that swollenin caused deagglomeration of bigger cellulose agglomerates as well as dispersion of cellulose microfibrils (amorphogenesis). Afterwards, the effects of swollenin on cellulose particle size, maximum cellulase adsorption and cellulose crystallinity were quantified. The pretreatment with swollenin resulted in a significant decrease in particle size of the cellulosic substrates as well as in their crystallinity, thereby substantially increasing maximum cellulase adsorption onto these substrates. Subsequently, the pretreated cellulosic substrates were hydrolyzed with cellulases. Here, pretreatment of cellulosic substrates with swollenin, even in non-saturating concentrations, significantly accelerated the hydrolysis. By correlating particle size and crystallinity of the cellulosic substrates with initial hydrolysis rates, it could be shown that the swollenin-induced reduction in particle size and crystallinity resulted in high cellulose hydrolysis rates. CONCLUSIONS Recombinant swollenin can be easily produced with the robust yeast K. lactis. Moreover, swollenin induces deagglomeration of cellulose agglomerates as well as amorphogenesis (decrystallization). For the first time, this study quantifies and elucidates in detail how swollenin affects different cellulosic substrates and their hydrolysis.
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Affiliation(s)
- Gernot Jäger
- AVT-Aachener Verfahrenstechnik, Biochemical Engineering, RWTH Aachen University,
Worringerweg 1, D-52074 Aachen, Germany
| | - Michele Girfoglio
- Institute of Molecular Biotechnology, RWTH Aachen University, Worringerweg 1,
D-52074 Aachen, Germany
| | - Florian Dollo
- AVT-Aachener Verfahrenstechnik, Biochemical Engineering, RWTH Aachen University,
Worringerweg 1, D-52074 Aachen, Germany
| | - Roberto Rinaldi
- Max-Planck-Institut für Kohlenforschung, Kaiser-Wilhelm-Platz 1, D-45470
Mülheim an der Ruhr, Germany
| | - Hans Bongard
- Max-Planck-Institut für Kohlenforschung, Kaiser-Wilhelm-Platz 1, D-45470
Mülheim an der Ruhr, Germany
| | - Ulrich Commandeur
- Institute of Molecular Biotechnology, RWTH Aachen University, Worringerweg 1,
D-52074 Aachen, Germany
| | - Rainer Fischer
- Institute of Molecular Biotechnology, RWTH Aachen University, Worringerweg 1,
D-52074 Aachen, Germany
- Fraunhofer Institute for Molecular Biology and Applied Ecology (IME),
Forckenbeckstrasse 6, D-52074 Aachen, Germany
| | - Antje C Spiess
- AVT-Aachener Verfahrenstechnik, Enzyme Process Technology, RWTH Aachen University,
Worringerweg 1, D-52074 Aachen, Germany
| | - Jochen Büchs
- AVT-Aachener Verfahrenstechnik, Biochemical Engineering, RWTH Aachen University,
Worringerweg 1, D-52074 Aachen, Germany
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18
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Gao L, Wang F, Gao F, Wang L, Zhao J, Qu Y. Purification and characterization of a novel cellobiohydrolase (PdCel6A) from Penicillium decumbens JU-A10 for bioethanol production. BIORESOURCE TECHNOLOGY 2011; 102:8339-42. [PMID: 21723116 DOI: 10.1016/j.biortech.2011.06.033] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/05/2011] [Revised: 06/07/2011] [Accepted: 06/08/2011] [Indexed: 05/02/2023]
Abstract
An acidic Cel6A, cellobiohydrolase (CBH) II, was purified from Penicillium decumbens and designated as PdCel6A. The deduced internal amino acid sequence of the novel CBH has a high degree of sequence identity with the CBH II from Aspergillus fumigatus. Surprisingly, PdCel6A exhibits characteristics comparable to that of CBH I, as well as CBH II. Similar to CBH I, the novel CBH has a specific activity of 1.9 IU/mg against p-nitrophenyl-β-d-cellobioside. The enzyme retains about 80% of its maximum activity after 4h of incubation at pH 2.0. Using delignified corncob residue as the substrate, ethanol concentration increased by 20% during simultaneous saccharification and fermentation when supplemented with low doses of PdCel6A (0.2mg/g substrate). To our knowledge, this is the first report involving a CBH I-like CBH II. The present paper provides new insight into the role of CBH II in cellulose degradation.
