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Aqeel A, Ahmed Z, Akram F, Abbas Q, Ikram-Ul-Haq. Cloning, expression and purification of cellobiohydrolase gene from Caldicellulosiruptor bescii for efficient saccharification of plant biomass. Int J Biol Macromol 2024; 271:132525. [PMID: 38797293 DOI: 10.1016/j.ijbiomac.2024.132525] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2024] [Revised: 05/04/2024] [Accepted: 05/18/2024] [Indexed: 05/29/2024]
Abstract
Anthropogenic activities have led to a drastic shift from natural fuels to alternative renewable energy reserves that demand heat-stable cellulases. Cellobiohydrolase is an indispensable member of cellulases that play a critical role in the degradation of cellulosic biomass. This article details the process of cloning the cellobiohydrolase gene from the thermophilic bacterium Caldicellulosiruptor bescii and expressing it in Escherichia coli (BL21) CondonPlus DE3-(RIPL) using the pET-21a(+) expression vector. Multi-alignments and structural modeling studies reveal that recombinant CbCBH contained a conserved cellulose binding domain III. The enzyme's catalytic site included Asp-372 and Glu-620, which are either involved in substrate or metal binding. The purified CbCBH, with a molecular weight of 91.8 kDa, displayed peak activity against pNPC (167.93 U/mg) at 65°C and pH 6.0. Moreover, it demonstrated remarkable stability across a broad temperature range (60-80°C) for 8 h. Additionally, the Plackett-Burman experimental model was employed to assess the saccharification of pretreated sugarcane bagasse with CbCBH, aiming to evaluate the cultivation conditions. The optimized parameters, including a pH of 6.0, a temperature of 55°C, a 24-hour incubation period, a substrate concentration of 1.5% (w/v), and enzyme activity of 120 U, resulted in an observed saccharification efficiency of 28.45%. This discovery indicates that the recombinant CbCBH holds promising potential for biofuel sector.
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Affiliation(s)
- Amna Aqeel
- Dr. Ikram-ul-Haq Institute of Industrial Biotechnology, Government College University Lahore, 54000, Pakistan.
| | - Zeeshan Ahmed
- Dr. Ikram-ul-Haq Institute of Industrial Biotechnology, Government College University Lahore, 54000, Pakistan
| | - Fatima Akram
- Dr. Ikram-ul-Haq Institute of Industrial Biotechnology, Government College University Lahore, 54000, Pakistan
| | - Qamar Abbas
- School of Biological Sciences, University of Punjab, Lahore 54000, Pakistan
| | - Ikram-Ul-Haq
- Dr. Ikram-ul-Haq Institute of Industrial Biotechnology, Government College University Lahore, 54000, Pakistan
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2
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Gennari A, Simon R, de Andrade BC, Saraiva Macedo Timmers LF, Milani Martins VL, Renard G, Chies JM, Volpato G, Volken de Souza CF. Production of beta-galactosidase fused to a cellulose-binding domain for application in sustainable industrial processes. BIORESOURCE TECHNOLOGY 2021; 326:124747. [PMID: 33517047 DOI: 10.1016/j.biortech.2021.124747] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/08/2020] [Revised: 01/14/2021] [Accepted: 01/15/2021] [Indexed: 06/12/2023]
Abstract
This study aimed to produce and characterize a recombinant Kluyveromyces sp. β-galactosidase fused to a cellulose-binding domain (CBD) for industrial application. In expression assays, the highest enzymatic activities occurred after 48 h induction on Escherichia coli C41(DE3) strain at 20 °C in Terrific Broth (TB) culture medium, using isopropyl β-d-1-thiogalactopyranoside (IPTG) 0.5 mM (108.77 U/mL) or lactose 5 g/L (93.10 U/mL) as inducers. Cultures at bioreactor scale indicated that higher product yield values in relation to biomass (2000 U/g) and productivity (0.72 U/mL.h) were obtained in culture media containing higher protein concentration. The recombinant enzyme showed high binding affinity to nanocellulose, reaching both immobilization yield and efficiency values of approximately 70% at pH 7.0 after 10 min reaction. The results of the present study pointed out a strategy for recombinant β-galactosidase-CBD production and immobilization, aiming toward the application in sustainable industrial processes using low-cost inputs.
