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van der Zwan T, Sigg A, Hu J, Chandra RP, Saddler JN. Enzyme-Mediated Lignocellulose Liquefaction Is Highly Substrate-Specific and Influenced by the Substrate Concentration or Rheological Regime. Front Bioeng Biotechnol 2020; 8:917. [PMID: 32850753 PMCID: PMC7423843 DOI: 10.3389/fbioe.2020.00917] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2020] [Accepted: 07/16/2020] [Indexed: 01/30/2023] Open
Abstract
The high viscosities/yield stresses of lignocellulose slurries makes their industrial processing a significant challenge. However, little is known regarding the degree to which liquefaction and its enzymatic requirements are specific to a substrate's physicochemical and rheological properties. In the work reported here, the substrate- and rheological regime-specificities of liquefaction of various substrates were assessed using real-time in-rheometer viscometry and offline oscillatory rheometry when hydrolyzed by combinations of cellobiohydrolase (Trichoderma reesei Cel7A), endoglucanase (Humicola insolens Cel45A), glycoside hydrolase (GH) family 10 xylanase, and GH family 11 xylanase. In contrast to previous work that has suggested that endoglucanase activity dominates enzymatic liquefaction, all of the enzymes were shown to have at least some liquefaction capacity depending on the substrate and reaction conditions. The contribution of individual enzymes was found to be influenced by the rheological regime; in the concentrated regime, the cellobiohydrolase outperformed the endoglucanase, achieving 2.4-fold higher yield stress reduction over the same timeframe, whereas the endoglucanase performed best in the semi-dilute regime. It was apparent that the significant differences in rheology and liquefaction mechanisms made it difficult to predict the liquefaction capacity of an enzyme or enzyme cocktail at different substrate concentrations.
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Affiliation(s)
- Timo van der Zwan
- Forest Products Biotechnology and Bioenergy Group, Department of Wood Science, Faculty of Forestry, The University of British Columbia, Vancouver, BC, Canada
| | - Alexander Sigg
- Forest Products Biotechnology and Bioenergy Group, Department of Wood Science, Faculty of Forestry, The University of British Columbia, Vancouver, BC, Canada
- Department of Chemistry, Technical University of Munich, Munich, Germany
| | - Jinguang Hu
- Forest Products Biotechnology and Bioenergy Group, Department of Wood Science, Faculty of Forestry, The University of British Columbia, Vancouver, BC, Canada
| | - Richard P. Chandra
- Forest Products Biotechnology and Bioenergy Group, Department of Wood Science, Faculty of Forestry, The University of British Columbia, Vancouver, BC, Canada
| | - Jack N. Saddler
- Forest Products Biotechnology and Bioenergy Group, Department of Wood Science, Faculty of Forestry, The University of British Columbia, Vancouver, BC, Canada
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2
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Kurašin M, Kuusk S, Kuusk P, Sørlie M, Väljamäe P. Slow Off-rates and Strong Product Binding Are Required for Processivity and Efficient Degradation of Recalcitrant Chitin by Family 18 Chitinases. J Biol Chem 2015; 290:29074-85. [PMID: 26468285 DOI: 10.1074/jbc.m115.684977] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2015] [Indexed: 12/18/2022] Open
Abstract
Processive glycoside hydrolases are the key components of enzymatic machineries that decompose recalcitrant polysaccharides, such as chitin and cellulose. The intrinsic processivity (P(Intr)) of cellulases has been shown to be governed by the rate constant of dissociation from polymer chain (koff). However, the reported koff values of cellulases are strongly dependent on the method used for their measurement. Here, we developed a new method for determining koff, based on measuring the exchange rate of the enzyme between a non-labeled and a (14)C-labeled polymeric substrate. The method was applied to the study of the processive chitinase ChiA from Serratia marcescens. In parallel, ChiA variants with weaker binding of the N-acetylglucosamine unit either in substrate-binding site -3 (ChiA-W167A) or the product-binding site +1 (ChiA-W275A) were studied. Both ChiA variants showed increased off-rates and lower apparent processivity on α-chitin. The rate of the production of insoluble reducing groups on the reduced α-chitin was an order of magnitude higher than koff, suggesting that the enzyme can initiate several processive runs without leaving the substrate. On crystalline chitin, the general activity of the wild type enzyme was higher, and the difference was magnifying with hydrolysis time. On amorphous chitin, the variants clearly outperformed the wild type. A model is proposed whereby strong interactions with polymer in the substrate-binding sites (low off-rates) and strong binding of the product in the product-binding sites (high pushing potential) are required for the removal of obstacles, like disintegration of chitin microfibrils.
