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Chen M, Ropartz D, Mac-Béar J, Bonnin E, Lahaye M. New insight into the mode of action of a GH74 xyloglucanase on tamarind seed xyloglucan: Action pattern and cleavage site. Carbohydr Res 2022; 521:108661. [DOI: 10.1016/j.carres.2022.108661] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2022] [Revised: 06/28/2022] [Accepted: 08/23/2022] [Indexed: 11/26/2022]
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2
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Biswal AK, Hengge NN, Black IM, Atmodjo MA, Mohanty SS, Ryno D, Himmel ME, Azadi P, Bomble YJ, Mohnen D. Composition and yield of non-cellulosic and cellulosic sugars in soluble and particulate fractions during consolidated bioprocessing of poplar biomass by Clostridium thermocellum. BIOTECHNOLOGY FOR BIOFUELS AND BIOPRODUCTS 2022; 15:23. [PMID: 35227303 PMCID: PMC8887089 DOI: 10.1186/s13068-022-02119-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/19/2021] [Accepted: 02/10/2022] [Indexed: 06/14/2023]
Abstract
BACKGROUND Terrestrial plant biomass is the primary renewable carbon feedstock for enabling transition to a sustainable bioeconomy. Consolidated bioprocessing (CBP) by the cellulolytic thermophile Clostridium thermocellum offers a single step microbial platform for production of biofuels and biochemicals via simultaneous solubilization of carbohydrates from lignocellulosic biomass and conversion to products. Here, solubilization of cell wall cellulosic, hemicellulosic, and pectic polysaccharides in the liquor and solid residues generated during CBP of poplar biomass by C. thermocellum was analyzed. RESULTS The total amount of biomass solubilized in the C. thermocellum DSM1313 fermentation platform was 5.8, 10.3, and 13.7% of milled non-pretreated poplar after 24, 48, and 120 h, respectively. These results demonstrate solubilization of 24% cellulose and 17% non-cellulosic sugars after 120 h, consistent with prior reports. The net solubilization of non-cellulosic sugars by C. thermocellum (after correcting for the uninoculated control fermentations) was 13 to 36% of arabinose (Ara), xylose (Xyl), galactose (Gal), mannose (Man), and glucose (Glc); and 15% and 3% of fucose and glucuronic acid, respectively. No rhamnose was solubilized and 71% of the galacturonic acid (GalA) was solubilized. These results indicate that C. thermocellum may be selective for the types and/or rate of solubilization of the non-cellulosic wall polymers. Xyl, Man, and Glc were found to accumulate in the fermentation liquor at levels greater than in uninoculated control fermentations, whereas Ara and Gal did not accumulate, suggesting that C. thermocellum solubilizes both hemicelluloses and pectins but utilizes them differently. After five days of fermentation, the relative amount of Rha in the solid residues increased 21% indicating that the Rha-containing polymer rhamnogalacturonan I (RG-I) was not effectively solubilized by C. thermocellum CBP, a result confirmed by immunoassays. Comparison of the sugars in the liquor versus solid residue showed that C. thermocellum solubilized hemicellulosic xylan and mannan, but did not fully utilize them, solubilized and appeared to utilize pectic homogalacturonan, and did not solubilize RG-I. CONCLUSIONS The significant relative increase in RG-I in poplar solid residues following CBP indicates that C. thermocellum did not solubilize RG-I. These results support the hypothesis that this pectic glycan may be one barrier for efficient solubilization of poplar by C. thermocellum.
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Affiliation(s)
- Ajaya K. Biswal
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, GA 30602 USA
- Complex Carbohydrate Research Center, University of Georgia, 315 Riverbend Rd, Athens, GA 30602 USA
| | - Neal N. Hengge
- Biosciences Center, National Renewable Energy Laboratory, Golden, CO 80401 USA
| | - Ian M. Black
- Complex Carbohydrate Research Center, University of Georgia, 315 Riverbend Rd, Athens, GA 30602 USA
| | - Melani A. Atmodjo
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, GA 30602 USA
- Complex Carbohydrate Research Center, University of Georgia, 315 Riverbend Rd, Athens, GA 30602 USA
| | - Sushree S. Mohanty
- Complex Carbohydrate Research Center, University of Georgia, 315 Riverbend Rd, Athens, GA 30602 USA
| | - David Ryno
- Complex Carbohydrate Research Center, University of Georgia, 315 Riverbend Rd, Athens, GA 30602 USA
| | - Michael E. Himmel
- Biosciences Center, National Renewable Energy Laboratory, Golden, CO 80401 USA
| | - Parastoo Azadi
- Complex Carbohydrate Research Center, University of Georgia, 315 Riverbend Rd, Athens, GA 30602 USA
| | - Yannick J. Bomble
- Biosciences Center, National Renewable Energy Laboratory, Golden, CO 80401 USA
| | - Debra Mohnen
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, GA 30602 USA
- Complex Carbohydrate Research Center, University of Georgia, 315 Riverbend Rd, Athens, GA 30602 USA
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3
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Ahmed J, Kumar K, Sharma K, Fontes CMGA, Goyal A. Computational and SAXS-based structure insights of pectin acetyl esterase ( CtPae12B) of family 12 carbohydrate esterase from Clostridium thermocellum ATCC 27405. J Biomol Struct Dyn 2021; 40:8437-8454. [PMID: 33860720 DOI: 10.1080/07391102.2021.1911858] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Abstract
Pectin is a complex form of polysaccharide and is composed of several structural components that require the concerted action of several pectinases for its complete degradation. In this study, in silico and solution structure of a pectin acetyl esterase (CtPae12B) of family 12 carbohydrate esterase (CE12) from Clostridium thermocellum was determined. The CtPae12B modelled structure, showed a new α/β hydrolase fold, similar to the fold found in the crystal structures of its nearest homologues from CE12 family, which differed from α/β hydrolase fold found in glycoside hydrolases. In the active site of CtPae12B, two loops (loop1 and loop6) play an important role in the formation of a catalytic triad Ser15-Asp187-His190, where Ser15 acts as a nucleophile. The structural stability of CtPae12B and its catalytic site was detected by performing molecular dynamic (MD) simulation which showed stable and compact conformation of the structure. Molecular docking method was employed to analyse the conformations of various suitable ligands docked at the active site of CtPae12B. The stability and structural specificity of the catalytic residues with the ligand, 4-nitrophenyl acetate (4-NPA) was confirmed by MD simulation of CtPae12B-4NPA docked complex. Moreover, it was found that the nucleophile Ser15, forms hydrophobic interaction with 4-NPA in the active site to complete covalent catalysis. Small angle X-ray scattering analysis of CtPae12B at 3 mg/mL displayed elongated, compact and monodispersed nature in solution. The ab initio derived dummy model showed that CtPae12B exists as a homotrimer at 3 mg/mL which was also confirmed by dynamic light scattering.Communicated by Ramaswamy H. Sarma.
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Affiliation(s)
- Jebin Ahmed
- Carbohydrate Enzyme Biotechnology Laboratory, Department of Biosciences and Bioengineering, Indian Institute of Technology Guwahati, Guwahati, Assam, India
| | - Krishan Kumar
- Carbohydrate Enzyme Biotechnology Laboratory, Department of Biosciences and Bioengineering, Indian Institute of Technology Guwahati, Guwahati, Assam, India
| | - Kedar Sharma
- Carbohydrate Enzyme Biotechnology Laboratory, Department of Biosciences and Bioengineering, Indian Institute of Technology Guwahati, Guwahati, Assam, India.,Laboratory of Small Molecules & Macro Molecular Crystallography at Department of Bioengineering, Indian Institute of Technology Gandhinagar, Gandhinagar, India
| | - Carlos M G A Fontes
- CIISA - Faculdade de Medicina Veterinária, Universidade de Lisboa, Avenida da Universidade Técnica, Lisbon, Portugal.,NZYTech - Genes & Enzymes, Estrada do Paço do Lumiar, Lisbon, Portugal
| | - Arun Goyal
- Carbohydrate Enzyme Biotechnology Laboratory, Department of Biosciences and Bioengineering, Indian Institute of Technology Guwahati, Guwahati, Assam, India
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4
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Role of extremophiles and their extremozymes in biorefinery process of lignocellulose degradation. Extremophiles 2021; 25:203-219. [PMID: 33768388 DOI: 10.1007/s00792-021-01225-0] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2020] [Accepted: 03/10/2021] [Indexed: 12/20/2022]
Abstract
Technological advances in the field of life sciences have led to discovery of organisms that live in harsh environmental conditions referred to as extremophiles. These organisms have adapted themselves to thrive in extreme habitat giving these organisms an advantage over conventional mesophilic organisms in various industrial applications. Extremozymes produced by these extremophiles have high tolerance to inhospitable environmental conditions making them an ideal enzyme system for various industrial processes. A notable application of these extremophiles and extremozymes is their use in the degradation of recalcitrant lignocellulosic biomass and application in biorefineries. For maximum utilization of the trapped carbon source from this obstinate biomass, pretreatment is a necessary step that requires various physiochemical and enzymatic treatments. From search for novel extremophiles and extremozymes to development of various genetic and protein engineering techniques, investigation on extremozymes with enhanced stability and efficiency is been done. Since extremozymes are easily calibrated to work under such conditions, they have become an emerging topic in the research field of biofuel production. The review discusses the various extremozymes that play an important role in lignocellulose degradation along with recent studies on their molecular and genetic evolution for industrial application and production of biofuels and various value-added products.