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Affiliation(s)
- Le Gao
- State Key Laboratory of Microbial Technology, Shandong University, Jinan 250100, PR China
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19
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Han Y, Chen H. Improvement of corn stover bioconversion efficiency by using plant glycoside hydrolase. BIORESOURCE TECHNOLOGY 2011; 102:4787-92. [PMID: 21300542 DOI: 10.1016/j.biortech.2011.01.015] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/11/2010] [Revised: 01/04/2011] [Accepted: 01/06/2011] [Indexed: 05/23/2023]
Abstract
Plant cell wall is the most abundant substrate for bioethanol production, and plants also represent a key resource for glycoside hydrolase (GH). To exploit efficient way for bioethanol production with lower cellulase loading, the potential of plant GH for lignocellulose bioconversion was evaluated. The GH activity for cell wall proteins (CWPs) was detected from fresh corn stover (FCS), and the synergism of which with Trichoderma reesei cellulase was also observed. The properties for the GH of FCS make it a promising enzyme additive for lignocellulose biodegradation. To make use of the plant GH, novel technology for hydrolysis and ethanol fermentation was developed with corn stover as substrate. Taking steam-exploded corn stover as substrate for hydrolysis and ethanol fermentation, compared with T. reesei cellulase loaded alone, the final glucose and ethanol accumulation increased by 60% and 63% respectively with GH of FCS as an addition.
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Affiliation(s)
- Yejun Han
- National Key Laboratory of Biochemical Engineering, Institute of Process Engineering, Chinese Academy of Sciences, Beijing 100190, China
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20
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Hydrolytic Enzyme of Cellulose for Complex Formulation Applied Research. Appl Biochem Biotechnol 2010; 164:23-33. [DOI: 10.1007/s12010-010-9111-0] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2010] [Accepted: 10/11/2010] [Indexed: 11/26/2022]
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21
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Han Y, Chen H. Biochemical characterization of a maize stover beta-exoglucanase and its use in lignocellulose conversion. BIORESOURCE TECHNOLOGY 2010; 101:6111-6117. [PMID: 20304632 DOI: 10.1016/j.biortech.2010.02.108] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/11/2010] [Revised: 02/21/2010] [Accepted: 02/25/2010] [Indexed: 05/29/2023]
Abstract
Plant is one of the important resources for glycosyl hydrolase production. A beta-exoglucanase with molecular weight of 63.1 kDa was purified from fresh maize stover and subjected to enzymatic characterization. The optimal temperature and pH of the beta-exoglucanase was 40 degrees C and 6.0, respectively. The beta-exoglucanase was active against p-nitrophenyl-cellobiose (p-NPC), laminarin, cellotriose, cellotetraose, cellopentaose, Avicel, filter paper, and cotton cellulose. The analysis of hydrolytic mode suggested that the beta-exoglucanase removed cellobiose from the ends of beta-glucan. Kinetic parameters of the beta-exoglucanase for laminarin and p-NPC were determined. The effects of metal ions and chemical reagents on the beta-exoglucanase activity were also studied. The biochemical characterization of the beta-exoglucanase makes it an appealing cellulase additive in converting lignocelluloses to ethanol through simultaneous saccharification and fermentation. The synergism of the beta-exoglucanase or crude cell wall proteins of fresh maize stover with Trichoderma reesei cellulase was observed in ethanol production from lignocellulose.
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Affiliation(s)
- Yejun Han
- National Key Laboratory of Biochemical Engineering, Institute of Process Engineering, Chinese Academy of Sciences, Beijing 100190, China
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22
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Gilbert HJ. The biochemistry and structural biology of plant cell wall deconstruction. PLANT PHYSIOLOGY 2010; 153:444-55. [PMID: 20406913 PMCID: PMC2879781 DOI: 10.1104/pp.110.156646] [Citation(s) in RCA: 217] [Impact Index Per Article: 15.5] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/23/2010] [Accepted: 04/17/2010] [Indexed: 05/18/2023]
Affiliation(s)
- Harry J Gilbert
- Complex Carbohydrate Research Center, University of Georgia, Athens, Georgia 30602, USA.