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Affiliation(s)
| | - Silja Kuusk
- From the Institutes of Molecular and Cell Biology and
| | - Piret Kuusk
- Physics, University of Tartu, 51010 Tartu, Estonia and
| | - Morten Sørlie
- the Department of Chemistry, Biotechnology and Food Science, Norwegian University of Life Sciences, Ås 1432, Norway
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3
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Gonçalves GA, Takasugi Y, Jia L, Mori Y, Noda S, Tanaka T, Ichinose H, Kamiya N. Synergistic effect and application of xylanases as accessory enzymes to enhance the hydrolysis of pretreated bagasse. Enzyme Microb Technol 2015; 72:16-24. [DOI: 10.1016/j.enzmictec.2015.01.007] [Citation(s) in RCA: 75] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2014] [Revised: 12/16/2014] [Accepted: 01/19/2015] [Indexed: 11/30/2022]
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4
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Gourlay K, Hu J, Arantes V, Penttilä M, Saddler JN. The use of carbohydrate binding modules (CBMs) to monitor changes in fragmentation and cellulose fiber surface morphology during cellulase- and Swollenin-induced deconstruction of lignocellulosic substrates. J Biol Chem 2014; 290:2938-45. [PMID: 25527502 DOI: 10.1074/jbc.m114.627604] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
Although the actions of many of the hydrolytic enzymes involved in cellulose hydrolysis are relatively well understood, the contributions that amorphogenesis-inducing proteins might contribute to cellulose deconstruction are still relatively undefined. Earlier work has shown that disruptive proteins, such as the non-hydrolytic non-oxidative protein Swollenin, can open up and disaggregate the less-ordered regions of lignocellulosic substrates. Within the cellulosic fraction, relatively disordered, amorphous regions known as dislocations are known to occur along the length of the fibers. It was postulated that Swollenin might act synergistically with hydrolytic enzymes to initiate biomass deconstruction within these dislocation regions. Carbohydrate binding modules (CBMs) that preferentially bind to cellulosic substructures were fluorescently labeled. They were imaged, using confocal microscopy, to assess the distribution of crystalline and amorphous cellulose at the fiber surface, as well as to track changes in surface morphology over the course of enzymatic hydrolysis and fiber fragmentation. Swollenin was shown to promote targeted disruption of the cellulosic structure at fiber dislocations.
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Affiliation(s)
- Keith Gourlay
- From the Forest Products Biotechnology/Bioenergy Group, Department of Wood Science, Faculty of Forestry, University of British Columbia, Vancouver, British Columbia V6T 1Z4, Canada and
| | - Jinguang Hu
- From the Forest Products Biotechnology/Bioenergy Group, Department of Wood Science, Faculty of Forestry, University of British Columbia, Vancouver, British Columbia V6T 1Z4, Canada and
| | - Valdeir Arantes
- From the Forest Products Biotechnology/Bioenergy Group, Department of Wood Science, Faculty of Forestry, University of British Columbia, Vancouver, British Columbia V6T 1Z4, Canada and
| | - Merja Penttilä
- the VTT Technical Research Centre of Finland, Metallimiehenkuja 2 (Espoo), FI-02044 VTT, Finland
| | - Jack N Saddler
- From the Forest Products Biotechnology/Bioenergy Group, Department of Wood Science, Faculty of Forestry, University of British Columbia, Vancouver, British Columbia V6T 1Z4, Canada and
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5
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Yang D, Parlange JY, Walker LP. Cellulases Significantly Alter the Nano-Scale Reaction Space for Pretreated Lignocellulosic Biomass. Ind Biotechnol (New Rochelle N Y) 2014. [DOI: 10.1089/ind.2014.0028] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Affiliation(s)
- Dong Yang
- Department of Biological and Environmental Engineering, Cornell University, Ithaca, NY
| | - Jean-Yves Parlange
- Department of Biological and Environmental Engineering, Cornell University, Ithaca, NY
| | - Larry P. Walker
- Department of Biological and Environmental Engineering, Cornell University, Ithaca, NY
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6
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Yang D, Parlange JY, Walker LP. Revisiting size-exclusion chromatography for measuring structural changes in raw and pretreated mixed hardwoods and switchgrass. Biotechnol Bioeng 2014; 112:549-59. [PMID: 25212985 DOI: 10.1002/bit.25460] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2014] [Revised: 07/18/2014] [Accepted: 09/05/2014] [Indexed: 11/09/2022]
Abstract
The study of the biomass porous structure and its role in defining the accessibility of cell-wall-degrading enzymes (CWDEs) to the substrate is very important for understanding the cellulase-cellulose reaction system. Specific pore volume and specific surface area are two important measures of accessibility and a variety of methods have been used to make these measurements. For this study a size exclusion chromatography system was developed to measure specific pore volume and specific surface areas for raw and pretreated mixed-hardwood and switchgrass. Polyethylene glycol (PEG) probes of known molecular diameter (1.8-13 nm) were allowed to diffuse into the pore structure of the various biomass substrate packed in the column and subsequently eluted to generate high resolution concentration measurements with excellent reproducibility. Replicate measurements of probe concentrations from this system consistently yielded coefficient of variance of less than 1.5%. Our results showed that particle size reduction had a smaller influence on the specific pore volume distribution of raw mixed-hardwoods, whereas for switchgrass the larger particles yielded a significantly lower estimate for the pore volume distribution compared to the smaller particles. Our results also clearly showed that our bi-phasic pretreatment yielded the largest increase in pore volume accessibility for mixed-hardwoods relative to switchgrass. From these results a pore size change mechanism was proposed that could explain the influence of size reduction and pretreatment on pore volume measurements.