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Affiliation(s)
- Adriano Gennari
- Laboratório de Biotecnologia de Alimentos, Universidade do Vale do Taquari - Univates, Lajeado, RS, Brazil; Programa de Pós-Graduação em Biotecnologia, Universidade do Vale do Taquari - Univates, Lajeado, RS, Brazil
| | - Renate Simon
- Laboratório de Biotecnologia de Alimentos, Universidade do Vale do Taquari - Univates, Lajeado, RS, Brazil
| | - Bruna Coelho de Andrade
- Laboratório de Biotecnologia de Alimentos, Universidade do Vale do Taquari - Univates, Lajeado, RS, Brazil; Programa de Pós-Graduação em Biotecnologia, Universidade do Vale do Taquari - Univates, Lajeado, RS, Brazil
| | | | - Vera Lúcia Milani Martins
- Instituto Federal de Educação, Ciência e Tecnologia do Rio Grande do Sul - IFRS, Campus Porto Alegre, Porto Alegre, RS, Brazil
| | - Gaby Renard
- Centro de Pesquisa em Biologia Molecular e Funcional, Pontifícia Universidade Católica do Rio Grande do Sul, Porto Alegre, RS, Brazil
| | | | - Giandra Volpato
- Instituto Federal de Educação, Ciência e Tecnologia do Rio Grande do Sul - IFRS, Campus Porto Alegre, Porto Alegre, RS, Brazil
| | - Claucia Fernanda Volken de Souza
- Laboratório de Biotecnologia de Alimentos, Universidade do Vale do Taquari - Univates, Lajeado, RS, Brazil; Programa de Pós-Graduação em Biotecnologia, Universidade do Vale do Taquari - Univates, Lajeado, RS, Brazil.
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3
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Kolinko S, Wu YW, Tachea F, Denzel E, Hiras J, Gabriel R, Bäcker N, Chan LJG, Eichorst SA, Frey D, Chen Q, Azadi P, Adams PD, Pray TR, Tanjore D, Petzold CJ, Gladden JM, Simmons BA, Singer SW. A bacterial pioneer produces cellulase complexes that persist through community succession. Nat Microbiol 2017; 3:99-107. [PMID: 29109478 PMCID: PMC6794216 DOI: 10.1038/s41564-017-0052-z] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2017] [Accepted: 10/04/2017] [Indexed: 11/16/2022]
Abstract
Cultivation of microbial consortia provides low-complexity communities that can serve as tractable models to understand community dynamics. Time-resolved metagenomics demonstrated that an aerobic cellulolytic consortium cultivated from compost exhibited community dynamics consistent with the definition of an endogenous heterotrophic succession. The genome of the proposed pioneer population, ‘Candidatus Reconcilibacillus cellulovorans’, possessed a gene cluster containing multidomain glycoside hydrolases (GHs). Purification of the soluble cellulase activity from a 300litre cultivation of this consortium revealed that ~70% of the activity arose from the ‘Ca. Reconcilibacillus cellulovorans’ multidomain GHs assembled into cellulase complexes through glycosylation. These remarkably stable complexes have supramolecular structures for enzymatic cellulose hydrolysis that are distinct from cellulosomes. The persistence of these complexes during cultivation indicates that they may be active through multiple cultivations of this consortium and act as public goods that sustain the community. The provision of extracellular GHs as public goods may influence microbial community dynamics in native biomass-deconstructing communities relevant to agriculture, human health and biotechnology. Cultivation of a cellulolytic consortium reveals successional community dynamics and the presence of multidomain glycoside hydrolases assembled into stable complexes distinct from cellulosomes, which are produced by a potential pioneer population.