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Zavyalov AV, Rykov SV, Lunina NA, Sushkova VI, Yarotsky SV, Berezina OV. Plant Polysaccharide Xyloglucan and Enzymes That Hydrolyze It (Review). RUSSIAN JOURNAL OF BIOORGANIC CHEMISTRY 2020. [DOI: 10.1134/s1068162019070148] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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6
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Arnal G, Stogios PJ, Asohan J, Attia MA, Skarina T, Viborg AH, Henrissat B, Savchenko A, Brumer H. Substrate specificity, regiospecificity, and processivity in glycoside hydrolase family 74. J Biol Chem 2019; 294:13233-13247. [PMID: 31324716 DOI: 10.1074/jbc.ra119.009861] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2019] [Revised: 07/16/2019] [Indexed: 12/11/2022] Open
Abstract
Glycoside hydrolase family 74 (GH74) is a historically important family of endo-β-glucanases. On the basis of early reports of detectable activity on cellulose and soluble cellulose derivatives, GH74 was originally considered to be a "cellulase" family, although more recent studies have generally indicated a high specificity toward the ubiquitous plant cell wall matrix glycan xyloglucan. Previous studies have indicated that GH74 xyloglucanases differ in backbone cleavage regiospecificities and can adopt three distinct hydrolytic modes of action: exo, endo-dissociative, and endo-processive. To improve functional predictions within GH74, here we coupled in-depth biochemical characterization of 17 recombinant proteins with structural biology-based investigations in the context of a comprehensive molecular phylogeny, including all previously characterized family members. Elucidation of four new GH74 tertiary structures, as well as one distantly related dual seven-bladed β-propeller protein from a marine bacterium, highlighted key structure-function relationships along protein evolutionary trajectories. We could define five phylogenetic groups, which delineated the mode of action and the regiospecificity of GH74 members. At the extremes, a major group of enzymes diverged to hydrolyze the backbone of xyloglucan nonspecifically with a dissociative mode of action and relaxed backbone regiospecificity. In contrast, a sister group of GH74 enzymes has evolved a large hydrophobic platform comprising 10 subsites, which facilitates processivity. Overall, the findings of our study refine our understanding of catalysis in GH74, providing a framework for future experimentation as well as for bioinformatics predictions of sequences emerging from (meta)genomic studies.
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Affiliation(s)
- Gregory Arnal
- Michael Smith Laboratories, University of British Columbia, 2185 East Mall, Vancouver, British Columbia V6T 1Z4, Canada
| | - Peter J Stogios
- Department of Chemical Engineering and Applied Chemistry, University of Toronto, Toronto, Ontario M5S 3E5, Canada
| | - Jathavan Asohan
- Michael Smith Laboratories, University of British Columbia, 2185 East Mall, Vancouver, British Columbia V6T 1Z4, Canada
| | - Mohamed A Attia
- Michael Smith Laboratories, University of British Columbia, 2185 East Mall, Vancouver, British Columbia V6T 1Z4, Canada; Department of Chemistry, University of British Columbia, Vancouver, British Columbia V6T 1Z1, Canada
| | - Tatiana Skarina
- Department of Chemical Engineering and Applied Chemistry, University of Toronto, Toronto, Ontario M5S 3E5, Canada
| | - Alexander Holm Viborg
- Michael Smith Laboratories, University of British Columbia, 2185 East Mall, Vancouver, British Columbia V6T 1Z4, Canada
| | - Bernard Henrissat
- Architecture et Fonction des Macromolécules Biologiques (AFMB), CNRS, Aix-Marseille University, 13007 Marseille, France; INRA, USC1408 Architecture et Fonction des Macromolécules Biologiques (AFMB), 13007 Marseille, France
| | - Alexei Savchenko
- Department of Chemical Engineering and Applied Chemistry, University of Toronto, Toronto, Ontario M5S 3E5, Canada; Department of Microbiology, Immunology and Infectious Diseases, University of Calgary, Calgary, Alberta T2N 4N1, Canada.
| | - Harry Brumer
- Michael Smith Laboratories, University of British Columbia, 2185 East Mall, Vancouver, British Columbia V6T 1Z4, Canada; Department of Chemistry, University of British Columbia, Vancouver, British Columbia V6T 1Z1, Canada; Department of Biochemistry and Molecular Biology, University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada; Department of Botany, University of British Columbia, Vancouver, British Columbia V6T 1Z4, Canada.
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7
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Discovery of a Thermostable GH10 Xylanase with Broad Substrate Specificity from the Arctic Mid-Ocean Ridge Vent System. Appl Environ Microbiol 2019; 85:AEM.02970-18. [PMID: 30635385 DOI: 10.1128/aem.02970-18] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2018] [Accepted: 01/03/2019] [Indexed: 11/20/2022] Open
Abstract
A two-domain GH10 xylanase-encoding gene (amor_gh10a) was discovered from a metagenomic data set, generated after in situ incubation of a lignocellulosic substrate in hot sediments on the sea floor of the Arctic Mid-Ocean Ridge (AMOR). AMOR_GH10A comprises a signal peptide, a carbohydrate-binding module belonging to a previously uncharacterized family, and a catalytic glycosyl hydrolase (GH10) domain. The enzyme shares the highest sequence identity (42%) with a hypothetical protein from a Verrucomicrobia bacterium, and its GH10 domain shares low identity (24 to 28%) with functionally characterized xylanases. Purified AMOR_GH10A showed thermophilic and halophilic properties and was active toward various xylans. Uniquely, the enzyme showed high activity toward amorphous cellulose, glucomannan, and xyloglucan and was more active toward cellopentaose than toward xylopentaose. Binding assays showed that the N-terminal domain of this broad-specificity GH10 binds strongly to amorphous cellulose, as well as to microcrystalline cellulose, birchwood glucuronoxylan, barley β-glucan, and konjac glucomannan, confirming its classification as a novel CBM (CBM85).IMPORTANCE Hot springs at the sea bottom harbor unique biodiversity and are a promising source of enzymes with interesting properties. We describe the functional characterization of a thermophilic and halophilic multidomain xylanase originating from the Arctic Mid-Ocean Ridge vent system, belonging to the well-studied family 10 of glycosyl hydrolases (GH10). This xylanase, AMOR_GH10A, has a surprisingly wide substrate range and is more active toward cellopentaose than toward xylopentaose. This substrate promiscuity is unique for the GH10 family and could prove useful in industrial applications. Emphasizing the versatility of AMOR_GH10A, its N-terminal domain binds to both xylans and glycans, while not showing significant sequence similarities to any known carbohydrate-binding module (CBM) in the CAZy database. Thus, this N-terminal domain lays the foundation for the new CBM85 family.
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8
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Kunath BJ, Delogu F, Naas AE, Arntzen MØ, Eijsink VGH, Henrissat B, Hvidsten TR, Pope PB. From proteins to polysaccharides: lifestyle and genetic evolution of Coprothermobacter proteolyticus. THE ISME JOURNAL 2019; 13:603-617. [PMID: 30315317 PMCID: PMC6461833 DOI: 10.1038/s41396-018-0290-y] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/13/2018] [Revised: 07/11/2018] [Accepted: 09/19/2018] [Indexed: 11/29/2022]
Abstract
Microbial communities that degrade lignocellulosic biomass are typified by high levels of species- and strain-level complexity, as well as synergistic interactions between both cellulolytic and non-cellulolytic microorganisms. Coprothermobacter proteolyticus frequently dominates thermophilic, lignocellulose-degrading communities with wide geographical distribution, which is in contrast to reports that it ferments proteinaceous substrates and is incapable of polysaccharide hydrolysis. Here we deconvolute a highly efficient cellulose-degrading consortium (SEM1b) that is co-dominated by Clostridium (Ruminiclostridium) thermocellum and multiple heterogenic strains affiliated to C. proteolyticus. Metagenomic analysis of SEM1b recovered metagenome-assembled genomes (MAGs) for each constituent population, whereas in parallel two novel strains of C. proteolyticus were successfully isolated and sequenced. Annotation of all C. proteolyticus genotypes (two strains and one MAG) revealed their genetic acquisition of carbohydrate-active enzymes (CAZymes), presumably derived from horizontal gene transfer (HGT) events involving polysaccharide-degrading Firmicutes or Thermotogae-affiliated populations that are historically co-located. HGT material included a saccharolytic operon, from which a CAZyme was biochemically characterized and demonstrated hydrolysis of multiple hemicellulose polysaccharides. Finally, temporal genome-resolved metatranscriptomic analysis of SEM1b revealed expression of C. proteolyticus CAZymes at different SEM1b life stages as well as co-expression of CAZymes from multiple SEM1b populations, inferring deeper microbial interactions that are dedicated toward community degradation of cellulose and hemicellulose. We show that C. proteolyticus, a ubiquitous population, consists of closely related strains that have adapted via HGT to presumably degrade both oligo- and longer polysaccharides present in decaying plants and microbial cell walls, thus explaining its dominance in thermophilic anaerobic digesters on a global scale.