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Affiliation(s)
- Dong Yang
- Department of Biological and Environmental Engineering, Cornell University, Ithaca, New York, 14853
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7
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Luterbacher JS, Moran-Mirabal JM, Burkholder EW, Walker LP. Modeling enzymatic hydrolysis of lignocellulosic substrates using confocal fluorescence microscopy I: Filter paper cellulose. Biotechnol Bioeng 2014; 112:21-31. [DOI: 10.1002/bit.25329] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2014] [Revised: 05/08/2014] [Accepted: 06/30/2014] [Indexed: 11/09/2022]
Affiliation(s)
- Jeremy S. Luterbacher
- Department of Chemical and Biomolecular Engineering; Olin Hall; Cornell University; Ithaca New York
| | - Jose M. Moran-Mirabal
- Department of Chemistry and Chemical Biology; Arthur N. Bourns Science Building; McMaster University; Hamilton Ontario, Canada L8S4M1
| | - Eric W. Burkholder
- Department of Chemical and Biomolecular Engineering; Olin Hall; Cornell University; Ithaca New York
| | - Larry P. Walker
- Department of Biological and Environmental Engineering; Riley-Robb Hall; Cornell University; Ithaca New York 14850
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8
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Opitz B, Prediger A, Lüder C, Eckstein M, Hilterhaus L, Lindner P, Beutel S, Scheper T, Liese A. In Situ Microscopy for In-line Monitoring of the Enzymatic Hydrolysis of Cellulose. Anal Chem 2013; 85:8121-6. [DOI: 10.1021/ac4008495] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Britta Opitz
- Institute of Technical Biocatalysis, Hamburg University of Technology, Denickestrasse 15,
21073 Hamburg, Germany
| | - Andreas Prediger
- Institute
of Technical Chemistry, Gottfried Wilhelm Leibniz University Hanover, Callinstrasse
5, 30167 Hanover, Germany
| | - Christian Lüder
- Institute
of Technical Chemistry, Gottfried Wilhelm Leibniz University Hanover, Callinstrasse
5, 30167 Hanover, Germany
| | - Marrit Eckstein
- Evonik Industries AG, Goldschmidtstraße 100, 45127 Essen, Germany
| | - Lutz Hilterhaus
- Institute of Technical Biocatalysis, Hamburg University of Technology, Denickestrasse 15,
21073 Hamburg, Germany
| | - Patrick Lindner
- Institute
of Technical Chemistry, Gottfried Wilhelm Leibniz University Hanover, Callinstrasse
5, 30167 Hanover, Germany
| | - Sascha Beutel
- Institute
of Technical Chemistry, Gottfried Wilhelm Leibniz University Hanover, Callinstrasse
5, 30167 Hanover, Germany
| | - Thomas Scheper
- Institute
of Technical Chemistry, Gottfried Wilhelm Leibniz University Hanover, Callinstrasse
5, 30167 Hanover, Germany
| | - Andreas Liese
- Institute of Technical Biocatalysis, Hamburg University of Technology, Denickestrasse 15,
21073 Hamburg, Germany
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9
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Kostylev M, Wilson D. Two-parameter kinetic model based on a time-dependent activity coefficient accurately describes enzymatic cellulose digestion. Biochemistry 2013; 52:5656-64. [PMID: 23837567 DOI: 10.1021/bi400358v] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Lignocellulosic biomass is a potential source of renewable, low-carbon-footprint liquid fuels. Biomass recalcitrance and enzyme cost are key challenges associated with the large-scale production of cellulosic fuel. Kinetic modeling of enzymatic cellulose digestion has been complicated by the heterogeneous nature of the substrate and by the fact that a true steady state cannot be attained. We present a two-parameter kinetic model based on the Michaelis-Menten scheme ( Michaelis, L., and Menten, M. L. ( 1913 ) Biochem. Z. , 49 , 333 - 369 ) with a time-dependent activity coefficient analogous to fractal-like kinetics formulated by Kopelman ( Kopelman, R. ( 1988 ) Science 241 , 1620 - 1626 ). We provide a mathematical derivation and experimental support to show that one of the parameters is a total activity coefficient and the other is an intrinsic constant that reflects the ability of the cellulases to