101
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Zoglowek M, Lübeck PS, Ahring BK, Lübeck M. Heterologous expression of cellobiohydrolases in filamentous fungi – An update on the current challenges, achievements and perspectives. Process Biochem 2015. [DOI: 10.1016/j.procbio.2014.12.018] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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102
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Payne CM, Knott BC, Mayes HB, Hansson H, Himmel ME, Sandgren M, Ståhlberg J, Beckham GT. Fungal Cellulases. Chem Rev 2015; 115:1308-448. [DOI: 10.1021/cr500351c] [Citation(s) in RCA: 533] [Impact Index Per Article: 59.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Affiliation(s)
- Christina M. Payne
- Department
of Chemical and Materials Engineering and Center for Computational
Sciences, University of Kentucky, 177 F. Paul Anderson Tower, Lexington, Kentucky 40506, United States
| | - Brandon C. Knott
- National
Bioenergy Center, National Renewable Energy Laboratory, 15013 Denver
West Parkway, Golden, Colorado 80401, United States
| | - Heather B. Mayes
- Department
of Chemical and Biological Engineering, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, United States
| | - Henrik Hansson
- Department
of Chemistry and Biotechnology, Swedish University of Agricultural Sciences, Uppsala BioCenter, Almas allé 5, SE-75651 Uppsala, Sweden
| | - Michael E. Himmel
- Biosciences
Center, National Renewable Energy Laboratory, 15013 Denver West Parkway, Golden, Colorado 80401, United States
| | - Mats Sandgren
- Department
of Chemistry and Biotechnology, Swedish University of Agricultural Sciences, Uppsala BioCenter, Almas allé 5, SE-75651 Uppsala, Sweden
| | - Jerry Ståhlberg
- Department
of Chemistry and Biotechnology, Swedish University of Agricultural Sciences, Uppsala BioCenter, Almas allé 5, SE-75651 Uppsala, Sweden
| | - Gregg T. Beckham
- National
Bioenergy Center, National Renewable Energy Laboratory, 15013 Denver
West Parkway, Golden, Colorado 80401, United States
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103
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Nishijima H, Nozaki K, Mizuno M, Arai T, Amano Y. Extra tyrosine in the carbohydrate-binding module of Irpex lacteus Xyn10B enhances its cellulose-binding ability. Biosci Biotechnol Biochem 2015; 79:738-46. [PMID: 25560084 DOI: 10.1080/09168451.2014.996203] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
The xylanase (Xyn10B) that strongly adsorbs on microcrystalline cellulose was isolated from Driselase. The Xyn10B contains a Carbohydrate-binding module family 1 (CBM1) (IrpCBMXyn10B) at N-terminus. The canonical essential aromatic residues required for cellulose binding were conserved in IrpCBMXyn10B; however, its adsorption ability was markedly higher than that typically observed for the CBM1 of an endoglucanase from Trametes hirsuta (ThCBMEG1). An analysis of the CBM-GFP fusion proteins revealed that the binding capacity to cellulose (7.8 μmol/g) and distribution coefficient (2.0 L/μmol) of IrpCBMXyn10B-GFP were twofold higher than those of ThCBMEG1-GFP (3.4 μmol/g and 1.2 L/μmol, respectively), used as a reference structure. Besides the canonical aromatic residues (W24-Y50-Y51) of typical CBM1-containing proteins, IrpCBMXyn10B had an additional aromatic residue (Y52). The mutation of Y52 to Ser (IrpCBMY52S-GFP) reduced these adsorption parameters to 4.4 μmol/g and 1.5 L/μmol, which were similar to those of ThCBMEG1-GFP. These results indicate that Y52 plays a crucial role in strong cellulose binding.
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Affiliation(s)
- Hiroto Nishijima
- a Department of Bioscience & Textile Technology, Interdisciplinary Graduate School of Science and Technology , Shinshu University , Nagano , Japan
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104
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Vermaas JV, Petridis L, Qi X, Schulz R, Lindner B, Smith JC. Mechanism of lignin inhibition of enzymatic biomass deconstruction. BIOTECHNOLOGY FOR BIOFUELS 2015; 8:217. [PMID: 26697106 PMCID: PMC4687093 DOI: 10.1186/s13068-015-0379-8] [Citation(s) in RCA: 94] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/15/2015] [Accepted: 11/09/2015] [Indexed: 05/06/2023]
Abstract
BACKGROUND The conversion of plant biomass to ethanol via enzymatic cellulose hydrolysis offers a potentially sustainable route to biofuel production. However, the inhibition of enzymatic activity in pretreated biomass by lignin severely limits the efficiency of this process. RESULTS By performing atomic-detail molecular dynamics simulation of a biomass model containing cellulose, lignin, and cellulases (TrCel7A), we elucidate detailed lignin inhibition mechanisms. We find that lignin binds preferentially both to the elements of cellulose to which the cellulases also preferentially bind (the hydrophobic faces) and also to the specific residues on the cellulose-binding module of the cellulase that are critical for cellulose binding of TrCel7A (Y466, Y492, and Y493). CONCLUSIONS Lignin thus binds exactly where for industrial purposes it is least desired, providing a simple explanation of why hydrolysis yields increase with lignin removal.