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23
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Arantes V, Saddler JN. Access to cellulose limits the efficiency of enzymatic hydrolysis: the role of amorphogenesis. BIOTECHNOLOGY FOR BIOFUELS 2010; 3:4. [PMID: 20178562 PMCID: PMC2844368 DOI: 10.1186/1754-6834-3-4] [Citation(s) in RCA: 294] [Impact Index Per Article: 21.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/13/2009] [Accepted: 02/23/2010] [Indexed: 05/02/2023]
Abstract
The efficient enzymatic saccharification of cellulose at low cellulase (protein) loadings continues to be a challenge for commercialization of a process for bioconversion of lignocellulose to ethanol. Currently, effective pretreatment followed by high enzyme loading is needed to overcome several substrate and enzyme factors that limit rapid and complete hydrolysis of the cellulosic fraction of biomass substrates. One of the major barriers faced by cellulase enzymes is their limited access to much of the cellulose that is buried within the highly ordered and tightly packed fibrillar architecture of the cellulose microfibrils. Rather than a sequential 'shaving' or 'planing' of the cellulose fibrils from the outside, it has been suggested that these inaccessible regions are disrupted or loosened by non-hydrolytic proteins, thereby increasing the cellulose surface area and making it more accessible to the cellulase enzyme complex. This initial stage in enzymatic saccharification of cellulose has been termed amorphogenesis. In this review, we describe the various amorphogenesis-inducing agents that have been suggested, and their possible role in enhancing the enzymatic hydrolysis of cellulose.
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Affiliation(s)
- Valdeir Arantes
- Forestry Products Biotechnology/Bioenergy Group, Department of Wood Science, Faculty of Forestry, University of British Columbia, 2424 Main Mall, Vancouver BC, V6T 1Z4, Canada
| | - Jack N Saddler
- Forestry Products Biotechnology/Bioenergy Group, Department of Wood Science, Faculty of Forestry, University of British Columbia, 2424 Main Mall, Vancouver BC, V6T 1Z4, Canada
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24
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Synergism between hydrophobic proteins of corn stover and cellulase in lignocellulose hydrolysis. Biochem Eng J 2010. [DOI: 10.1016/j.bej.2009.10.013] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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25
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Abstract
Despite the presence of many carbohydrolytic activities in insects, their cellulolytic mechanisms are poorly understood. Whereas cellulase genes are absent from the genomes of Drosophila melanogaster or Bombyx mori, other insects such as termites produce their own cellulases. Recent studies using molecular biological techniques have brought new insights into the mechanisms by which the insects and their microbial symbionts digest cellulose in the small intestine. DNA sequences of cellulase and associated genes, as well as physiological and morphological information about the digestive systems of cellulase-producing insects, may allow the efficient use of cellulosic biomass as a sustainable energy source.
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Affiliation(s)
- Hirofumi Watanabe
- National Institute of Agrobiological Sciences, 1-2 Owashi, Tsukuba, Ibaraki, Japan.
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26
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Vaaje-Kolstad G, Bunaes AC, Mathiesen G, Eijsink VGH. The chitinolytic system of Lactococcus lactis ssp. lactis comprises a nonprocessive chitinase and a chitin-binding protein that promotes the degradation of alpha- and beta-chitin. FEBS J 2009; 276:2402-15. [PMID: 19348025 DOI: 10.1111/j.1742-4658.2009.06972.x] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
It has recently been shown that the Gram-negative bacterium Serratia marcescens produces an accessory nonhydrolytic chitin-binding protein that acts in synergy with chitinases. This provided the first example of the production of dedicated helper proteins for the turnover of recalcitrant polysaccharides. Chitin-binding proteins belong to family 33 of the carbohydrate-binding modules, and genes putatively encoding these proteins occur in many microorganisms. To obtain an impression of the functional conservation of these proteins, we studied the chitinolytic system of the Gram-positive Lactococcus lactis ssp. lactis IL1403. The genome of this lactic acid bacterium harbours a simple chitinolytic machinery, consisting of one family 18 chitinase (named LlChi18A), one family 33 chitin-binding protein (named LlCBP33A) and one family 20 N-acetylhexosaminidase. We cloned, overexpressed and characterized LlChi18A and LlCBP33A. Sequence alignments and structural modelling indicated that LlChi18A has a shallow substrate-binding groove characteristic of nonprocessive endochitinases. Enzymology showed that LlChi18A was able to hydrolyse both chitin oligomers and artificial substrates, with no sign of processivity. Although the chitin-binding protein from S. marcescens only bound to beta-chitin, LlCBP33A was found to bind to both alpha- and beta-chitin. LlCBP33A increased the hydrolytic efficiency of LlChi18A to both alpha- and beta-chitin. These results show the general importance of chitin-binding proteins in chitin turnover, and provide the first example of a family 33 chitin-binding protein that increases chitinase efficiency towards alpha-chitin.