overcome substrate recalcitrance. The model is applicable to individual cellulases and their mixtures at low-to-medium enzyme loads. Using biomass degrading enzymes from cellulolytic bacterium Thermobifida fusca , we show that the model can be used for mechanistic studies of enzymatic cellulose digestion. We also demonstrate that it applies to the crude supernatant of the widely studied cellulolytic fungus Trichoderma reesei ; thus it can be used to compare cellulases from different organisms. The two parameters may serve a similar role to Vmax, KM, and kcat in classical kinetics. A similar approach may be applicable to other enzymes with heterogeneous substrates and where a steady state is not achievable.
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Affiliation(s)
- Maxim Kostylev
- Department of Molecular Biology and Genetics, 460 Biotechnology Building, Cornell University, Ithaca, NY 14853, USA.
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10
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Chauve M, Barre L, Tapin-Lingua S, Silva Perez DD, Decottignies D, Perez S, Ferreira NL. Evolution and impact of cellulose architecture during enzymatic hydrolysis by fungal cellulases. ACTA ACUST UNITED AC 2013. [DOI: 10.4236/abb.2013.412146] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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11
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Ye Z, Lane AN, Willing GA, Berson RE. Scaled-up separation of cellobiohydrolase1 from a cellulase mixture by ion-exchange chromatography. Biotechnol Prog 2011; 27:1644-52. [DOI: 10.1002/btpr.696] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2011] [Revised: 04/27/2011] [Indexed: 11/10/2022]
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12
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Park S, Baker JO, Himmel ME, Parilla PA, Johnson DK. Cellulose crystallinity index: measurement techniques and their impact on interpreting cellulase performance. BIOTECHNOLOGY FOR BIOFUELS 2010; 3:10. [PMID: 20497524 PMCID: PMC2890632 DOI: 10.1186/1754-6834-3-10] [Citation(s) in RCA: 1148] [Impact Index Per Article: 82.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/15/2009] [Accepted: 05/24/2010] [Indexed: 05/02/2023]
Abstract
Although measurements of crystallinity index (CI) have a long history, it has been found that CI varies significantly depending on the choice of measurement method. In this study, four different techniques incorporating X-ray diffraction and solid-state 13C nuclear magnetic resonance (NMR) were compared using eight different cellulose preparations. We found that the simplest method, which is also the most widely used, and which involves measurement of just two heights in the X-ray diffractogram, produced significantly higher crystallinity values than did the other methods. Data in the literature for the cellulose preparation used (Avicel PH-101) support this observation. We believe that the alternative X-ray diffraction (XRD) and NMR methods presented here, which consider the contributions from amorphous and crystalline cellulose to the entire XRD and NMR spectra, provide a more accurate measure of the crystallinity of cellulose. Although celluloses having a high amorphous content are usually more easily digested by enzymes, it is unclear, based on studies published in the literature, whether CI actually provides a clear indication of the digestibility of a cellulose sample. Cellulose accessibility should be affected by crystallinity, but is also likely to be affected by several other parameters, such as lignin/hemicellulose contents and distribution, porosity, and particle size. Given the methodological dependency of cellulose CI values and the complex nature of cellulase interactions with amorphous and crystalline celluloses, we caution against trying to correlate relatively small changes in CI with changes in cellulose digestibility. In addition, the prediction of cellulase performance based on low levels of cellulose conversion may not include sufficient digestion of the crystalline component to be meaningful.