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Affiliation(s)
- Josh V. Vermaas
- />UT/ORNL Center for Molecular Biophysics, Oak Ridge National Laboratory, 37831 Oak Ridge, TN USA
- />Center for Biophysics and Quantitative Biology, University of Illinois at Urbana-Champaign, 61801 Urbana, IL USA
| | - Loukas Petridis
- />UT/ORNL Center for Molecular Biophysics, Oak Ridge National Laboratory, 37831 Oak Ridge, TN USA
| | - Xianghong Qi
- />UT/ORNL Center for Molecular Biophysics, Oak Ridge National Laboratory, 37831 Oak Ridge, TN USA
- />Department of Biochemistry and Cellular and Molecular Biology, University of Tennessee, 37996 Knoxville, TN USA
| | - Roland Schulz
- />UT/ORNL Center for Molecular Biophysics, Oak Ridge National Laboratory, 37831 Oak Ridge, TN USA
- />Department of Biochemistry and Cellular and Molecular Biology, University of Tennessee, 37996 Knoxville, TN USA
| | - Benjamin Lindner
- />UT/ORNL Center for Molecular Biophysics, Oak Ridge National Laboratory, 37831 Oak Ridge, TN USA
| | - Jeremy. C. Smith
- />UT/ORNL Center for Molecular Biophysics, Oak Ridge National Laboratory, 37831 Oak Ridge, TN USA
- />Department of Biochemistry and Cellular and Molecular Biology, University of Tennessee, 37996 Knoxville, TN USA
- />University of Tennessee/Oak Ridge National Laboratory Center for Molecular Biophysics, P.O.Box 2008, Oak Ridge, TN 37831-6309 USA
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105
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Greene ER, Himmel ME, Beckham GT, Tan Z. Glycosylation of Cellulases: Engineering Better Enzymes for Biofuels. Adv Carbohydr Chem Biochem 2015; 72:63-112. [PMID: 26613815 DOI: 10.1016/bs.accb.2015.08.001] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
Abstract
Cellulose in plant cell walls is the largest reservoir of renewable carbon on Earth. The saccharification of cellulose from plant biomass into soluble sugars can be achieved using fungal and bacterial cellulolytic enzymes, cellulases, and further converted into fuels and chemicals. Most fungal cellulases are both N- and O-glycosylated in their native form, yet the consequences of glycosylation on activity and structure are not fully understood. Studying protein glycosylation is challenging as glycans are extremely heterogeneous, stereochemically complex, and glycosylation is not under direct genetic control. Despite these limitations, many studies have begun to unveil the role of cellulase glycosylation, especially in the industrially relevant cellobiohydrolase from Trichoderma reesei, Cel7A. Glycosylation confers many beneficial properties to cellulases including enhanced activity, thermal and proteolytic stability, and structural stabilization. However, glycosylation must be controlled carefully as such positive effects can be dampened or reversed. Encouragingly, methods for the manipulation of glycan structures have been recently reported that employ genetic tuning of glycan-active enzymes expressed from homogeneous and heterologous fungal hosts. Taken together, these studies have enabled new strategies for the exploitation of protein glycosylation for the production of enhanced cellulases for biofuel production.
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106
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Inoue H, Kishishita S, Kumagai A, Kataoka M, Fujii T, Ishikawa K. Contribution of a family 1 carbohydrate-binding module in thermostable glycoside hydrolase 10 xylanase from Talaromyces cellulolyticus toward synergistic enzymatic hydrolysis of lignocellulose. BIOTECHNOLOGY FOR BIOFUELS 2015; 8:77. [PMID: 26000036 PMCID: PMC4440266 DOI: 10.1186/s13068-015-0259-2] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/17/2015] [Accepted: 04/29/2015] [Indexed: 05/10/2023]
Abstract
BACKGROUND Enzymatic removal of hemicellulose components such as xylan is an important factor for maintaining high glucose conversion from lignocelluloses subjected to low-severity pretreatment. Supplementation of xylanase in the cellulase mixture enhances glucose release from pretreated lignocellulose. Filamentous fungi produce multiple xylanases in their cellulase system, and some of them have modular structures consisting of a catalytic domain and a family 1 carbohydrate-binding module (CBM1). However, the role of CBM1 in xylanase in the synergistic hydrolysis of lignocellulose has not been investigated in depth. RESULTS Thermostable endo-β-1,4-xylanase (Xyl10A) from Talaromyces cellulolyticus, which is recognized as one of the core enzymes in the fungal cellulase system, has a modular structure consisting of a glycoside hydrolase family 10 catalytic domain and CBM1 at the C-terminus separated by a linker region. Three recombinant Xyl10A variants, that is, intact Xyl10A (Xyl10Awt), CBM1-deleted Xyl10A (Xyl10AdC), and CBM1 and linker region-deleted Xyl10A (Xyl10AdLC), were constructed and overexpressed in T. cellulolyticus. Cellulose-binding ability of Xyl10A CBM1 was demonstrated using quartz crystal microbalance with dissipation monitoring. Xyl10AdC and Xyl10AdLC showed relatively high catalytic activities for soluble and insoluble xylan substrates, whereas Xyl10Awt was more effective in xylan hydrolysis of wet disc-mill treated rice straw (WDM-RS). The enzyme mixture of cellulase monocomponents and intact or mutant Xyl10A enhanced the hydrolysis of WDM-RS glucan, with the most efficient synergism found in the interactions with Xyl10Awt. The increased glucan hydrolysis yield exhibited a linear relationship with the xylan hydrolysis yield by each enzyme. This relationship revealed significant hydrolysis of WDM-RS glucan with lower supplementation of Xyl10Awt. CONCLUSIONS Our results suggest that Xyl10A CBM1 has the following two roles in synergistic hydrolysis of lignocellulose by Xyl10A and cellulases: enhancement of lignocellulosic xylan hydrolysis by binding to cellulose, and the efficient removal of xylan obstacles that interrupt the cellulase activity (because of similar binding target of CBM1). The combination of CBM-containing cellulases and xylanases in a fugal cellulase system could contribute to reduction of the enzyme loading in the hydrolysis of pretreated lignocelluloses.