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Affiliation(s)
- Benoit J Kunath
- Faculty of Chemistry, Biotechnology and Food Science, Norwegian University of Life Sciences, Ås, 1432, Norway
| | - Francesco Delogu
- Faculty of Chemistry, Biotechnology and Food Science, Norwegian University of Life Sciences, Ås, 1432, Norway
| | - Adrian E Naas
- Faculty of Chemistry, Biotechnology and Food Science, Norwegian University of Life Sciences, Ås, 1432, Norway
| | - Magnus Ø Arntzen
- Faculty of Chemistry, Biotechnology and Food Science, Norwegian University of Life Sciences, Ås, 1432, Norway
| | - Vincent G H Eijsink
- Faculty of Chemistry, Biotechnology and Food Science, Norwegian University of Life Sciences, Ås, 1432, Norway
| | - Bernard Henrissat
- Architecture et Fonction des Macromolécules Biologiques, CNRS, Aix-Marseille Université, Marseille, F-13288, France
| | - Torgeir R Hvidsten
- Faculty of Chemistry, Biotechnology and Food Science, Norwegian University of Life Sciences, Ås, 1432, Norway
| | - Phillip B Pope
- Faculty of Chemistry, Biotechnology and Food Science, Norwegian University of Life Sciences, Ås, 1432, Norway.
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9
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Froese A, Schellenberg J, Sparling R. Enhanced depolymerization and utilization of raw lignocellulosic material by co-cultures of Ruminiclostridium thermocellum with hemicellulose-utilizing partners. Can J Microbiol 2019; 65:296-307. [PMID: 30608879 DOI: 10.1139/cjm-2018-0535] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Ruminiclostridium thermocellum is one of the most promising candidates for consolidated bioprocessing (CBP) of low-cost lignocellulosic materials to biofuels but it still shows poor performance in its ability to deconstruct untreated lignocellulosic substrates. One promising approach to increase R. thermocellum's rate of hydrolysis is to co-culture this cellulose-specialist with partners that possess synergistic hydrolysis enzymes and metabolic capabilities. We have created co-cultures of R. thermocellum with two hemicellulose utilizers, Ruminiclostridium stercorarium and Thermoanaerobacter thermohydrosulfuricus, both of which secrete xylanolytic enzymes and utilize the pentose oligo- and monosaccharides that inhibit R. thermocellum's hydrolysis and metabolism. When grown on milled wheat straw, the co-cultures were able to solubilize up to 58% more of the total polysaccharides than the R. thermocellum mono-culture control. Repeated passaging of the co-cultures on wheat straw yielded stable populations with reduced R. thermocellum cell numbers, indicating competition for cellodextrins released from cellulose hydrolysis, although these stabilized co-cultures were still able to outperform the mono-culture controls. Repeated passaging on Avicel cellulose also yielded stable populations. Overall, the observed synergism suggests that co-culturing R. thermocellum with other members is a viable option for increasing the rate and extent of untreated lignocellulose deconstruction by R. thermocellum for CBP purposes.
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Affiliation(s)
- Alan Froese
- Department of Microbiology, University of Manitoba, Winnipeg, MB R3T 2N2, Canada.,Department of Microbiology, University of Manitoba, Winnipeg, MB R3T 2N2, Canada
| | - John Schellenberg
- Department of Microbiology, University of Manitoba, Winnipeg, MB R3T 2N2, Canada.,Department of Microbiology, University of Manitoba, Winnipeg, MB R3T 2N2, Canada
| | - Richard Sparling
- Department of Microbiology, University of Manitoba, Winnipeg, MB R3T 2N2, Canada
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10
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Structural enzymology reveals the molecular basis of substrate regiospecificity and processivity of an exemplar bacterial glycoside hydrolase family 74 endo-xyloglucanase. Biochem J 2018; 475:3963-3978. [PMID: 30463871 DOI: 10.1042/bcj20180763] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2018] [Revised: 11/18/2018] [Accepted: 11/21/2018] [Indexed: 12/21/2022]
Abstract
Paenibacillus odorifer produces a single multimodular enzyme containing a glycoside hydrolase (GH) family 74 module (AIQ73809). Recombinant production and characterization of the GH74 module (PoGH74cat) revealed a highly specific, processive endo-xyloglucanase that can hydrolyze the polysaccharide backbone at both branched and unbranched positions. X-ray crystal structures obtained for the free enzyme and oligosaccharide complexes evidenced an extensive hydrophobic binding platform - the first in GH74 extending from subsites -4 to +6 - and unique mobile active-site loops. Site-directed mutagenesis revealed that glycine-476 was uniquely responsible for the promiscuous backbone-cleaving activity of PoGH74cat; replacement with tyrosine, which is conserved in many GH74 members, resulted in exclusive hydrolysis at unbranched glucose units. Likewise, systematic replacement of the hydrophobic platform residues constituting the positive subsites indicated their relative contributions to the processive mode of action. Specifically, W347 (+3 subsite) and W348 (+5 subsite) are essential for processivity, while W406 (+2 subsite) and Y372 (+6 subsite) are not strictly essential, but aid processivity.
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11
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Leis B, Held C, Andreeßen B, Liebl W, Graubner S, Schulte LP, Schwarz WH, Zverlov VV. Optimizing the composition of a synthetic cellulosome complex for the hydrolysis of softwood pulp: identification of the enzymatic core functions and biochemical complex characterization. BIOTECHNOLOGY FOR BIOFUELS 2018; 11:220. [PMID: 30116297 PMCID: PMC6083626 DOI: 10.1186/s13068-018-1220-y] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/07/2018] [Accepted: 07/31/2018] [Indexed: 05/30/2023]
Abstract
BACKGROUND The development of efficient cellulase blends is a key factor for cost-effectively valorizing biomass in a new bio-economy. Today, the enzymatic hydrolysis of plant-derived polysaccharides is mainly accomplished with fungal cellulases, whereas potentially equally effective cellulose-degrading systems from bacteria have not been developed. Particularly, a thermostable multi-enzyme cellulase complex, the cellulosome from the anaerobic cellulolytic bacterium Clostridium thermocellum is promising of being applied as cellulolytic nano-machinery for the production of fermentable sugars from cellulosic biomass. RESULTS In this study, 60 cellulosomal components were recombinantly produced in E. coli and systematically permuted in synthetic complexes to study the function-activity relationship of all available enzymes on Kraft pulp from pine wood as the substrate. Starting from a basic exo/endoglucanase complex, we were able to identify additional functional classes such as mannanase and xylanase for optimal activity on the substrate. Based on these results, we predicted a synthetic cellulosome complex consisting of seven single components (including the scaffoldin protein and a β-glucosidase) and characterized it biochemically. We obtained a highly thermostable complex with optimal activity around 60-65 °C and an optimal pH in agreement with the optimum of the native cellulosome (pH 5.8). Remarkably, a fully synthetic complex containing 47 single cellulosomal components showed comparable activity with a commercially available fungal enzyme cocktail on the softwood pulp substrate. CONCLUSIONS Our results show that synthetic bacterial multi-enzyme complexes based on the cellulosome of C. thermocellum can be applied as a versatile platform for the quick adaptation and efficient degradation of a substrate of interest.