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Affiliation(s)
- Sebastian Kolinko
- Joint BioEnergy Institute, Emeryville, CA, USA.,Biological Systems and Engineering Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA
| | - Yu-Wei Wu
- Joint BioEnergy Institute, Emeryville, CA, USA.,Biological Systems and Engineering Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA.,Graduate Institute of Biomedical Informatics, College of Medical Science and Technology, Taipei Medical University, Taipei, Taiwan
| | - Firehiwot Tachea
- Biological Systems and Engineering Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA.,Advanced Biofuels Process Development Unit, Lawrence Berkeley National Laboratory, Emeryville, CA, USA
| | - Evelyn Denzel
- Joint BioEnergy Institute, Emeryville, CA, USA.,Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA.,Faculty of Biotechnology, University of Applied Sciences, Mannheim, Germany
| | - Jennifer Hiras
- Joint BioEnergy Institute, Emeryville, CA, USA.,Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA.,Corning Incorporated, Corning, NY, USA
| | - Raphael Gabriel
- Joint BioEnergy Institute, Emeryville, CA, USA.,Biological Systems and Engineering Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA.,Institut für Genetik, Technische Universität Braunschweig, Braunschweig, Germany
| | - Nora Bäcker
- Joint BioEnergy Institute, Emeryville, CA, USA.,Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA.,Faculty of Biotechnology, University of Applied Sciences, Mannheim, Germany
| | - Leanne Jade G Chan
- Joint BioEnergy Institute, Emeryville, CA, USA.,Biological Systems and Engineering Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA
| | - Stephanie A Eichorst
- Joint BioEnergy Institute, Emeryville, CA, USA.,Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA.,Division of Microbial Ecology, Department of Microbiology and Ecosystem Science, Research network "Chemistry meets Microbiology", University of Vienna, Vienna, Austria
| | - Dario Frey
- Joint BioEnergy Institute, Emeryville, CA, USA.,Biological Systems and Engineering Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA.,Faculty of Biotechnology, University of Applied Sciences, Mannheim, Germany
| | - Qiushi Chen
- Complex Carbohydrate Research Center, University of Georgia, Athens, GA, USA
| | - Parastoo Azadi
- Complex Carbohydrate Research Center, University of Georgia, Athens, GA, USA
| | - Paul D Adams
- Joint BioEnergy Institute, Emeryville, CA, USA.,Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA
| | - Todd R Pray
- Biological Systems and Engineering Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA.,Advanced Biofuels Process Development Unit, Lawrence Berkeley National Laboratory, Emeryville, CA, USA
| | - Deepti Tanjore
- Biological Systems and Engineering Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA.,Advanced Biofuels Process Development Unit, Lawrence Berkeley National Laboratory, Emeryville, CA, USA
| | - Christopher J Petzold
- Joint BioEnergy Institute, Emeryville, CA, USA.,Biological Systems and Engineering Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA
| | - John M Gladden
- Joint BioEnergy Institute, Emeryville, CA, USA.,Biological and Materials Science Center, Sandia National Laboratories, Livermore, CA, USA
| | - Blake A Simmons
- Joint BioEnergy Institute, Emeryville, CA, USA.,Biological Systems and Engineering Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA
| | - Steven W Singer
- Joint BioEnergy Institute, Emeryville, CA, USA. .,Biological Systems and Engineering Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA.
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Impact of Module-X2 and Carbohydrate Binding Module-3 on the catalytic activity of associated glycoside hydrolases towards plant biomass. Sci Rep 2017. [PMID: 28623337 PMCID: PMC5473887 DOI: 10.1038/s41598-017-03927-y] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/04/2022] Open
Abstract
Cellulolytic enzymes capable of hydrolyzing plant biomass are secreted by microbial cells specifically in response to the carbon substrate present in the environment. These enzymes consist of a catalytic domain, generally appended to one or more non-catalytic Carbohydrate Binding Module (CBM), which enhances their activity towards recalcitrant biomass. In the present study, the genome of a cellulolytic microbe Paenibacillus polymyxa A18 was annotated for the presence of CBMs and analyzed their expression in response to the plant biomass and model polysaccharides Avicel, CMC and xylan using quantitative PCR. A gene that encodes X2-CBM3 was found to be maximally induced in response to the biomass and crystalline substrate Avicel. Association of X2-CBM3 with xyloglucanase and endoglucanase led to up to 4.6-fold increase in activity towards insoluble substrates. In the substrate binding study, module X2 showed a higher affinity towards biomass and phosphoric acid swollen cellulose, whereas CBM3 showed a higher affinity towards Avicel. Further structural modeling of X2 also indicated its potential role in substrate binding. Our findings highlighted the role of module X2 along with CBM3 in assisting the enzyme catalysis of agricultural residue and paved the way to engineer glycoside hydrolases for superior activity.