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Affiliation(s)
- Hiroyuki Inoue
- Research Institute for Sustainable Chemistry, National Institute of Advanced Industrial Science and Technology (AIST), 3-11-32 Kagamiyama, Higashi-Hiroshima, Hiroshima 739-0046 Japan
| | - Seiichiro Kishishita
- Research Institute for Sustainable Chemistry, National Institute of Advanced Industrial Science and Technology (AIST), 3-11-32 Kagamiyama, Higashi-Hiroshima, Hiroshima 739-0046 Japan
| | - Akio Kumagai
- Research Institute for Sustainable Chemistry, National Institute of Advanced Industrial Science and Technology (AIST), 3-11-32 Kagamiyama, Higashi-Hiroshima, Hiroshima 739-0046 Japan
| | - Misumi Kataoka
- Research Institute for Sustainable Chemistry, National Institute of Advanced Industrial Science and Technology (AIST), 3-11-32 Kagamiyama, Higashi-Hiroshima, Hiroshima 739-0046 Japan
| | - Tatsuya Fujii
- Research Institute for Sustainable Chemistry, National Institute of Advanced Industrial Science and Technology (AIST), 3-11-32 Kagamiyama, Higashi-Hiroshima, Hiroshima 739-0046 Japan
| | - Kazuhiko Ishikawa
- Research Institute for Sustainable Chemistry, National Institute of Advanced Industrial Science and Technology (AIST), 3-11-32 Kagamiyama, Higashi-Hiroshima, Hiroshima 739-0046 Japan
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107
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Rozman Grinberg I, Yin G, Borovok I, Berg Miller ME, Yeoman CJ, Dassa B, Yu Z, Mizrahi I, Flint HJ, Bayer EA, White BA, Lamed R. Functional phylotyping approach for assessing intraspecific diversity of Ruminococcus albus within the rumen microbiome. FEMS Microbiol Lett 2014; 362:1-10. [PMID: 25673657 DOI: 10.1093/femsle/fnu047] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Ruminococcus albus, a cellulolytic bacterium, is a critical member of the rumen community. Ruminococcus albus lacks a classical cellulosome complex, but it possesses a unique family 37 carbohydrate-binding module (CBM37), which is integrated into a variety of carbohydrate-active enzymes. We developed a potential molecular tool for functional phylotyping of the R. albus population in the rumen, based on a variable region in the cel48A gene. cel48A encodes a single copy of the CBM37-associated family 48 glycoside hydrolase in all known strains of this bacterium. A segment of the cel48A gene was amplified from rumen metagenomic samples of four bovines, and its abundance and diversity were evaluated. Analysis of the obtained sequences revealed the co-existence of multiple functional phylotypes of cel48A in all four animals. These included sequences identical or similar to those of R. albus isolates (reference strains), as well as several novel sequences. The dominant cel48A type varied among animals. This method can be used for detection of intraspecific diversity of R. albus in metagenomic samples. Together with scaC, a previously reported gene marker for R. flavefaciens, we present a set of two species-specific markers for phylotyping of Ruminococci in the herbivore rumen.