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Affiliation(s)
- Benedikt Leis
- Department of Microbiology, Technische Universität München, TUM School of Life Sciences Weihenstephan, Emil-Ramann-Str. 4, 85354 Freising, Germany
- Present Address: Fraunhofer Institute for Molecular Biology and Applied Ecology IME, Winchester Str. 2, 35394 Gießen, Germany
| | - Claudia Held
- Department of Microbiology, Technische Universität München, TUM School of Life Sciences Weihenstephan, Emil-Ramann-Str. 4, 85354 Freising, Germany
| | - Björn Andreeßen
- Department of Microbiology, Technische Universität München, TUM School of Life Sciences Weihenstephan, Emil-Ramann-Str. 4, 85354 Freising, Germany
| | - Wolfgang Liebl
- Department of Microbiology, Technische Universität München, TUM School of Life Sciences Weihenstephan, Emil-Ramann-Str. 4, 85354 Freising, Germany
| | - Sigrid Graubner
- Department of Microbiology, Technische Universität München, TUM School of Life Sciences Weihenstephan, Emil-Ramann-Str. 4, 85354 Freising, Germany
| | - Louis-Philipp Schulte
- Department of Microbiology, Technische Universität München, TUM School of Life Sciences Weihenstephan, Emil-Ramann-Str. 4, 85354 Freising, Germany
| | - Wolfgang H. Schwarz
- Department of Microbiology, Technische Universität München, TUM School of Life Sciences Weihenstephan, Emil-Ramann-Str. 4, 85354 Freising, Germany
| | - Vladimir V. Zverlov
- Department of Microbiology, Technische Universität München, TUM School of Life Sciences Weihenstephan, Emil-Ramann-Str. 4, 85354 Freising, Germany
- Institute of Molecular Genetics, Russian Academy of Science, Kurchatov Sq. 2, Moscow, 123182 Russia
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Affiliation(s)
- R. Rashmi
- Institute of Bioinformatics and Applied Biotechnology, Bengaluru, India
| | - K. R. Siddalingamurthy
- Department of Biochemistry, Jnanabharathi Campus, Bangalore University, Bengaluru, India
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Identification of endoxylanase XynE from Clostridium thermocellum as the first xylanase of glycoside hydrolase family GH141. Sci Rep 2017; 7:11178. [PMID: 28894250 PMCID: PMC5593877 DOI: 10.1038/s41598-017-11598-y] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2017] [Accepted: 08/24/2017] [Indexed: 11/10/2022] Open
Abstract
Enzymes that cleave polysaccharides in lignocellulose, i. e., cellulases, xylanases, and accessory enzymes, play crucial roles in the natural decomposition of plant-derived biomass and its efficient and sustainable processing into biofuels or other bulk chemicals. The analysis of open reading frame cthe_2195 from the thermophilic, cellulolytic anaerobe Clostridium thermocellum (also known as ‘Ruminiclostridium thermocellum’) suggested that it encoded a cellulosomal protein comprising a dockerin-I module, a carbohydrate-binding module, and a module of previously unknown function. The biochemical characterisation upon recombinant expression in Escherichia coli revealed that the protein is a thermostable endoxylanase, named Xyn141E with an optimal pH of 6.0–6.5 and a temperature optimum of 67–75 °C. The substrate spectrum of Xyn141E resembles that of GH10 xylanases, because of its side activities on carboxymethyl cellulose, barley β-glucan, and mannan. Conversely, the product spectrum of Xyn141E acting on arabinoxylan is similar to those of GH11, as established by HPAEC-PAD analysis. Xyn141E is weakly related (20.7% amino acid sequence identity) to the founding member of the recently established GH family 141 and is the first xylanase in this new family of biomass-degrading enzymes.
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Mechelke M, Koeck DE, Broeker J, Roessler B, Krabichler F, Schwarz WH, Zverlov VV, Liebl W. Characterization of the arabinoxylan-degrading machinery of the thermophilic bacterium Herbinix hemicellulosilytica-Six new xylanases, three arabinofuranosidases and one xylosidase. J Biotechnol 2017; 257:122-130. [PMID: 28450260 DOI: 10.1016/j.jbiotec.2017.04.023] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2016] [Revised: 04/20/2017] [Accepted: 04/20/2017] [Indexed: 10/19/2022]
Abstract
Herbinix hemicellulosilytica is a newly isolated, gram-positive, anaerobic bacterium with extensive hemicellulose-degrading capabilities obtained from a thermophilic biogas reactor. In order to exploit its potential as a source for new industrial arabinoxylan-degrading enzymes, six new thermophilic xylanases, four from glycoside hydrolase family 10 (GH10) and two from GH11, three arabinofuranosidases (1x GH43, 2x GH51) and one β-xylosidase (GH43) were selected. The recombinantly produced enzymes were purified and characterized. All enzymes were active on different xylan-based polysaccharides and most of them showed temperature-vs-activity profiles with maxima around 55-65°C. HPAEC-PAD analysis of the hydrolysates of wheat arabinoxylan and of various purified xylooligosaccharides (XOS) and arabinoxylooligosaccharides (AXOS) was used to investigate their substrate and product specificities: among the GH10 xylanases, XynB showed a different product pattern when hydrolysing AXOS compared to XynA, XynC, and XynD. None of the GH11 xylanases was able to degrade any of the tested AXOS. All three arabinofuranosidases, ArfA, ArfB and ArfC, were classified as type AXH-m,d enzymes. None of the arabinofuranosidases was able to degrade the double-arabinosylated xylooligosaccharides XA2+3XX. β-Xylosidase XylA (GH43) was able to degrade unsubstituted XOS, but showed limited activity to degrade AXOS.
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Affiliation(s)
- M Mechelke
- Department of Microbiology, Technical University of Munich, Emil-Ramann-Str. 4, 85354 Freising-Weihenstephan, Germany
| | - D E Koeck
- Department of Microbiology, Technical University of Munich, Emil-Ramann-Str. 4, 85354 Freising-Weihenstephan, Germany
| | - J Broeker
- Department of Microbiology, Technical University of Munich, Emil-Ramann-Str. 4, 85354 Freising-Weihenstephan, Germany
| | - B Roessler
- Department of Microbiology, Technical University of Munich, Emil-Ramann-Str. 4, 85354 Freising-Weihenstephan, Germany
| | - F Krabichler
- Department of Microbiology, Technical University of Munich, Emil-Ramann-Str. 4, 85354 Freising-Weihenstephan, Germany
| | - W H Schwarz
- Department of Microbiology, Technical University of Munich, Emil-Ramann-Str. 4, 85354 Freising-Weihenstephan, Germany
| | - V V Zverlov
- Department of Microbiology, Technical University of Munich, Emil-Ramann-Str. 4, 85354 Freising-Weihenstephan, Germany; Institute of Molecular Genetics, Russian Academy of Science, Kurchatov Sq. 2, 123182 Moscow Russia
| | - W Liebl
- Department of Microbiology, Technical University of Munich, Emil-Ramann-Str. 4, 85354 Freising-Weihenstephan, Germany.
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Enzymatic diversity of the Clostridium thermocellum cellulosome is crucial for the degradation of crystalline cellulose and plant biomass. Sci Rep 2016; 6:35709. [PMID: 27759119 PMCID: PMC5069625 DOI: 10.1038/srep35709] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2016] [Accepted: 10/03/2016] [Indexed: 01/18/2023] Open
Abstract
The cellulosome is a supramolecular multienzyme complex comprised of a wide variety of polysaccharide-degrading enzymes and scaffold proteins. The cellulosomal enzymes that bind to the scaffold proteins synergistically degrade crystalline cellulose. Here, we report in vitro reconstitution of the Clostridium thermocellum cellulosome from 40 cellulosomal components and the full-length scaffoldin protein that binds to nine enzyme molecules. These components were each synthesized using a wheat germ cell-free protein synthesis system and purified. Cellulosome complexes were reconstituted from 3, 12, 30, and 40 components based on their contents in the native cellulosome. The activity of the enzyme-saturated complex indicated that greater enzymatic variety generated more synergy for the degradation of crystalline cellulose and delignified rice straw. Surprisingly, a less complete enzyme complex displaying fewer than nine enzyme molecules was more efficient for the degradation of delignified rice straw than the enzyme-saturated complex, despite the fact that the enzyme-saturated complex exhibited maximum synergy for the degradation of crystalline cellulose. These results suggest that greater enzymatic diversity of the cellulosome is crucial for the degradation of crystalline cellulose and plant biomass, and that efficient degradation of different substrates by the cellulosome requires not only a different enzymatic composition, but also different cellulosome structures.