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Kumar A, Zhang S, Wu G, Wu CC, Chen J, Baskaran R, Liu Z. Cellulose binding domain assisted immobilization of lipase (GSlip–CBD) onto cellulosic nanogel: characterization and application in organic medium. Colloids Surf B Biointerfaces 2015; 136:1042-50. [DOI: 10.1016/j.colsurfb.2015.11.006] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2015] [Revised: 10/31/2015] [Accepted: 11/02/2015] [Indexed: 01/18/2023]
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Deng K, Guenther JM, Gao J, Bowen BP, Tran H, Reyes-Ortiz V, Cheng X, Sathitsuksanoh N, Heins R, Takasuka TE, Bergeman LF, Geertz-Hansen H, Deutsch S, Loqué D, Sale KL, Simmons BA, Adams PD, Singh AK, Fox BG, Northen TR. Development of a High Throughput Platform for Screening Glycoside Hydrolases Based on Oxime-NIMS. Front Bioeng Biotechnol 2015; 3:153. [PMID: 26528471 PMCID: PMC4603251 DOI: 10.3389/fbioe.2015.00153] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2015] [Accepted: 09/21/2015] [Indexed: 12/26/2022] Open
Abstract
Cost-effective hydrolysis of biomass into sugars for biofuel production requires high-performance low-cost glycoside hydrolase (GH) cocktails that are active under demanding process conditions. Improving the performance of GH cocktails depends on knowledge of many critical parameters, including individual enzyme stabilities, optimal reaction conditions, kinetics, and specificity of reaction. With this information, rate- and/or yield-limiting reactions can be potentially improved through substitution, synergistic complementation, or protein engineering. Given the wide range of substrates and methods used for GH characterization, it is difficult to compare results across a myriad of approaches to identify high performance and synergistic combinations of enzymes. Here, we describe a platform for systematic screening of GH activities using automatic biomass handling, bioconjugate chemistry, robotic liquid handling, and nanostructure-initiator mass spectrometry (NIMS). Twelve well-characterized substrates spanning the types of glycosidic linkages found in plant cell walls are included in the experimental workflow. To test the application of this platform and substrate panel, we studied the reactivity of three engineered cellulases and their synergy of combination across a range of reaction conditions and enzyme concentrations. We anticipate that large-scale screening using the standardized platform and substrates will generate critical datasets to enable direct comparison of enzyme activities for cocktail design.