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Affiliation(s)
- Inna Rozman Grinberg
- Department of Molecular Microbiology and Biotechnology, Tel Aviv University, Ramat Aviv 69978, Israel
| | - Guohua Yin
- Department of Molecular Microbiology and Biotechnology, Tel Aviv University, Ramat Aviv 69978, Israel
| | - Ilya Borovok
- Department of Molecular Microbiology and Biotechnology, Tel Aviv University, Ramat Aviv 69978, Israel
| | | | - Carl J Yeoman
- Department of Animal and Range Sciences, Montana State University, Bozeman, MT 59717, USA
| | - Bareket Dassa
- Department of Biological Chemistry, The Weizmann Institute of Science, Rehovot 7610001, Israel
| | - Zhongtang Yu
- The MAPLE Research Initiative, Department of Animal Sciences, The Ohio State University, Columbus, OH 43210, USA
| | - Itzhak Mizrahi
- Department of Ruminant Science, Institute of Animal Sciences, Agricultural Research Organization, Bet Dagan 50250, Israel
| | - Harry J Flint
- Rowett Institute of Nutrition and Health, University of Aberdeen, Aberdeen AB21 9SB, UK
| | - Edward A Bayer
- Department of Biological Chemistry, The Weizmann Institute of Science, Rehovot 7610001, Israel
| | - Bryan A White
- Institute for Genomic Biology, University of Illinois, Urbana, IL 61801, USA
| | - Raphael Lamed
- Department of Molecular Microbiology and Biotechnology, Tel Aviv University, Ramat Aviv 69978, Israel
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108
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Gao D, Haarmeyer C, Balan V, Whitehead TA, Dale BE, Chundawat SPS. Lignin triggers irreversible cellulase loss during pretreated lignocellulosic biomass saccharification. BIOTECHNOLOGY FOR BIOFUELS 2014; 7:175. [PMID: 25530803 PMCID: PMC4272552 DOI: 10.1186/s13068-014-0175-x] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/23/2014] [Accepted: 11/27/2014] [Indexed: 05/02/2023]
Abstract
BACKGROUND Non-productive binding of enzymes to lignin is thought to impede the saccharification efficiency of pretreated lignocellulosic biomass to fermentable sugars. Due to a lack of suitable analytical techniques that track binding of individual enzymes within complex protein mixtures and the difficulty in distinguishing the contribution of productive (binding to specific glycans) versus non-productive (binding to lignin) binding of cellulases to lignocellulose, there is currently a poor understanding of individual enzyme adsorption to lignin during the time course of pretreated biomass saccharification. RESULTS In this study, we have utilized an FPLC (fast protein liquid chromatography)-based methodology to quantify free Trichoderma reesei cellulases (namely CBH I, CBH II, and EG I) concentration within a complex hydrolyzate mixture during the varying time course of biomass saccharification. Three pretreated corn stover (CS) samples were included in this study: Ammonia Fiber Expansion(a) (AFEX™-CS), dilute acid (DA-CS), and ionic liquid (IL-CS) pretreatments. The relative fraction of bound individual cellulases varied depending not only on the pretreated biomass type (and lignin abundance) but also on the type of cellulase. Acid pretreated biomass had the highest levels of non-recoverable cellulases, while ionic liquid pretreated biomass had the highest overall cellulase recovery. CBH II has the lowest thermal stability among the three T. reesei cellulases tested. By preparing recombinant family 1 carbohydrate binding module (CBM) fusion proteins, we have shown that family 1 CBMs are highly implicated in the non-productive binding of full-length T. reesei cellulases to lignin. CONCLUSIONS Our findings aid in further understanding the complex mechanisms of non-productive binding of cellulases to pretreated lignocellulosic biomass. Developing optimized pretreatment processes with reduced or modified lignin content to minimize non-productive enzyme binding or engineering pretreatment-specific, low-lignin binding cellulases will improve enzyme specific activity, facilitate enzyme recycling, and thereby permit production of cheaper biofuels.
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Affiliation(s)
- Dahai Gao
- />Department of Chemical Engineering and Materials Science, Michigan State University, East Lansing, MI 48824 USA
- />Great Lakes Bioenergy Research Center (GLBRC), Michigan State University, 164 Food Safety and Toxicology Building, East Lansing, MI 48824 USA
- />Biomass Conversion Research Lab (BCRL), MBI Building, 3900 Collins Road, East Lansing, MI 48910 USA
| | - Carolyn Haarmeyer
- />Department of Chemical Engineering and Materials Science, Michigan State University, East Lansing, MI 48824 USA
| | - Venkatesh Balan
- />Department of Chemical Engineering and Materials Science, Michigan State University, East Lansing, MI 48824 USA
- />Great Lakes Bioenergy Research Center (GLBRC), Michigan State University, 164 Food Safety and Toxicology Building, East Lansing, MI 48824 USA
- />Biomass Conversion Research Lab (BCRL), MBI Building, 3900 Collins Road, East Lansing, MI 48910 USA
| | - Timothy A Whitehead
- />Department of Chemical Engineering and Materials Science, Michigan State University, East Lansing, MI 48824 USA
- />Department of Biosystems and Agricultural Engineering, Michigan State University, East Lansing, MI 48824 USA
| | - Bruce E Dale
- />Department of Chemical Engineering and Materials Science, Michigan State University, East Lansing, MI 48824 USA