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Attia M, Stepper J, Davies GJ, Brumer H. Functional and structural characterization of a potent GH74 endo-xyloglucanase from the soil saprophyte Cellvibrio japonicus unravels the first step of xyloglucan degradation. FEBS J 2016; 283:1701-19. [PMID: 26929175 DOI: 10.1111/febs.13696] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2015] [Revised: 02/09/2016] [Accepted: 02/25/2016] [Indexed: 11/27/2022]
Abstract
UNLABELLED The heteropolysaccharide xyloglucan (XyG) comprises up to one-quarter of the total carbohydrate content of terrestrial plant cell walls and, as such, represents a significant reservoir in the global carbon cycle. The complex composition of XyG requires a consortium of backbone-cleaving endo-xyloglucanases and side-chain cleaving exo-glycosidases for complete saccharification. The biochemical basis for XyG utilization by the model Gram-negative soil saprophytic bacterium Cellvibrio japonicus is incompletely understood, despite the recent characterization of associated side-chain cleaving exo-glycosidases. We present a detailed functional and structural characterization of a multimodular enzyme encoded by gene locus CJA_2477. The CJA_2477 gene product comprises an N-terminal glycoside hydrolase family 74 (GH74) endo-xyloglucanase module in train with two carbohydrate-binding modules (CBMs) from families 10 and 2 (CBM10 and CBM2). The GH74 catalytic domain generates Glc4 -based xylogluco-oligosaccharide (XyGO) substrates for downstream enzymes through an endo-dissociative mode of action. X-ray crystallography of the GH74 module, alone and in complex with XyGO products spanning the entire active site, revealed a broad substrate-binding cleft specifically adapted to XyG recognition, which is composed of two seven-bladed propeller domains characteristic of the GH74 family. The appended CBM10 and CBM2 members notably did not bind XyG, nor other soluble polysaccharides, and instead were specific cellulose-binding modules. Taken together, these data shed light on the first step of xyloglucan utilization by C. japonicus and expand the repertoire of GHs and CBMs for selective biomass analysis and utilization. DATABASE Structural data have been deposited in the RCSB protein database under the Protein Data Bank codes: 5FKR, 5FKS, 5FKT and 5FKQ.
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Affiliation(s)
- Mohamed Attia
- Michael Smith Laboratories and Department of Chemistry, University of British Columbia, Vancouver, Canada
| | | | | | - Harry Brumer
- Michael Smith Laboratories and Department of Chemistry, University of British Columbia, Vancouver, Canada
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Mechanisms involved in xyloglucan catabolism by the cellulosome-producing bacterium Ruminiclostridium cellulolyticum. Sci Rep 2016; 6:22770. [PMID: 26946939 PMCID: PMC4780118 DOI: 10.1038/srep22770] [Citation(s) in RCA: 51] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2015] [Accepted: 02/23/2016] [Indexed: 12/23/2022] Open
Abstract
Xyloglucan, a ubiquitous highly branched plant polysaccharide, was found to be rapidly degraded and metabolized by the cellulosome-producing bacterium Ruminiclostridium cellulolyticum. Our study shows that at least four cellulosomal enzymes displaying either endo- or exoxyloglucanase activities, achieve the extracellular degradation of xyloglucan into 4-glucosyl backbone xyloglucan oligosaccharides. The released oligosaccharides (composed of up to 9 monosaccharides) are subsequently imported by a highly specific ATP-binding cassette transporter (ABC-transporter), the expression of the corresponding genes being strongly induced by xyloglucan. This polysaccharide also triggers the synthesis of cytoplasmic β-galactosidase, α-xylosidase, and β-glucosidase that act sequentially to convert the imported oligosaccharides into galactose, xylose, glucose and unexpectedly cellobiose. Thus R. cellulolyticum has developed an energy-saving strategy to metabolize this hemicellulosic polysaccharide that relies on the action of the extracellular cellulosomes, a highly specialized ABC-transporter, and cytoplasmic enzymes acting in a specific order. This strategy appears to be widespread among cellulosome-producing mesophilic bacteria which display highly similar gene clusters encoding the cytosolic enzymes and the ABC-transporter.
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Moraïs S, Ben David Y, Bensoussan L, Duncan SH, Koropatkin NM, Martens EC, Flint HJ, Bayer EA. Enzymatic profiling of cellulosomal enzymes from the human gut bacterium, Ruminococcus champanellensis, reveals a fine-tuned system for cohesin-dockerin recognition. Environ Microbiol 2016; 18:542-56. [PMID: 26347002 DOI: 10.1111/1462-2920.13047] [Citation(s) in RCA: 43] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2015] [Revised: 09/02/2015] [Accepted: 09/02/2015] [Indexed: 12/16/2023]
Abstract
Ruminococcus champanellensis is considered a keystone species in the human gut that degrades microcrystalline cellulose efficiently and contains the genetic elements necessary for cellulosome production. The basic elements of its cellulosome architecture, mainly cohesin and dockerin modules from scaffoldins and enzyme-borne dockerins, have been characterized recently. In this study, we cloned, expressed and characterized all of the glycoside hydrolases that contain a dockerin module. Among the 25 enzymes, 10 cellulases, 4 xylanases, 3 mannanases, 2 xyloglucanases, 2 arabinofuranosidases, 2 arabinanases and one β-glucanase were assessed for their comparative enzymatic activity on their respective substrates. The dockerin specificities of the enzymes were examined by ELISA, and 80 positives out of 525 possible interactions were detected. Our analysis reveals a fine-tuned system for cohesin-dockerin specificity and the importance of diversity among the cohesin-dockerin sequences. Our results imply that cohesin-dockerin pairs are not necessarily assembled at random among the same specificity types, as generally believed for other cellulosome-producing bacteria, but reveal a more organized cellulosome architecture. Moreover, our results highlight the importance of the cellulosome paradigm for cellulose and hemicellulose degradation by R. champanellensis in the human gut.
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Affiliation(s)
- Sarah Moraïs
- Department of Biological Chemistry, The Weizmann Institute of Science, Rehovot, Israel
| | - Yonit Ben David
- Department of Biological Chemistry, The Weizmann Institute of Science, Rehovot, Israel
| | - Lizi Bensoussan
- Department of Biological Chemistry, The Weizmann Institute of Science, Rehovot, Israel
| | - Sylvia H Duncan
- Microbiology Group, Rowett Institute of Nutrition and Health, University of Aberdeen, Aberdeen, UK
| | - Nicole M Koropatkin
- Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor, MI, 48109, USA
| | - Eric C Martens
- Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor, MI, 48109, USA
| | - Harry J Flint
- Microbiology Group, Rowett Institute of Nutrition and Health, University of Aberdeen, Aberdeen, UK
| | - Edward A Bayer
- Department of Biological Chemistry, The Weizmann Institute of Science, Rehovot, Israel
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Decoding Biomass-Sensing Regulons of Clostridium thermocellum Alternative Sigma-I Factors in a Heterologous Bacillus subtilis Host System. PLoS One 2016; 11:e0146316. [PMID: 26731480 PMCID: PMC4711584 DOI: 10.1371/journal.pone.0146316] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2015] [Accepted: 12/15/2015] [Indexed: 11/25/2022] Open
Abstract
The Gram-positive, anaerobic, cellulolytic, thermophile Clostridium (Ruminiclostridium) thermocellum secretes a multi-enzyme system called the cellulosome to solubilize plant cell wall polysaccharides. During the saccharolytic process, the enzymatic composition of the cellulosome is modulated according to the type of polysaccharide(s) present in the environment. C. thermocellum has a set of eight alternative RNA polymerase sigma (σ) factors that are activated in response to extracellular polysaccharides and share sequence similarity to the Bacillus subtilis σI factor. The aim of the present work was to demonstrate whether individual C. thermocellum σI-like factors regulate specific cellulosomal genes, focusing on C. thermocellum σI6 and σI3 factors. To search for putative σI6- and σI3-dependent promoters, bioinformatic analysis of the upstream regions of the cellulosomal genes was performed. Because of the limited genetic tools available for C. thermocellum, the functionality of the predicted σI6- and σI3-dependent promoters was studied in B. subtilis as a heterologous host. This system enabled observation of the activation of 10 predicted σI6-dependent promoters associated with the C. thermocellum genes: sigI6 (itself, Clo1313_2778), xyn11B (Clo1313_0522), xyn10D (Clo1313_0177), xyn10Z (Clo1313_2635), xyn10Y (Clo1313_1305), cel9V (Clo1313_0349), cseP (Clo1313_2188), sigI1 (Clo1313_2174), cipA (Clo1313_0627), and rsgI5 (Clo1313_0985). Additionally, we observed the activation of 4 predicted σI3-dependent promoters associated with the C. thermocellum genes: sigI3 (itself, Clo1313_1911), pl11 (Clo1313_1983), ce12 (Clo1313_0693) and cipA. Our results suggest possible regulons of σI6 and σI3 in C. thermocellum, as well as the σI6 and σI3 promoter consensus sequences. The proposed -35 and -10 promoter consensus elements of σI6 are CNNAAA and CGAA, respectively. Additionally, a less conserved CGA sequence next to the C in the -35 element and a highly conserved AT sequence three bases downstream of the -10 element were also identified as important nucleotides for promoter recognition. Regarding σI3, the proposed -35 and -10 promoter consensus elements are CCCYYAAA and CGWA, respectively. The present study provides new clues for understanding these recently discovered alternative σI factors.