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Affiliation(s)
- Kai Deng
- US Department of Energy Joint BioEnergy Institute , Emeryville, CA , USA ; Sandia National Laboratories , Livermore, CA , USA
| | - Joel M Guenther
- US Department of Energy Joint BioEnergy Institute , Emeryville, CA , USA ; Sandia National Laboratories , Livermore, CA , USA
| | - Jian Gao
- Lawrence Berkeley National Laboratory , Berkeley, CA , USA
| | | | - Huu Tran
- US Department of Energy Joint BioEnergy Institute , Emeryville, CA , USA ; Sandia National Laboratories , Livermore, CA , USA
| | - Vimalier Reyes-Ortiz
- US Department of Energy Joint BioEnergy Institute , Emeryville, CA , USA ; Lawrence Berkeley National Laboratory , Berkeley, CA , USA
| | - Xiaoliang Cheng
- US Department of Energy Joint BioEnergy Institute , Emeryville, CA , USA ; Lawrence Berkeley National Laboratory , Berkeley, CA , USA
| | - Noppadon Sathitsuksanoh
- US Department of Energy Joint BioEnergy Institute , Emeryville, CA , USA ; Lawrence Berkeley National Laboratory , Berkeley, CA , USA
| | - Richard Heins
- US Department of Energy Joint BioEnergy Institute , Emeryville, CA , USA ; Sandia National Laboratories , Livermore, CA , USA
| | - Taichi E Takasuka
- US Department of Energy Great Lakes Bioenergy Research Center, University of Wisconsin , Madison, WI , USA
| | - Lai F Bergeman
- US Department of Energy Great Lakes Bioenergy Research Center, University of Wisconsin , Madison, WI , USA
| | | | - Samuel Deutsch
- Lawrence Berkeley National Laboratory , Berkeley, CA , USA ; Joint Genome Institute , Walnut Creek, CA , USA
| | - Dominique Loqué
- US Department of Energy Joint BioEnergy Institute , Emeryville, CA , USA ; Lawrence Berkeley National Laboratory , Berkeley, CA , USA
| | - Kenneth L Sale
- US Department of Energy Joint BioEnergy Institute , Emeryville, CA , USA ; Sandia National Laboratories , Livermore, CA , USA
| | - Blake A Simmons
- US Department of Energy Joint BioEnergy Institute , Emeryville, CA , USA ; Sandia National Laboratories , Livermore, CA , USA
| | - Paul D Adams
- US Department of Energy Joint BioEnergy Institute , Emeryville, CA , USA ; Lawrence Berkeley National Laboratory , Berkeley, CA , USA ; Department of Bioengineering, University of California Berkeley , Berkeley, CA , USA
| | - Anup K Singh
- US Department of Energy Joint BioEnergy Institute , Emeryville, CA , USA ; Sandia National Laboratories , Livermore, CA , USA
| | - Brian G Fox
- US Department of Energy Great Lakes Bioenergy Research Center, University of Wisconsin , Madison, WI , USA ; Department of Biochemistry, University of Wisconsin , Madison, WI , USA
| | - Trent R Northen
- US Department of Energy Joint BioEnergy Institute , Emeryville, CA , USA ; Lawrence Berkeley National Laboratory , Berkeley, CA , USA
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7
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Petkun S, Rozman Grinberg I, Lamed R, Jindou S, Burstein T, Yaniv O, Shoham Y, Shimon LJ, Bayer EA, Frolow F. Reassembly and co-crystallization of a family 9 processive endoglucanase from its component parts: structural and functional significance of the intermodular linker. PeerJ 2015; 3:e1126. [PMID: 26401442 PMCID: PMC4579020 DOI: 10.7717/peerj.1126] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2015] [Accepted: 07/04/2015] [Indexed: 11/22/2022] Open
Abstract
Non-cellulosomal processive endoglucanase 9I (Cel9I) from Clostridium thermocellum is a modular protein, consisting of a family-9 glycoside hydrolase (GH9) catalytic module and two family-3 carbohydrate-binding modules (CBM3c and CBM3b), separated by linker regions. GH9 does not show cellulase activity when expressed without CBM3c and CBM3b and the presence of the CBM3c was previously shown to be essential for endoglucanase activity. Physical reassociation of independently expressed GH9 and CBM3c modules (containing linker sequences) restored 60-70% of the intact Cel9I endocellulase activity. However, the mechanism responsible for recovery of activity remained unclear. In this work we independently expressed recombinant GH9 and CBM3c with and without their interconnecting linker in Escherichia coli. We crystallized and determined the molecular structure of the GH9/linker-CBM3c heterodimer at a resolution of 1.68 Å to understand the functional and structural importance of the mutual spatial orientation of the modules and the role of the interconnecting linker during their re-association. Enzyme activity assays and isothermal titration calorimetry were performed to study and compare the effect of the linker on the re-association. The results indicated that reassembly of the modules could also occur without the linker, albeit with only very low recovery of endoglucanase activity. We propose that the linker regions in the GH9/CBM3c endoglucanases are important for spatial organization and fixation of the modules into functional enzymes.