- />Great Lakes Bioenergy Research Center (GLBRC), Michigan State University, 164 Food Safety and Toxicology Building, East Lansing, MI 48824 USA
- />Biomass Conversion Research Lab (BCRL), MBI Building, 3900 Collins Road, East Lansing, MI 48910 USA
| | - Shishir PS Chundawat
- />Department of Chemical Engineering and Materials Science, Michigan State University, East Lansing, MI 48824 USA
- />Great Lakes Bioenergy Research Center (GLBRC), Michigan State University, 164 Food Safety and Toxicology Building, East Lansing, MI 48824 USA
- />Biomass Conversion Research Lab (BCRL), MBI Building, 3900 Collins Road, East Lansing, MI 48910 USA
- />Department of Chemical & Biochemical Engineering, Rutgers, The State University of New Jersey, 98 Brett Road, Room C-150A, Piscataway, NJ 08854 USA
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109
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Protein engineering of cellulases. Curr Opin Biotechnol 2014; 29:139-45. [DOI: 10.1016/j.copbio.2014.04.007] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2014] [Revised: 04/06/2014] [Accepted: 04/07/2014] [Indexed: 11/21/2022]
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110
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Jalak J, Väljamäe P. Multi-mode binding of Cellobiohydrolase Cel7A from Trichoderma reesei to cellulose. PLoS One 2014; 9:e108181. [PMID: 25265511 PMCID: PMC4180464 DOI: 10.1371/journal.pone.0108181] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2014] [Accepted: 08/19/2014] [Indexed: 01/26/2023] Open
Abstract
Enzymatic hydrolysis of recalcitrant polysaccharides like cellulose takes place on the solid-liquid interface. Therefore the adsorption of enzymes to the solid surface is a pre-requisite for catalysis. Here we used enzymatic activity measurements with fluorescent model-substrate 4-methyl-umbelliferyl-β-D-lactoside for sensitive monitoring of the binding of cellobiohydrolase TrCel7A from Trichoderma reesei to bacterial cellulose (BC). The binding at low nanomolar free TrCel7A concentrations was exclusively active site mediated and was consistent with Langmuir's one binding site model with Kd and Amax values of 2.9 nM and 126 nmol/g BC, respectively. This is the strongest binding observed with non-complexed cellulases and apparently represents the productive binding of TrCel7A to cellulose chain ends on the hydrophobic face of BC microfibril. With increasing free TrCel7A concentrations the isotherm gradually deviated from the Langmuir's one binding site model. This was caused by the increasing contribution of lower affinity binding modes that included both active site mediated binding and non-productive binding with active site free from cellulose chain. The binding of TrCel7A to BC was found to be only partially reversible. Furthermore, the isotherm was dependent on the concentration of BC with more efficient binding observed at lower BC concentrations. The phenomenon can be ascribed to the BC concentration dependent aggregation of BC microfibrils with concomitant reduction of specific surface area.
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Affiliation(s)
- Jürgen Jalak
- Institute of Molecular and Cell Biology, University of Tartu, Tartu, Estonia
| | - Priit Väljamäe
- Institute of Molecular and Cell Biology, University of Tartu, Tartu, Estonia
- * E-mail:
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111
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Momeni MH, Goedegebuur F, Hansson H, Karkehabadi S, Askarieh G, Mitchinson C, Larenas EA, Ståhlberg J, Sandgren M. Expression, crystal structure and cellulase activity of the thermostable cellobiohydrolase Cel7A from the fungus Humicola grisea var. thermoidea. ACTA CRYSTALLOGRAPHICA. SECTION D, BIOLOGICAL CRYSTALLOGRAPHY 2014; 70:2356-66. [PMID: 25195749 PMCID: PMC4157447 DOI: 10.1107/s1399004714013844] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/26/2014] [Accepted: 06/13/2014] [Indexed: 11/11/2022]
Abstract
Glycoside hydrolase family 7 (GH7) cellobiohydrolases (CBHs) play a key role in biomass recycling in nature. They are typically the most abundant enzymes expressed by potent cellulolytic fungi, and are also responsible for the majority of hydrolytic potential in enzyme cocktails for industrial processing of plant biomass. The thermostability of the enzyme is an important parameter for industrial utilization. In this study, Cel7 enzymes from different fungi were expressed in a fungal host and assayed for thermostability, including Hypocrea jecorina Cel7A as a reference. The most stable of the homologues, Humicola grisea var. thermoidea Cel7A, exhibits a 10°C higher melting temperature (T(m) of 72.5°C) and showed a 4-5 times higher initial hydrolysis rate than H. jecorina Cel7A on phosphoric acid-swollen cellulose and showed the best performance of the tested enzymes on pretreated corn stover at elevated temperature (65°C, 24 h). The enzyme shares 57% sequence identity with H. jecorina Cel7A and consists of a GH7 catalytic module connected by a linker to a C-terminal CBM1 carbohydrate-binding module. The crystal structure of the H. grisea var. thermoidea Cel7A catalytic module (1.8 Å resolution; R(work) and R(free) of 0.16 and 0.21, respectively) is similar to those of other GH7 CBHs. The deviations of several loops along the cellulose-binding path between the two molecules in the asymmetric unit indicate higher flexibility than in the less thermostable H. jecorina Cel7A.