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Affiliation(s)
- Gustav Vaaje-Kolstad
- Department of Chemistry, Biotechnology and Food Science, Norwegian University of Life Sciences, As, Norway.
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27
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Kim ES, Lee HJ, Bang WG, Choi IG, Kim KH. Functional characterization of a bacterial expansin from Bacillus subtilis for enhanced enzymatic hydrolysis of cellulose. Biotechnol Bioeng 2009; 102:1342-53. [PMID: 19058186 DOI: 10.1002/bit.22193] [Citation(s) in RCA: 100] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
Expansin is a plant protein family that induces plant cell wall-loosening and cellulose disruption without exerting cellulose-hydrolytic activity. Expansin-like proteins have also been found in other eukaryotes such as nematodes and fungi. While searching for an expansin produced by bacteria, we found that the BsEXLX1 protein from Bacillus subtilis had a structure that was similar to that of a beta-expansin produced by maize. Therefore, we cloned the BsEXLX1 gene and expressed it in Escherichia coli to evaluate its function. When incubated with filter paper as a cellulose substrate, the recombinant protein exhibited both cellulose-binding and cellulose-weakening activities, which are known functions of plant expansins. In addition, evaluation of the enzymatic hydrolysis of filter paper revealed that the recombinant protein also displayed a significant synergism when mixed with cellulase. By comparing the activity of a mixture of cellulase and the bacterial expansin to the additive activity of the individual proteins, the synergistic activity was found to be as high as 240% when filter paper was incubated with cellulase and BsEXLX1, which was 5.7-fold greater than the activity of cellulase alone. However, this synergistic effect was observed when only a low dosage of cellulase was used. This is the first study to characterize the function of an expansin produced by a non-eukaryotic source.
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Affiliation(s)
- Eun Sil Kim
- School of Life Sciences & Biotechnology, Korea University, Seoul 136-713, Republic of Korea
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28
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Kim ES, Lee HJ, Bang WG, Choi IG, Kim KH. A novel cellulase activity enhancing protein from bacillus subtilis, a functional homolog of a plant expansin. J Biotechnol 2008. [DOI: 10.1016/j.jbiotec.2008.07.986] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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29
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Plant genetic engineering for biofuel production: towards affordable cellulosic ethanol. Nat Rev Genet 2008; 9:433-43. [DOI: 10.1038/nrg2336] [Citation(s) in RCA: 396] [Impact Index Per Article: 24.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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30
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Eijsink VGH, Vaaje-Kolstad G, Vårum KM, Horn SJ. Towards new enzymes for biofuels: lessons from chitinase research. Trends Biotechnol 2008; 26:228-35. [PMID: 18367275 DOI: 10.1016/j.tibtech.2008.02.004] [Citation(s) in RCA: 105] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2007] [Revised: 02/08/2008] [Accepted: 02/15/2008] [Indexed: 10/22/2022]
Abstract
Enzymatic conversion of structural polysaccharides in plant biomass is a key issue in the development of second generation ('lignocellulosic') bioethanol. The efficiency of this process depends in part on the ability of enzymes to disrupt crystalline polysaccharides, thus gaining access to single polymer chains. Recently, new insights into how enzymes accomplish this have been obtained from studies on enzymatic conversion of chitin. First, chitinolytic microorganisms were shown to produce non-hydrolytic accessory proteins that increase enzyme efficiency. Second, it was shown that a processive mechanism, which is generally considered favorable because it improves substrate accessibility, might in fact slow down enzymes. These findings suggest new focal points for the development of enzyme technology for depolymerizing recalcitrant polysaccharide biomass. Improving substrate accessibility should be a key issue because this might reduce the need for using processive enzymes, which are intrinsically slow and abundantly present in current commercial enzyme preparations for biomass conversion. Furthermore, carefully selected substrate-disrupting accessory proteins or domains might provide novel tools to improve substrate accessibility and thus contribute to more efficient enzymatic processes.
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Affiliation(s)
- Vincent G H Eijsink
- Department of Chemistry, Biotechnology and Food Science, Norwegian University of Life Sciences, As, Norway.
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