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Affiliation(s)
- Sunkyu Park
- Biosciences Center, National Renewable Energy Laboratory, 1617 Cole Blvd, Golden, CO 80401, USA
- Department of Forest Biomaterials, North Carolina State University, Raleigh, NC 27695, USA
| | - John O Baker
- Biosciences Center, National Renewable Energy Laboratory, 1617 Cole Blvd, Golden, CO 80401, USA
| | - Michael E Himmel
- Biosciences Center, National Renewable Energy Laboratory, 1617 Cole Blvd, Golden, CO 80401, USA
| | - Philip A Parilla
- National Center for Photovoltaics, National Renewable Energy Laboratory, 1617 Cole Blvd, Golden, CO 80401, USA
| | - David K Johnson
- Biosciences Center, National Renewable Energy Laboratory, 1617 Cole Blvd, Golden, CO 80401, USA
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13
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Caspi J, Irwin D, Lamed R, Shoham Y, Fierobe HP, Wilson DB, Bayer EA. Thermobifida fuscafamily-6 cellulases as potential designer cellulosome components. BIOCATAL BIOTRANSFOR 2009. [DOI: 10.1080/10242420600598046] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
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14
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Gama FM, Mota M. Enzymatic Hydrolysis of Cellulose (I): Relationship between Kinetics and Physico-Chemical Parameters. BIOCATAL BIOTRANSFOR 2009. [DOI: 10.3109/10242429709103511] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
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15
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Caspi J, Irwin D, Lamed R, Li Y, Fierobe HP, Wilson DB, Bayer EA. Conversion of Thermobifida fusca free exoglucanases into cellulosomal components: comparative impact on cellulose-degrading activity. J Biotechnol 2008; 135:351-7. [PMID: 18582975 DOI: 10.1016/j.jbiotec.2008.05.003] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2007] [Revised: 04/30/2008] [Accepted: 05/08/2008] [Indexed: 11/26/2022]
Abstract
Cellulosomes are multi-enzyme complexes produced by certain anaerobic bacteria that exhibit efficient degradation of plant cell wall polysaccharides. To understand their enhanced levels of hydrolysis, we are investigating the effects of converting a free-cellulase system into a cellulosomal one. To achieve this end, we are replacing the cellulose-binding module of the native cellulases, produced by the aerobic bacterium Thermobifida fusca, with a cellulosome-derived dockerin module of established specificity, to allow their incorporation into defined "designer cellulosomes". In this communication, we have attached divergent dockerins to the two exoglucanases produced by T. fusca exoglucanase, Cel6B and Cel48A. The resultant fusion proteins were shown to bind efficiently and specifically to their matching cohesins, and their activities on several different cellulose substrates were compared. The lack of a cellulose-binding module in Cel6B had a deleterious effect on its activity on crystalline substrates. In contrast, the dockerin-bearing family-48 exoglucanase showed increased levels of hydrolytic activity on carboxymethyl cellulose and on both crystalline substrates tested, compared to the wild-type enzyme. The marked difference in the response of the two exoglucanases to incorporation into a cellulosome, suggests that the family-48 cellulase is more appropriate than the family-6 enzyme as a designer cellulosome component.
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Affiliation(s)
- Jonathan Caspi
- Department of Biological Chemistry, The Weizmann Institute of Science, 26 Herzl Street, Rehovot 76100, Israel
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16
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Percival Zhang YH, Himmel ME, Mielenz JR. Outlook for cellulase improvement: screening and selection strategies. Biotechnol Adv 2006; 24:452-81. [PMID: 16690241 DOI: 10.1016/j.biotechadv.2006.03.003] [Citation(s) in RCA: 663] [Impact Index Per Article: 36.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2006] [Revised: 03/06/2006] [Accepted: 03/11/2006] [Indexed: 10/24/2022]
Abstract
Cellulose is the most abundant renewable natural biological resource, and the production of biobased products and bioenergy from less costly renewable lignocellulosic materials is important for the sustainable development of human beings. A reduction in cellulase production cost, an improvement in cellulase performance, and an increase in sugar yields are all vital to reduce the processing costs of biorefineries. Improvements in specific cellulase activities for non-complexed cellulase mixtures can be implemented through cellulase engineering based on rational design or directed evolution for each cellulase component enzyme, as well as on the reconstitution of cellulase components. Here, we review quantitative cellulase activity assays using soluble and insoluble substrates, and focus on their advantages and limitations. Because there are no clear relationships between cellulase activities on soluble substrates and those on insoluble substrates, soluble substrates should not be used to screen or select improved cellulases for processing relevant solid substrates, such as plant cell walls. Cellulase improvement strategies based on directed evolution using screening on soluble substrates have been only moderately successful, and have primarily targeted improvement in thermal tolerance. Heterogeneity of insoluble cellulose, unclear dynamic interactions between insoluble substrate and cellulase components, and the complex competitive and/or synergic relationship among cellulase components limit rational design and/or strategies, depending on activity screening approaches. Herein, we hypothesize that continuous culture using insoluble cellulosic substrates could be a powerful selection tool for enriching beneficial cellulase mutants from the large library displayed on the cell surface.