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Affiliation(s)
- Majid Haddad Momeni
- Department of Chemistry and Biotechnology, Swedish University of Agricultural Sciences, PO Box 7015, SE-750 07 Uppsala, Sweden
| | - Frits Goedegebuur
- DuPont, Industrial Biosciences, Archimedesweg 30, 2333 CN Leiden, The Netherlands
| | - Henrik Hansson
- Department of Chemistry and Biotechnology, Swedish University of Agricultural Sciences, PO Box 7015, SE-750 07 Uppsala, Sweden
| | - Saeid Karkehabadi
- Department of Chemistry and Biotechnology, Swedish University of Agricultural Sciences, PO Box 7015, SE-750 07 Uppsala, Sweden
| | - Glareh Askarieh
- Department of Chemistry and Biotechnology, Swedish University of Agricultural Sciences, PO Box 7015, SE-750 07 Uppsala, Sweden
| | - Colin Mitchinson
- DuPont, Industrial Biosciences, Page Mill Road, Palo Alto, CA 94304, USA
| | - Edmundo A. Larenas
- DuPont, Industrial Biosciences, Page Mill Road, Palo Alto, CA 94304, USA
| | - Jerry Ståhlberg
- Department of Chemistry and Biotechnology, Swedish University of Agricultural Sciences, PO Box 7015, SE-750 07 Uppsala, Sweden
| | - Mats Sandgren
- Department of Chemistry and Biotechnology, Swedish University of Agricultural Sciences, PO Box 7015, SE-750 07 Uppsala, Sweden
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112
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113
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Bornscheuer U, Buchholz K, Seibel J. Enzymatic degradation of (ligno)cellulose. Angew Chem Int Ed Engl 2014; 53:10876-93. [PMID: 25136976 DOI: 10.1002/anie.201309953] [Citation(s) in RCA: 65] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2013] [Indexed: 11/06/2022]
Abstract
Glycoside-degrading enzymes play a dominant role in the biochemical conversion of cellulosic biomass into low-price biofuels and high-value-added chemicals. New insight into protein functions and substrate structures, the kinetics of recognition, and degradation events has resulted in a substantial improvement of our understanding of cellulose degradation.
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Affiliation(s)
- Uwe Bornscheuer
- Ernst-Moritz-Arndt-Universität Greifswald, Biotechnologie und Enzymkatalyse, Institut für Biochemie, Felix-Hausdorff-Strasse 4, 17487 Greifswald (Germany)
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114
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Towards a molecular-level theory of carbohydrate processivity in glycoside hydrolases. Curr Opin Biotechnol 2014; 27:96-106. [DOI: 10.1016/j.copbio.2013.12.002] [Citation(s) in RCA: 65] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2013] [Accepted: 12/04/2013] [Indexed: 10/25/2022]
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115
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Bodenheimer AM, Cuneo MJ, Swartz PD, He J, O’Neill HM, Myles DAA, Evans BR, Meilleur F. Crystallization and preliminary X-ray diffraction analysis of Hypocrea jecorina Cel7A in two new crystal forms. Acta Crystallogr F Struct Biol Commun 2014; 70:773-6. [PMID: 24915091 PMCID: PMC4051535 DOI: 10.1107/s2053230x14008851] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2014] [Accepted: 04/17/2014] [Indexed: 11/10/2022] Open
Abstract
Cel7A (previously known as cellobiohydrolase I) from Hypocrea jecorina was crystallized in two crystalline forms, neither of which have been previously reported. Both forms co-crystallize under the same crystallization conditions. The first crystal form belonged to space group C2, with unit-cell parameters a=152.5, b=44.9, c=57.6 Å, β=101.2°, and diffracted X-rays to 1.5 Å resolution. The second crystal form belonged to space group P6₃22, with unit-cell parameters a=b≃155, c≃138 Å, and diffracted X-rays to 2.5 Å resolution. The crystals were obtained using full-length Cel7A, which consists of a large 434-residue N-terminal catalytic domain capable of cleaving cellulose, a 27-residue flexible linker and a small 36-residue C-terminal carbohydrate-binding module (CBM). However, a preliminary analysis of the electron-density maps suggests that the linker and CBM are disordered in both crystal forms. Complete refinement and structure analysis are currently in progress.
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Affiliation(s)
- Annette M. Bodenheimer
- Molecular and Structural Biochemistry Department, North Carolina State University, Raleigh, North Carolina, USA
| | - Matthew J. Cuneo
- Biology and Soft Matter Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee, USA
| | - Paul D. Swartz
- Molecular and Structural Biochemistry Department, North Carolina State University, Raleigh, North Carolina, USA
| | - Junhong He
- Biology and Soft Matter Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee, USA
| | - Hugh M. O’Neill
- Biology and Soft Matter Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee, USA
| | - Dean A. A. Myles
- Biology and Soft Matter Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee, USA
| | - Barbara R. Evans
- Chemical Science Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee, USA
| | - Flora Meilleur
- Molecular and Structural Biochemistry Department, North Carolina State University, Raleigh, North Carolina, USA
- Biology and Soft Matter Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee, USA
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116
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Specificity of O-glycosylation in enhancing the stability and cellulose binding affinity of Family 1 carbohydrate-binding modules. Proc Natl Acad Sci U S A 2014; 111:7612-7. [PMID: 24821760 DOI: 10.1073/pnas.1402518111] [Citation(s) in RCA: 67] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The majority of biological turnover of lignocellulosic biomass in nature is conducted by fungi, which commonly use Family 1 carbohydrate-binding modules (CBMs) for targeting enzymes to cellulose. Family 1 CBMs are glycosylated, but the effects of glycosylation on CBM function remain unknown. Here, the effects of O-mannosylation are examined on the Family 1 CBM from the Trichoderma reesei Family 7 cellobiohydrolase at three glycosylation sites. To enable this work, a procedure to synthesize glycosylated Family 1 CBMs was developed. Subsequently, a library of 20 CBMs was synthesized with mono-, di-, or trisaccharides at each site for comparison of binding affinity, proteolytic stability, and thermostability. The results show that, although CBM mannosylation does not induce major conformational changes, it can increase the thermolysin cleavage resistance up to 50-fold depending on the number of mannose units on the CBM and the attachment site. O-Mannosylation also increases the thermostability of CBM glycoforms up to 16 °C, and a mannose disaccharide at Ser3 seems to have the largest themostabilizing effect. Interestingly, the glycoforms with small glycans at each site displayed higher binding affinities for crystalline cellulose, and the glycoform with a single mannose at each of three positions conferred the highest affinity enhancement of 7.4-fold. Overall, by combining chemical glycoprotein synthesis and functional studies, we show that specific glycosylation events confer multiple beneficial properties on Family 1 CBMs.