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Affiliation(s)
- Tomohiko Matsuzawa
- Bioproduction Research Institute, National Institute of Advanced Industrial Science and Technology (AIST)
| | - Katsuro Yaoi
- Bioproduction Research Institute, National Institute of Advanced Industrial Science and Technology (AIST)
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21
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Affiliation(s)
- Tomohiko Matsuzawa
- Bioproduction Research Institute, National Institute of Advanced Industrial Science and Technology (AIST)
| | - Katsuro Yaoi
- Bioproduction Research Institute, National Institute of Advanced Industrial Science and Technology (AIST)
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22
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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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23
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Bhattacharya AS, Bhattacharya A, Pletschke BI. Synergism of fungal and bacterial cellulases and hemicellulases: a novel perspective for enhanced bio-ethanol production. Biotechnol Lett 2015; 37:1117-29. [DOI: 10.1007/s10529-015-1779-3] [Citation(s) in RCA: 73] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2015] [Accepted: 01/21/2015] [Indexed: 12/15/2022]
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Akinosho H, Yee K, Close D, Ragauskas A. The emergence of Clostridium thermocellum as a high utility candidate for consolidated bioprocessing applications. Front Chem 2014; 2:66. [PMID: 25207268 PMCID: PMC4143619 DOI: 10.3389/fchem.2014.00066] [Citation(s) in RCA: 105] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2014] [Accepted: 07/28/2014] [Indexed: 01/25/2023] Open
Abstract
First isolated in 1926, Clostridium thermocellum has recently received increased attention as a high utility candidate for use in consolidated bioprocessing (CBP) applications. These applications, which seek to process lignocellulosic biomass directly into useful products such as ethanol, are gaining traction as economically feasible routes toward the production of fuel and other high value chemical compounds as the shortcomings of fossil fuels become evident. This review evaluates C. thermocellum's role in this transitory process by highlighting recent discoveries relating to its genomic, transcriptomic, proteomic, and metabolomic responses to varying biomass sources, with a special emphasis placed on providing an overview of its unique, multivariate enzyme cellulosome complex and the role that this structure performs during biomass degradation. Both naturally evolved and genetically engineered strains are examined in light of their unique attributes and responses to various biomass treatment conditions, and the genetic tools that have been employed for their creation are presented. Several future routes for potential industrial usage are presented, and it is concluded that, although there have been many advances to significantly improve C. thermocellum's amenability to industrial use, several hurdles still remain to be overcome as this unique organism enjoys increased attention within the scientific community.
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Affiliation(s)
- Hannah Akinosho
- School of Chemistry and Biochemistry, Institute of Paper Science and Technology, Georgia Institute of Technology Atlanta, GA, USA ; Oak Ridge National Laboratory, BioEnergy Science Center Oak Ridge, TN, USA
| | - Kelsey Yee
- Oak Ridge National Laboratory, BioEnergy Science Center Oak Ridge, TN, USA ; Biosciences Division, Oak Ridge National Laboratory Oak Ridge, TN, USA
| | - Dan Close
- Biosciences Division, Oak Ridge National Laboratory Oak Ridge, TN, USA
| | - Arthur Ragauskas
- Oak Ridge National Laboratory, BioEnergy Science Center Oak Ridge, TN, USA ; Department of Chemical and Biomolecular Engineering and Department of Forestry, Wildlife, and Fisheries, University of Tennessee Knoxville, TN, USA
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25
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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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Key amino acid residues for the endo-processive activity of GH74 xyloglucanase. FEBS Lett 2014; 588:1731-8. [PMID: 24657616 DOI: 10.1016/j.febslet.2014.03.023] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/25/2013] [Revised: 03/11/2014] [Accepted: 03/11/2014] [Indexed: 11/22/2022]
Abstract
Unlike endo-dissociative-xyloglucanases, Paenibacillus XEG74 is an endo-processive xyloglucanase that contains four unique tryptophan residues in the negative subsites (W61 and W64) and the positive subsites (W318 and W319), as indicated by three-dimensional homology modelling. Selective replacement of the positive subsite residues with alanine mutations reduced the degree of processive activity and resulted in the more endo-dissociative-activity. The results showed that W318 and W319, which are found in the positive subsites, are essential for processive degradation and are responsible for maintaining binding interactions with xyloglucan polysaccharide through a stacking effect.
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Ravachol J, Borne R, Tardif C, de Philip P, Fierobe HP. Characterization of all family-9 glycoside hydrolases synthesized by the cellulosome-producing bacterium Clostridium cellulolyticum. J Biol Chem 2014; 289:7335-48. [PMID: 24451379 DOI: 10.1074/jbc.m113.545046] [Citation(s) in RCA: 61] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
The genome of Clostridium cellulolyticum encodes 13 GH9 enzymes that display seven distinct domain organizations. All but one contain a dockerin module and were formerly detected in the cellulosomes, but only three of them were previously studied (Cel9E, Cel9G, and Cel9M). In this study, the 10 uncharacterized GH9 enzymes were overproduced in Escherichia coli and purified, and their activity pattern was investigated in the free state or in cellulosome chimeras with key cellulosomal cellulases. The newly purified GH9 enzymes, including those that share similar organization, all exhibited distinct activity patterns, various binding capacities on cellulosic substrates, and different synergies with pivotal cellulases in mini-cellulosomes. Furthermore, one enzyme (Cel9X) was characterized as the first genuine endoxyloglucanase belonging to this family, with no activity on soluble and insoluble celluloses. Another GH9 enzyme (Cel9V), whose sequence is 78% identical to the cellulosomal cellulase Cel9E, was found inactive in the free and complexed states on all tested substrates. The sole noncellulosomal GH9 (Cel9W) is a cellulase displaying a broad substrate specificity, whose engineered form bearing a dockerin can act synergistically in minicomplexes. Finally, incorporation of all GH9 cellulases in trivalent cellulosome chimera containing Cel48F and Cel9G generated a mixture of heterogeneous mini-cellulosomes that exhibit more activity on crystalline cellulose than the best homogeneous tri-functional complex. Altogether, our data emphasize the importance of GH9 diversity in bacterial cellulosomes, confirm that Cel9G is the most synergistic GH9 with the major endoprocessive cellulase Cel48F, but also identify Cel9U as an important cellulosomal component during cellulose depolymerization.
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Affiliation(s)
- Julie Ravachol
- From the Aix-Marseille Université-CNRS, Laboratoire de Chimie Bactérienne UMR7283, Institut de Microbiologie de la Méditerranée, Marseille Cedex 20, France
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Hirano N, Hasegawa H, Nihei S, Haruki M. Cell-free protein synthesis and substrate specificity of full-length endoglucanase CelJ (Cel9D-Cel44A), the largest multi-enzyme subunit of theClostridium thermocellumcellulosome. FEMS Microbiol Lett 2013; 344:25-30. [DOI: 10.1111/1574-6968.12149] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2013] [Revised: 04/01/2013] [Accepted: 04/01/2013] [Indexed: 11/28/2022] Open
Affiliation(s)
| | - Hiroki Hasegawa
- Department of Chemical Biology & Applied Chemistry; College of Engineering; Nihon University; Koriyama; Fukushima; Japan
| | - Satoshi Nihei
- Department of Chemical Biology & Applied Chemistry; College of Engineering; Nihon University; Koriyama; Fukushima; Japan
| | - Mitsuru Haruki
- Department of Chemical Biology & Applied Chemistry; College of Engineering; Nihon University; Koriyama; Fukushima; Japan
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Verbeke TJ, Zhang X, Henrissat B, Spicer V, Rydzak T, Krokhin OV, Fristensky B, Levin DB, Sparling R. Genomic evaluation of Thermoanaerobacter spp. for the construction of designer co-cultures to improve lignocellulosic biofuel production. PLoS One 2013; 8:e59362. [PMID: 23555660 PMCID: PMC3608648 DOI: 10.1371/journal.pone.0059362] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2012] [Accepted: 02/13/2013] [Indexed: 02/07/2023] Open
Abstract
The microbial production of ethanol from lignocellulosic biomass is a multi-component process that involves biomass hydrolysis, carbohydrate transport and utilization, and finally, the production of ethanol. Strains of the genus Thermoanaerobacter have been studied for decades due to their innate abilities to produce comparatively high ethanol yields from hemicellulose constituent sugars. However, their inability to hydrolyze cellulose, limits their usefulness in lignocellulosic biofuel production. As such, co-culturing Thermoanaerobacter spp. with cellulolytic organisms is a plausible approach to improving lignocellulose conversion efficiencies and yields of biofuels. To evaluate native lignocellulosic ethanol production capacities relative to competing fermentative end-products, comparative genomic analysis of 11 sequenced Thermoanaerobacter strains, including a de novo genome, Thermoanaerobacter thermohydrosulfuricus WC1, was conducted. Analysis was specifically focused on the genomic potential for each strain to address all aspects of ethanol production mentioned through a consolidated bioprocessing approach. Whole genome functional annotation analysis identified three distinct clades within the genus. The genomes of Clade 1 strains encode the fewest extracellular carbohydrate active enzymes and also show the least diversity in terms of lignocellulose relevant carbohydrate utilization pathways. However, these same strains reportedly are capable of directing a higher proportion of their total carbon flux towards ethanol, rather than non-biofuel end-products, than other Thermoanaerobacter strains. Strains in Clade 2 show the greatest diversity in terms of lignocellulose hydrolysis and utilization, but proportionately produce more non-ethanol end-products than Clade 1 strains. Strains in Clade 3, in which T. thermohydrosulfuricus WC1 is included, show mid-range potential for lignocellulose hydrolysis and utilization, but also exhibit extensive divergence from both Clade 1 and Clade 2 strains in terms of cellular energetics. The potential implications regarding strain selection and suitability for industrial ethanol production through a consolidated bioprocessing co-culturing approach are examined throughout the manuscript.