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Affiliation(s)
- Y-H Percival Zhang
- Biological Systems Engineering Department, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061, USA.
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17
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Zhang YHP, Lynd LR. Toward an aggregated understanding of enzymatic hydrolysis of cellulose: noncomplexed cellulase systems. Biotechnol Bioeng 2005; 88:797-824. [PMID: 15538721 DOI: 10.1002/bit.20282] [Citation(s) in RCA: 883] [Impact Index Per Article: 46.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Information pertaining to enzymatic hydrolysis of cellulose by noncomplexed cellulase enzyme systems is reviewed with a particular emphasis on development of aggregated understanding incorporating substrate features in addition to concentration and multiple cellulase components. Topics considered include properties of cellulose, adsorption, cellulose hydrolysis, and quantitative models. A classification scheme is proposed for quantitative models for enzymatic hydrolysis of cellulose based on the number of solubilizing activities and substrate state variables included. We suggest that it is timely to revisit and reinvigorate functional modeling of cellulose hydrolysis, and that this would be highly beneficial if not necessary in order to bring to bear the large volume of information available on cellulase components on the primary applications that motivate interest in the subject.
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18
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Genetics and Properties of Cellulases. ADVANCES IN BIOCHEMICAL ENGINEERING/BIOTECHNOLOGY 2001. [DOI: 10.1007/3-540-49194-5_1] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/13/2023]
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19
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Driskill LE, Bauer MW, Kelly RM. Synergistic interactions among ?-laminarinase, ?-1,4-glucanase, and ?-glucosidase from the hyperthermophilic archaeonPyrococcus furiosus during hydrolysis of ?-1,4-, ?-1,3-, and mixed-linked polysaccharides. Biotechnol Bioeng 1999. [DOI: 10.1002/(sici)1097-0290(1999)66:1<51::aid-bit5>3.0.co;2-k] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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20
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Hydrolysis of cellulose using ternary mixtures of purified celluloses. Appl Biochem Biotechnol 1998; 70-72:395-403. [DOI: 10.1007/bf02920154] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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21
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22
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Gupte A, Madamwar D. Production of cellulolytic enzymes by coculturing ofAspergillus ellipticus andAspergillus fumigatus grown on bagasse under solid state fermentation. Appl Biochem Biotechnol 1997. [DOI: 10.1007/bf02788002] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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23
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Gama F, Carvalho M, Figueiredo M, Mota M. Comparative study of cellulose fragmentation by enzymes and ultrasound. Enzyme Microb Technol 1997. [DOI: 10.1016/s0141-0229(96)00076-2] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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24
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Galas E, Pyc R, Romanowska I. Hydrolysis and transformation of cellulose withAspergillus niger IBT-90 enzymes. ACTA ACUST UNITED AC 1997. [DOI: 10.1002/abio.370170410] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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25
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Lao G, Wilson DB. Cloning, sequencing, and expression of a Thermomonospora fusca protease gene in Streptomyces lividans. Appl Environ Microbiol 1996; 62:4256-9. [PMID: 8900021 PMCID: PMC168250 DOI: 10.1128/aem.62.11.4256-4259.1996] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
The major Thermomonospora fusca YX extracellular protease gene (tfpA) was cloned into Escherichia coli and Streptomyces lividans and was sequenced. The open reading frame encoded 375 residues, including a 31-residue potential signal sequence, an N-terminal prosequence containing 150 residues, and the 194-residue mature protease that belongs to the chymotrypsin family. The protease was secreted by S. lividans, but evidence suggested that it was bound to an extracellular protease inhibitor. An inhibitor-deficient mutant was selected to produce protease for purification.