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117
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Deciphering the effect of the different N-glycosylation sites on the secretion, activity, and stability of cellobiohydrolase I from Trichoderma reesei. Appl Environ Microbiol 2014; 80:3962-71. [PMID: 24747898 DOI: 10.1128/aem.00261-14] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
N-linked glycosylation modulates and diversifies the structures and functions of the eukaryotic proteome through both intrinsic and extrinsic effects on proteins. We investigated the significance of the three N-linked glycans on the catalytic domain of cellobiohydrolase I (CBH1) from the filamentous fungus Trichoderma reesei in its secretion and activity. While the removal of one or two N-glycosylation sites hardly affected the extracellular secretion of CBH1, eliminating all of the glycosylation sites did induce expression of the unfolded protein response (UPR) target genes, and secretion of this CBH1 variant was severely compromised in a calnexin gene deletion strain. Further characterization of the purified CBH1 variants showed that, compared to Asn270, the thermal reactivity of CBH1 was significantly decreased by removal of either Asn45 or Asn384 glycosylation site during the catalyzed hydrolysis of soluble substrate. Combinatorial loss of these two N-linked glycans further exacerbated the temperature-dependent inactivation. In contrast, this thermal labile property was less severe when hydrolyzing insoluble cellulose. Analysis of the structural integrity of CBH1 variants revealed that removal of N-glycosylation at Asn384 had a more pronounced effect on the integrity of regular secondary structure compared to the loss of Asn45 or Asn270. These data implicate differential roles of N-glycosylation modifications in contributing to the stability of specific functional regions of CBH1 and highlight the potential of improving the thermostability of CBH1 by tuning proper interactions between glycans and functional residues.
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118
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Selig MJ, Thygesen LG, Felby C. Correlating the ability of lignocellulosic polymers to constrain water with the potential to inhibit cellulose saccharification. BIOTECHNOLOGY FOR BIOFUELS 2014; 7:159. [PMID: 25426165 PMCID: PMC4243321 DOI: 10.1186/s13068-014-0159-x] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/19/2014] [Accepted: 10/08/2014] [Indexed: 05/03/2023]
Abstract
BACKGROUND Studies in bioconversions have continuously sought the development of processing strategies to overcome the "close physical association" between plant cell wall polymers thought to significantly contribute to biomass recalcitrance [Adv Space Res 18:251-265, 1996],[ Science 315:804-807, 2007]. To a lesser extent, studies have sought to understand biophysical factors responsible for the resistance of lignocelluloses to enzymatic degradation. Provided here are data supporting our hypothesis that the inhibitory potential of different cell wall polymers towards enzymatic cellulose hydrolysis is related to how much these polymers constrain the water surrounding them. We believe the entropy-reducing constraint imparted to polymer associated water plays a negative role by increasing the probability of detrimental interactions such as junction zone formation and the non-productive binding of enzymes. RESULTS Selected commercial lignocellulose-derived polymers, including hemicelluloses, pectins, and lignin, showed varied potential to inhibit 24-h cellulose conversion by a mix of purified cellobiohydrolase I and β-glucosidase. At low dry matter loadings (0.5% w/w), insoluble hemicelluloses were most inhibitory (reducing conversion relative to cellulose-only controls by about 80%) followed by soluble xyloglucan and wheat arabinoxylan (reductions of about 70% and 55%, respectively), while the lignin and pectins tested were the least inhibitory (approximately 20% reduction). Low field nuclear magnetic resonance (LF-NMR) relaxometry used to observe water-related proton relaxation in saturated polymer suspensions (10% dry solids, w/w) showed spin-spin, T2, relaxation time curves generally approached zero faster for the most inhibitory polymer preparations. The manner of this decline varied between polymers, indicating different biophysical aspects may differentially contribute to overall water constraint in each case. To better compare the LF-NMR data to inhibitory potential, T2 values from monocomponent exponential fits of relaxation curves were used as a measure of overall water constraint. These values generally correlated faster relaxation times (greater water constraint) with greater inhibition of the model cellulase system by the polymers. CONCLUSIONS The presented correlation of cellulase inhibition and proton relaxation data provides support for our water constraint-biomass recalcitrance hypothesis. Deeper investigation into polymer-cellulose-cellulase interactions should help elucidate the types of interactions that may be propagating this correlation. If these observations can be verified to be more than correlative, the hypothesis and data presented suggest that a focus on water-polymer interactions and ways to alter them may help resolve key biological lignocellulose processing bottlenecks.