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Affiliation(s)
- Svetlana Petkun
- Department of Molecular Microbiology and Biotechnology, The Daniella Rich Institute for Structural Biology, Tel Aviv University, Ramat Aviv, Israel
| | - Inna Rozman Grinberg
- Department of Molecular Microbiology and Biotechnology, The Daniella Rich Institute for Structural Biology, Tel Aviv University, Ramat Aviv, Israel
| | - Raphael Lamed
- Department of Molecular Microbiology and Biotechnology, The Daniella Rich Institute for Structural Biology, Tel Aviv University, Ramat Aviv, Israel
| | - Sadanari Jindou
- Department of Life Sciences, Meijo University, Nagoya, Japan
| | - Tal Burstein
- Department of Molecular Microbiology and Biotechnology, The Daniella Rich Institute for Structural Biology, Tel Aviv University, Ramat Aviv, Israel
| | - Oren Yaniv
- Department of Molecular Microbiology and Biotechnology, The Daniella Rich Institute for Structural Biology, Tel Aviv University, Ramat Aviv, Israel
| | - Yuval Shoham
- Department of Biotechnology and Food Engineering, Technion-Israel Institute of Technology, Haifa, Israel
| | - Linda J.W. Shimon
- Department of Chemical Research Support, The Weizmann Institute of Science, Rehovot, Israel
| | - Edward A. Bayer
- Department of Biological Chemistry, The Weizmann Institute of Science, Rehovot, Israel
| | - Felix Frolow
- Department of Molecular Microbiology and Biotechnology, The Daniella Rich Institute for Structural Biology, Tel Aviv University, Ramat Aviv, Israel
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Blumer-Schuette SE, Brown SD, Sander KB, Bayer EA, Kataeva I, Zurawski JV, Conway JM, Adams MWW, Kelly RM. Thermophilic lignocellulose deconstruction. FEMS Microbiol Rev 2014; 38:393-448. [DOI: 10.1111/1574-6976.12044] [Citation(s) in RCA: 128] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2012] [Revised: 08/20/2013] [Accepted: 08/28/2013] [Indexed: 11/28/2022] Open
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Mazzoli R. Development of microorganisms for cellulose-biofuel consolidated bioprocessings: metabolic engineers' tricks. Comput Struct Biotechnol J 2012; 3:e201210007. [PMID: 24688667 PMCID: PMC3962139 DOI: 10.5936/csbj.201210007] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2012] [Revised: 10/22/2012] [Accepted: 10/24/2012] [Indexed: 01/04/2023] Open
Abstract
Cellulose waste biomass is the most abundant and attractive substrate for "biorefinery strategies" that are aimed to produce high-value products (e.g. solvents, fuels, building blocks) by economically and environmentally sustainable fermentation processes. However, cellulose is highly recalcitrant to biodegradation and its conversion by biotechnological strategies currently requires economically inefficient multistep industrial processes. The need for dedicated cellulase production continues to be a major constraint to cost-effective processing of cellulosic biomass. Research efforts have been aimed at developing recombinant microorganisms with suitable characteristics for single step biomass fermentation (consolidated bioprocessing, CBP). Two paradigms have been applied for such, so far unsuccessful, attempts: a) "native cellulolytic strategies", aimed at conferring high-value product properties to natural cellulolytic microorganisms; b) "recombinant cellulolytic strategies", aimed to confer cellulolytic ability to microorganisms exhibiting high product yields and titers. By starting from the description of natural enzyme systems for plant biomass degradation and natural metabolic pathways for some of the most valuable product (i.e. butanol, ethanol, and hydrogen) biosynthesis, this review describes state-of-the-art bottlenecks and solutions for the development of recombinant microbial strains for cellulosic biofuel CBP by metabolic engineering. Complexed cellulases (i.e. cellulosomes) benefit from stronger proximity effects and show enhanced synergy on insoluble substrates (i.e. crystalline cellulose) with respect to free enzymes. For this reason, special attention was held on strategies involving cellulosome/designer cellulosome-bearing recombinant microorganisms.
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Affiliation(s)
- Roberto Mazzoli
- Department of Life Sciences and Systems Biology, University of Torino, Via Accademia Albertina 13, 10123 Torino, Italy
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