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Affiliation(s)
- G Lao
- Department of Microbiology, Cornell University, Ithaca, New York 14853, USA
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Abstract
Microorganisms are efficient degraders of starch, chitin, and the polysaccharides in plant cell walls. Attempts to purify hydrolases led to the realization that a microorganism may produce a multiplicity of enzymes, referred to as a system, for the efficient utilization of a polysaccharide. In order to fully characterize a particular enzyme, it must be obtained free of the other components of a system. Quite often, this proves to be very difficult because of the complexity of a system. This realization led to the cloning of the genes encoding them as an approach to eliminating other components. More than 400 such genes have been cloned and sequenced, and the enzymes they encode have been grouped into more than 50 families of related amino acid sequences. The enzyme systems revealed in this manner are complex on two quite different levels. First, many of the individual enzymes are complex, as they are modular proteins comprising one or more catalytic domains linked to ancillary domains that often include one or more substrate-binding domains. Second, the systems are complex, comprising from a few to 20 or more enzymes, all of which hydrolyze a particular substrate. Systems for the hydrolysis of plant cell walls usually contain more components than systems for the hydrolysis of starch and chitin because the cell walls contain several polysaccharides. In general, the systems produced by different microorganisms for the hydrolysis of a particular polysaccharide comprise similar enzymes from the same families.
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Affiliation(s)
- R A Warren
- Department of Microbiology and Immunology, University of British Columbia, Vancouver, Canada
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Baker JO, Adney WS, Nleves RA, Thomas SR, Wilson DB, Himmel ME. A new thermostable endoglucanase,Acidothermus cellulolyticus E1. Appl Biochem Biotechnol 1994. [DOI: 10.1007/bf02941803] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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28
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Abstract
Cellulolytic microorganisms play an important role in the biosphere by recycling cellulose, the most abundant carbohydrate produced by plants. Cellulose is a simple polymer, but it forms insoluble, crystalline microfibrils, which are highly resistant to enzymatic hydrolysis. All organisms known to degrade cellulose efficiently produce a battery of enzymes with different specificities, which act together in synergism. The study of cellulolytic enzymes at the molecular level has revealed some of the features that contribute to their activity. In spite of a considerable diversity, sequence comparisons show that the catalytic cores of cellulases belong to a restricted number of families. Within each family, available data suggest that the various enzymes share a common folding pattern, the same catalytic residues, and the same reaction mechanism, i.e. either single substitution with inversion of configuration or double substitution resulting in retention of the beta-configuration at the anomeric carbon. An increasing number of three-dimensional structures is becoming available for cellulases and xylanases belonging to different families, which will provide paradigms for molecular modeling of related enzymes. In addition to catalytic domains, many cellulolytic enzymes contain domains not involved in catalysis, but participating in substrate binding, multi-enzyme complex formation, or possibly attachment to the cell surface. Presumably, these domains assist in the degradation of crystalline cellulose by preventing the enzymes from being washed off from the surface of the substrate, by focusing hydrolysis on restricted areas in which the substrate is synergistically destabilized by multiple cutting events, and by facilitating recovery of the soluble degradation products by the cellulolytic organism. In most cellulolytic organisms, cellulase synthesis is repressed in the presence of easily metabolized, soluble carbon sources and induced in the presence of cellulose. Induction of cellulases appears to be effected by soluble products generated from cellulose by cellulolytic enzymes synthesized constitutively at a low level. These products are presumably converted into true inducers by transglycosylation reactions. Several applications of cellulases or hemicellulases are being developed for textile, food, and paper pulp processing. These applications are based on the modification of cellulose and hemicellulose by partial hydrolysis. Total hydrolysis of cellulose into glucose, which could be fermented into ethanol, isopropanol or butanol, is not yet economically feasible. However, the need to reduce emissions of greenhouse gases provides an added incentive for the development of processes generating fuels from cellulose, a major renewable carbon source.