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Affiliation(s)
- Michael J Selig
- IGN, Faculty of Science, University of Copenhagen, Rolighedsvej 23, 1958 Frederiksberg, Denmark
| | - Lisbeth G Thygesen
- IGN, Faculty of Science, University of Copenhagen, Rolighedsvej 23, 1958 Frederiksberg, Denmark
| | - Claus Felby
- IGN, Faculty of Science, University of Copenhagen, Rolighedsvej 23, 1958 Frederiksberg, Denmark
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119
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Lambertz C, Garvey M, Klinger J, Heesel D, Klose H, Fischer R, Commandeur U. Challenges and advances in the heterologous expression of cellulolytic enzymes: a review. BIOTECHNOLOGY FOR BIOFUELS 2014; 7:135. [PMID: 25356086 PMCID: PMC4212100 DOI: 10.1186/s13068-014-0135-5] [Citation(s) in RCA: 104] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/05/2014] [Accepted: 09/03/2014] [Indexed: 05/03/2023]
Abstract
Second generation biofuel development is increasingly reliant on the recombinant expression of cellulases. Designing or identifying successful expression systems is thus of preeminent importance to industrial progress in the field. Recombinant production of cellulases has been performed using a wide range of expression systems in bacteria, yeasts and plants. In a number of these systems, particularly when using bacteria and plants, significant challenges have been experienced in expressing full-length proteins or proteins at high yield. Further difficulties have been encountered in designing recombinant systems for surface-display of cellulases and for use in consolidated bioprocessing in bacteria and yeast. For establishing cellulase expression in plants, various strategies are utilized to overcome problems, such as the auto-hydrolysis of developing plant cell walls. In this review, we investigate the major challenges, as well as the major advances made to date in the recombinant expression of cellulases across the commonly used bacterial, plant and yeast systems. We review some of the critical aspects to be considered for industrial-scale cellulase production.
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Affiliation(s)
- Camilla Lambertz
- />Institute for Molecular Biotechnology, RWTH Aachen University, Worringerweg 1, 52074 Aachen, Germany
| | - Megan Garvey
- />Institute for Molecular Biotechnology, RWTH Aachen University, Worringerweg 1, 52074 Aachen, Germany
- />Present address: School of Medicine, Deakin University, CSIRO Australian Animal Health Laboratory, 5 Portarlington Rd, Newcomb, VIC 3219 Australia
| | - Johannes Klinger
- />Institute for Molecular Biotechnology, RWTH Aachen University, Worringerweg 1, 52074 Aachen, Germany
| | - Dirk Heesel
- />Institute for Molecular Biotechnology, RWTH Aachen University, Worringerweg 1, 52074 Aachen, Germany
| | - Holger Klose
- />Institute for Molecular Biotechnology, RWTH Aachen University, Worringerweg 1, 52074 Aachen, Germany
- />Present address: Institute for Botany and Molecular Genetics, RWTH Aachen University, Worringerweg 3, 52074 Aachen, Germany
| | - Rainer Fischer
- />Institute for Molecular Biotechnology, RWTH Aachen University, Worringerweg 1, 52074 Aachen, Germany
- />Fraunhofer Institute for Molecular Biology and Applied Ecology, Forckenbeckstrasse 6, 52074 Aachen, Germany
| | - Ulrich Commandeur
- />Institute for Molecular Biotechnology, RWTH Aachen University, Worringerweg 1, 52074 Aachen, Germany
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120
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Wu M, Bu L, Vuong TV, Wilson DB, Crowley MF, Sandgren M, Ståhlberg J, Beckham GT, Hansson H. Loop motions important to product expulsion in the Thermobifida fusca glycoside hydrolase family 6 cellobiohydrolase from structural and computational studies. J Biol Chem 2013; 288:33107-17. [PMID: 24085303 DOI: 10.1074/jbc.m113.502765] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Cellobiohydrolases (CBHs) are typically major components of natural enzyme cocktails for biomass degradation. Their active sites are enclosed in a tunnel, enabling processive hydrolysis of cellulose chains. Glycoside hydrolase Family 6 (GH6) CBHs act from nonreducing ends by an inverting mechanism and are present in many cellulolytic fungi and bacteria. The bacterial Thermobifida fusca Cel6B (TfuCel6B) exhibits a longer and more enclosed active site tunnel than its fungal counterparts. Here, we determine the structures of two TfuCel6B mutants co-crystallized with cellobiose, D274A (catalytic acid), and the double mutant D226A/S232A, which targets the putative catalytic base and a conserved serine that binds the nucleophilic water. The ligand binding and the structure of the active site are retained when compared with the wild type structure, supporting the hypothesis that these residues are directly involved in catalysis. One structure exhibits crystallographic waters that enable construction of a model of the α-anomer product after hydrolysis. Interestingly, the product sites of TfuCel6B are completely enclosed by an "exit loop" not present in fungal GH6 CBHs and by an extended "bottom loop". From the structures, we hypothesize that either of the loops enclosing the product subsites in the TfuCel6B active site tunnel must open substantially for product release. With simulation, we demonstrate that both loops can readily open to allow product release with equal probability in solution or when the enzyme is engaged on cellulose. Overall, this study reveals new structural details of GH6 CBHs likely important for functional differences among enzymes from this important family.
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Affiliation(s)
- Miao Wu
- From the Department of Molecular Biology, Swedish University of Agricultural Sciences, SE-75007 Uppsala, Sweden
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