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Affiliation(s)
- Tobin J. Verbeke
- Department of Microbiology, University of Manitoba, Winnipeg, Manitoba, Canada
| | - Xiangli Zhang
- Department of Plant Science, University of Manitoba, Winnipeg, Manitoba, Canada
| | - Bernard Henrissat
- Centre national de la recherche scientifique, Aix-Marseille Université, Marseille, France
| | - Vic Spicer
- Department of Physics & Astronomy, University of Manitoba, Winnipeg, Manitoba, Canada
| | - Thomas Rydzak
- Department of Microbiology, University of Manitoba, Winnipeg, Manitoba, Canada
| | - Oleg V. Krokhin
- Department of Internal Medicine & Manitoba Centre for Proteomics and Systems Biology, University of Manitoba, Winnipeg, Manitoba, Canada
| | - Brian Fristensky
- Department of Plant Science, University of Manitoba, Winnipeg, Manitoba, Canada
| | - David B. Levin
- Biosystems Engineering, University of Manitoba, Winnipeg, Manitoba, Canada
| | - Richard Sparling
- Department of Microbiology, University of Manitoba, Winnipeg, Manitoba, Canada
- * E-mail:
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Bhalla A, Bansal N, Kumar S, Bischoff KM, Sani RK. Improved lignocellulose conversion to biofuels with thermophilic bacteria and thermostable enzymes. BIORESOURCE TECHNOLOGY 2013; 128:751-9. [PMID: 23246299 DOI: 10.1016/j.biortech.2012.10.145] [Citation(s) in RCA: 174] [Impact Index Per Article: 15.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/01/2012] [Revised: 09/20/2012] [Accepted: 10/29/2012] [Indexed: 05/07/2023]
Abstract
Second-generation feedstock, especially nonfood lignocellulosic biomass is a potential source for biofuel production. Cost-intensive physical, chemical, biological pretreatment operations and slow enzymatic hydrolysis make the overall process of lignocellulosic conversion into biofuels less economical than available fossil fuels. Lignocellulose conversions carried out at ≤ 50 °C have several limitations. Therefore, this review focuses on the importance of thermophilic bacteria and thermostable enzymes to overcome the limitations of existing lignocellulosic biomass conversion processes. The influence of high temperatures on various existing lignocellulose conversion processes and those that are under development, including separate hydrolysis and fermentation, simultaneous saccharification and fermentation, and extremophilic consolidated bioprocess are also discussed.
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Affiliation(s)
- Aditya Bhalla
- Department of Chemical and Biological Engineering, South Dakota School of Mines and Technology, Rapid City, SD 57701, USA
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Characterization of an endo-processive-type xyloglucanase having a β-1,4-glucan-binding module and an endo-type xyloglucanase from Streptomyces avermitilis. Appl Environ Microbiol 2012; 78:7939-45. [PMID: 22941084 DOI: 10.1128/aem.01762-12] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
We cloned two glycoside hydrolase family 74 genes, the sav_1856 gene and the sav_2574 gene, from Streptomyces avermitilis NBRC14893 and characterized the resultant recombinant proteins. The sav_1856 gene product (SaGH74A) consisted of a catalytic domain and a family 2 carbohydrate-binding module at the C terminus, while the sav_2574 gene product (SaGH74B) consisted of only a catalytic domain. SaGH74A and SaGH74B were expressed successfully and had molecular masses of 92 and 78 kDa, respectively. Both recombinant proteins were xyloglucanases. SaGH74A had optimal activity at 60°C and pH 5.5, while SaGH74B had optimal activity at 55°C and pH 6.0. SaGH74A was stable over a broad pH range (pH 4.5 to 9.0), whereas SaGH74B was stable over a relatively narrow pH range (pH 6.0 to 6.5). Analysis of the hydrolysis products of tamarind xyloglucan and xyloglucan-derived oligosaccharides indicated that SaGH74A was endo-processive, while SaGH74B was a typical endo-enzyme. The C terminus of SaGH74A, which was annotated as a carbohydrate-binding module, bound to β-1,4-linked glucan-containing soluble polysaccharides such as hydroxyethyl cellulose, barley glucan, and xyloglucan.
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Comparison of two methods for assaying reducing sugars in the determination of carbohydrase activities. Int J Anal Chem 2011; 2011:283658. [PMID: 21647284 PMCID: PMC3103847 DOI: 10.1155/2011/283658] [Citation(s) in RCA: 128] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2011] [Accepted: 04/06/2011] [Indexed: 11/17/2022] Open
Abstract
The Nelson-Somogyi (NS) and 3,5-dinitrosalicylic acid (DNS) assays for reducing sugars are widely used in measurements of carbohydrase activities against different polysaccharides. Using twelve commercial enzyme preparations, the comparison of the NS and DNS assays in determination of cellulase, β-glucanase, xylanase, and β-mannanase activities was carried out. When cellulase activities against CMC were measured, the DNS assay gave activity values, which were typically 40-50% higher than those obtained with the NS assay. In the analysis of the xylanase, β-mannanase, and β-glucanase activities, the overestimations by the DNS assay were much more pronounced (the observed differences in the activities were 3- to 13-fold). Reasons for preferential use of the NS assay for measuring activities of carbohydrases other than cellulases are discussed.
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33
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Selvaraj T, Kim SK, Kim YH, Jeong YS, Kim YJ, Phuong ND, Jung KH, Kim J, Yun HD, Kim H. The role of carbohydrate-binding module (CBM) repeat of a multimodular xylanase (XynX) from Clostridium thermocellum in cellulose and xylan binding. J Microbiol 2011; 48:856-61. [DOI: 10.1007/s12275-010-0285-5] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2010] [Accepted: 09/15/2010] [Indexed: 10/18/2022]
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Yeoman CJ, Han Y, Dodd D, Schroeder CM, Mackie RI, Cann IKO. Thermostable enzymes as biocatalysts in the biofuel industry. ADVANCES IN APPLIED MICROBIOLOGY 2010; 70:1-55. [PMID: 20359453 DOI: 10.1016/s0065-2164(10)70001-0] [Citation(s) in RCA: 173] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Abstract
Lignocellulose is the most abundant carbohydrate source in nature and represents an ideal renewable energy source. Thermostable enzymes that hydrolyze lignocellulose to its component sugars have significant advantages for improving the conversion rate of biomass over their mesophilic counterparts. We review here the recent literature on the development and use of thermostable enzymes for the depolymerization of lignocellulosic feedstocks for biofuel production. Furthermore, we discuss the protein structure, mechanisms of thermostability, and specific strategies that can be used to improve the thermal stability of lignocellulosic biocatalysts.
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Affiliation(s)
- Carl J Yeoman
- Institute for Genomic Biology, University of Illinois, Urbana, Illinois, USA
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Yaoi K, Kondo H, Hiyoshi A, Noro N, Sugimoto H, Tsuda S, Miyazaki K. The crystal structure of a xyloglucan-specific endo-beta-1,4-glucanase from Geotrichum sp. M128 xyloglucanase reveals a key amino acid residue for substrate specificity. FEBS J 2009; 276:5094-100. [PMID: 19682300 DOI: 10.1111/j.1742-4658.2009.07205.x] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Geotrichum sp. M128 possesses two xyloglucan-specific glycoside hydrolases belonging to family 74, xyloglucan-specific endo-beta-1,4-glucanase (XEG) and oligoxyloglucan reducing-end-specific cellobiohydrolase (OXG-RCBH). Despite their similar amino acid sequences (48% identity), their modes of action and substrate specificities are distinct. XEG catalyzes the hydrolysis of xyloglucan polysaccharides in endo mode, while OXG-RCBH acts on xyloglucan oligosaccharides at the reducing end in exo mode. Here, we determined the crystal structure of XEG at 2.5 A resolution, and compared it to a previously determined structure of OXG-RCBH. For the most part, the amino acid residues that interact with substrate are conserved between the two enzymes. However, there are notable differences at subsite positions -1 and +2. OXG-RCBH has a loop around the +2 site that blocks one end of the active site cleft, which accounts for its exo mode of action. In contrast, XEG lacks a corresponding loop at this site, thereby allowing binding to the middle of the main chain of the substrate. At the -1 site in OXG-RCBH, Asn488 interacts with the xylose side chain of the substrate, whereas the -1 site is occupied by Tyr457 in XEG. To confirm the contribution of this residue to substrate specificity, Tyr457 was substituted by Gly in XEG. The wild-type XEG cleaved the oligoxyloglucan at a specific site; the Y457G variant cleaved the same substrate, but at various sites. Together, the absence of a loop in the cleft and the presence of bulky Tyr457 determine the substrate specificity of XEG.