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Affiliation(s)
- P Béguin
- Unité de Physiologie Cellulaire, Département des Biotechnologies, Institut Pasteur, Paris, France
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29
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Xin LZ, Kumakura M. New immobilization method of filamentous cells with thin paper carrier surfaces modified by radiation. METHODS IN MICROBIOLOGY 1994. [DOI: 10.1016/0167-7012(94)90023-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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30
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Walker LP, Belair CD, Wilson DB, Irwin DC. Engineering cellulase mixtures by varying the mole fraction ofThermomonospora fusca E5 and E3,Trichoderma reesei CBHI, andCaldocellum saccharolyticum ?-glucosidase. Biotechnol Bioeng 1993; 42:1019-28. [DOI: 10.1002/bit.260420902] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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31
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Activity studies of eight purified cellulases: Specificity, synergism, and binding domain effects. Biotechnol Bioeng 1993; 42:1002-13. [DOI: 10.1002/bit.260420811] [Citation(s) in RCA: 270] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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32
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McGinnis K, Wilson DB. Disulfide arrangement and functional domains of beta-1,4-endoglucanse E5 from Thermomonospora fusca. Biochemistry 1993; 32:8157-61. [PMID: 8347615 DOI: 10.1021/bi00083a015] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Thermomonospora fusca cellulase E5 contains six cysteine residues. The number and location of the disulfide bonds and the effect of reduction of the disulfides and modification of the resulting half-cystine residues on enzymatic activity were determined. No free sulfhydryl groups were found in E5. Reduction and subsequent labeling with iodoacetamide of E5 and of an enzymatically active 32-kDa proteolytic derivative of E5 (E5cd) showed that one of the three disulfides is accessible to reduction under nondenatured conditions while the other two are not accessible. Full reduction of the disulfides and complete carboxymethylation of the six cysteines decrease the specific activity of E5 on CMC by more than half, but reduction of only the exposed disulfide bond does not affect enzymatic activity or binding of E5 to cellulose. A 14-kDa proteolytic fragment of E5 containing 120 amino acids from the N-terminus of the protein was shown to bind to crystalline cellulose. This confirms earlier evidence that the cellulose binding domain of E5 is located at the N-terminus of the protein. This 14-kDa fragment contains the accessible disulfide bond involving Cys93 and Cys100. The location of the two disulfide bonds in the other fragment (E5cd) was determined by cleaving it with cyanogen bromide under conditions that left the disulfide bonds intact. The resulting peptides were separated under both nonreducing and reducing conditions using RP-HPLC. Amino acid analysis of peptide peaks indicated that one disulfide linkage in E5cd joins Cys138 to Cys143 while the other joins Cys166 to Cys406.
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Affiliation(s)
- K McGinnis
- Section of Biochemistry, Molecular, and Cell Biology, Cornell University, Ithaca, New York 14853
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33
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McGinnis K, Kroupis C, Wilson DB. Dimerization of Thermomonospora fusca beta-1,4-endoglucanase E2. Biochemistry 1993; 32:8146-50. [PMID: 8347613 DOI: 10.1021/bi00083a013] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Unboiled Thermomonospora fusca endoglucanase E2 electrophoresed on SDS-polyacrylamide gels migrated in the range of 80-90 kDa, but when boiled it migrated in the 40-42-kDa range. Sedimentation equilibrium centrifugation as well as chemical cross-linking experiments confirmed that E2 is a dimer. The dimer was reversibly dissociated at low pH. The E2 dimer was stable up to 70 degrees C, but began to dissociate at this temperature after a 30-60-min incubation. A nondimerizing mutant was obtained using region-specific chemical mutagenesis. DNA sequencing of this mutant revealed a single base change that substituted Gly for Glu-263. Chemical modification of carboxylic acid residues in E2 disrupted the dimer interaction.
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Affiliation(s)
- K McGinnis
- Section of Biochemistry, Molecular, and Cell Biology, Cornell University, Ithaca, New York 14853
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34
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McGinnis K, Wilson DB. Disulfide arrangement and chemical modification of beta-1,4-endoglucanase E2 from Thermomonospora fusca. Biochemistry 1993; 32:8151-6. [PMID: 8347614 DOI: 10.1021/bi00083a014] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Thermomonospora fusca endoglucanase E2 contains six cysteine residues scattered along the protein sequence. Four of the cysteine residues were shown to participate in two disulfide bonds while the last two form a third disulfide bond. Neither full reduction of the disulfides nor complete carboxymethylation of all six cysteines totally destroys enzymatic activity, but the activity of the reduced enzyme is much lower than the native enzyme and the iodoacetamide-modified enzyme has very low activity. Reduction of only the accessible disulfides drastically decreases the enzyme's thermostability. One disulfide linkage joins Cys80 to Cys125, another joins Cys232 to Cys267, and the third joins Cys315 to Cys407. The first two bonds are similar to those in cellobiohydrolase II, which also belongs to cellulase family B (Rouvinen et al., 1990; Lao et al., 1991; Henrissat et al., 1989). Direct evidence for the involvement of carboxyl groups in catalysis by E2 was demonstrated by chemical modification with carbodiimide.
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Affiliation(s)
- K McGinnis
- Section of Biochemistry, Molecular, and Cell Biology, Cornell University, Ithaca, New York 14853
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