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Affiliation(s)
- Katsuro Yaoi
- Institute for Biological Resources and Functions, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Ibaraki, Japan.
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Raman B, Pan C, Hurst GB, Rodriguez M, McKeown CK, Lankford PK, Samatova NF, Mielenz JR. Impact of pretreated Switchgrass and biomass carbohydrates on Clostridium thermocellum ATCC 27405 cellulosome composition: a quantitative proteomic analysis. PLoS One 2009; 4:e5271. [PMID: 19384422 PMCID: PMC2668762 DOI: 10.1371/journal.pone.0005271] [Citation(s) in RCA: 167] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2008] [Accepted: 02/12/2009] [Indexed: 11/30/2022] Open
Abstract
Background Economic feasibility and sustainability of lignocellulosic ethanol production requires the development of robust microorganisms that can efficiently degrade and convert plant biomass to ethanol. The anaerobic thermophilic bacterium Clostridium thermocellum is a candidate microorganism as it is capable of hydrolyzing cellulose and fermenting the hydrolysis products to ethanol and other metabolites. C. thermocellum achieves efficient cellulose hydrolysis using multiprotein extracellular enzymatic complexes, termed cellulosomes. Methodology/Principal Findings In this study, we used quantitative proteomics (multidimensional LC-MS/MS and 15N-metabolic labeling) to measure relative changes in levels of cellulosomal subunit proteins (per CipA scaffoldin basis) when C. thermocellum ATCC 27405 was grown on a variety of carbon sources [dilute-acid pretreated switchgrass, cellobiose, amorphous cellulose, crystalline cellulose (Avicel) and combinations of crystalline cellulose with pectin or xylan or both]. Cellulosome samples isolated from cultures grown on these carbon sources were compared to 15N labeled cellulosome samples isolated from crystalline cellulose-grown cultures. In total from all samples, proteomic analysis identified 59 dockerin- and 8 cohesin-module containing components, including 16 previously undetected cellulosomal subunits. Many cellulosomal components showed differential protein abundance in the presence of non-cellulose substrates in the growth medium. Cellulosome samples from amorphous cellulose, cellobiose and pretreated switchgrass-grown cultures displayed the most distinct differences in composition as compared to cellulosome samples from crystalline cellulose-grown cultures. While Glycoside Hydrolase Family 9 enzymes showed increased levels in the presence of crystalline cellulose, and pretreated switchgrass, in particular, GH5 enzymes showed increased levels in response to the presence of cellulose in general, amorphous or crystalline. Conclusions/Significance Overall, the quantitative results suggest a coordinated substrate-specific regulation of cellulosomal subunit composition in C. thermocellum to better suit the organism's needs for growth under different conditions. To date, this study provides the most comprehensive comparison of cellulosomal compositional changes in C. thermocellum in response to different carbon sources. Such studies are vital to engineering a strain that is best suited to grow on specific substrates of interest and provide the building blocks for constructing designer cellulosomes with tailored enzyme composition for industrial ethanol production.
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Affiliation(s)
- Babu Raman
- Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee, United States of America
- BioEnergy Science Center (BESC), Oak Ridge National Laboratory, Oak Ridge, Tennessee, United States of America
| | - Chongle Pan
- Computer Science and Mathematics Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee, United States of America
- BioEnergy Science Center (BESC), Oak Ridge National Laboratory, Oak Ridge, Tennessee, United States of America
| | - Gregory B. Hurst
- Chemical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee, United States of America
- BioEnergy Science Center (BESC), Oak Ridge National Laboratory, Oak Ridge, Tennessee, United States of America
| | - Miguel Rodriguez
- Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee, United States of America
- BioEnergy Science Center (BESC), Oak Ridge National Laboratory, Oak Ridge, Tennessee, United States of America
| | - Catherine K. McKeown
- Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee, United States of America
| | - Patricia K. Lankford
- Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee, United States of America
| | - Nagiza F. Samatova
- Computer Science and Mathematics Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee, United States of America
- Department of Computer Science, North Carolina State University, Raleigh, North Carolina, United States of America
| | - Jonathan R. Mielenz
- Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee, United States of America
- BioEnergy Science Center (BESC), Oak Ridge National Laboratory, Oak Ridge, Tennessee, United States of America
- * E-mail:
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37
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Biosolutions to the energy problem. J Ind Microbiol Biotechnol 2009; 36:319-32. [DOI: 10.1007/s10295-008-0521-8] [Citation(s) in RCA: 113] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2008] [Accepted: 12/16/2008] [Indexed: 10/21/2022]
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Blouzard JC, Bourgeois C, de Philip P, Valette O, Bélaïch A, Tardif C, Bélaïch JP, Pagès S. Enzyme diversity of the cellulolytic system produced by Clostridium cellulolyticum explored by two-dimensional analysis: identification of seven genes encoding new dockerin-containing proteins. J Bacteriol 2007; 189:2300-9. [PMID: 17209020 PMCID: PMC1899368 DOI: 10.1128/jb.00917-06] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The enzyme diversity of the cellulolytic system produced by Clostridium cellulolyticum grown on crystalline cellulose as a sole carbon and energy source was explored by two-dimensional electrophoresis. The cellulolytic system of C. cellulolyticum is composed of at least 30 dockerin-containing proteins (designated cellulosomal proteins) and 30 noncellulosomal components. Most of the known cellulosomal proteins, including CipC, Cel48F, Cel8C, Cel9G, Cel9E, Man5K, Cel9M, and Cel5A, were identified by using two-dimensional Western blot analysis with specific antibodies, whereas Cel5N, Cel9J, and Cel44O were identified by using N-terminal sequencing. Unknown enzymes having carboxymethyl cellulase or xylanase activities were detected by zymogram analysis of two-dimensional gels. Some of these enzymes were identified by N-terminal sequencing as homologs of proteins listed in the NCBI database. Using Trap-Dock PCR and DNA walking, seven genes encoding new dockerin-containing proteins were cloned and sequenced. Some of these genes are clustered. Enzymes encoded by these genes belong to glycoside hydrolase families GH2, GH9, GH10, GH26, GH27, and GH59. Except for members of family GH9, which contains only cellulases, the new modular glycoside hydrolases discovered in this work could be involved in the degradation of different hemicellulosic substrates, such as xylan or galactomannan.
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Affiliation(s)
- Jean-Charles Blouzard
- Laboratoire de Bioénergétique et Ingénierie des Protéines, IBSM, Centre National de la Recherche Scientifique and Université de Provence, Marseille, France
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Martinez-Fleites C, Guerreiro CIPD, Baumann MJ, Taylor EJ, Prates JAM, Ferreira LMA, Fontes CMGA, Brumer H, Davies GJ. Crystal structures of Clostridium thermocellum xyloglucanase, XGH74A, reveal the structural basis for xyloglucan recognition and degradation. J Biol Chem 2006; 281:24922-33. [PMID: 16772298 DOI: 10.1074/jbc.m603583200] [Citation(s) in RCA: 76] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The enzymatic degradation of the plant cell wall is central both to the natural carbon cycle and, increasingly, to environmentally friendly routes to biomass conversion, including the production of biofuels. The plant cell wall is a complex composite of cellulose microfibrils embedded in diverse polysaccharides collectively termed hemicelluloses. Xyloglucan is one such polysaccharide whose hydrolysis is catalyzed by diverse xyloglucanases. Here we present the structure of the Clostridium thermocellum xyloglucanase Xgh74A in both apo and ligand-complexed forms. The structures, in combination with mutagenesis data on the catalytic residues and the kinetics and specificity of xyloglucan hydrolysis reveal a complex subsite specificity accommodating seventeen monosaccharide moieties of the multibranched substrate in an open substrate binding terrain.
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Affiliation(s)
- Carlos Martinez-Fleites
- York Structural Biology Laboratory, Department of Chemitry, University of York, York YO10 5YW, United Kingdom
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