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Rational protein engineering of α-L-arabinofuranosidase from Aspergillus niger for improved catalytic hydrolysis efficiency on kenaf hemicellulose. Process Biochem 2021. [DOI: 10.1016/j.procbio.2020.12.012] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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2
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Cellulose as Potential Feedstock for Cellulase Enzyme Production: Versatility and Properties of Various Cellulosic Biomass – Part II. Fungal Biol 2019. [DOI: 10.1007/978-3-030-14726-6_7] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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3
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Lopes A, Ferreira Filho E, Moreira L. An update on enzymatic cocktails for lignocellulose breakdown. J Appl Microbiol 2018; 125:632-645. [DOI: 10.1111/jam.13923] [Citation(s) in RCA: 93] [Impact Index Per Article: 15.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2017] [Revised: 03/20/2018] [Accepted: 05/14/2018] [Indexed: 12/01/2022]
Affiliation(s)
- A.M. Lopes
- Laboratory of Enzymology; Department of Cellular Biology; University of Brasília; Brasilia DF Brazil
| | - E.X. Ferreira Filho
- Laboratory of Enzymology; Department of Cellular Biology; University of Brasília; Brasilia DF Brazil
| | - L.R.S. Moreira
- Laboratory of Enzymology; Department of Cellular Biology; University of Brasília; Brasilia DF Brazil
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4
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Kumar D, Murthy GS. Development and validation of a stochastic molecular model of cellulose hydrolysis by action of multiple cellulase enzymes. BIORESOUR BIOPROCESS 2017. [DOI: 10.1186/s40643-017-0184-2] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
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5
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Kim SK, Chung D, Himmel ME, Bomble YJ, Westpheling J. In vivo synergistic activity of a CAZyme cassette from Acidothermus cellulolyticus significantly improves the cellulolytic activity of the C. bescii exoproteome. Biotechnol Bioeng 2017. [PMID: 28650071 DOI: 10.1002/bit.26366] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
The use of microbial cells to convert plant biomass directly to fuels and chemicals is referred to as consolidated bioprocessing (CBP). Members of the bacterial genus, Caldicellulosiruptor (Gram-positive, anaerobic hyperthermophiles) are capable of deconstructing plant biomass without enzymatic or chemical pretreatment. This is accomplished by the production and secretion of free, multi-domain enzymes that outperform commercial enzyme cocktails on some substrates. Here, we show that the exoproteome of Caldicellulosiruptor bescii may be enhanced by the heterologous expression of enzymes from Acidothermus cellulolyticus that act synergistically to improve sugar release from complex substrates; as well as improve cell growth. In this work, co-expression of the A. cellulolyticus Acel_0615 β-glucanase (GH6 and GH12) and E1 endoglucanase (GH5) enzymes resulted in an increase in the activity of the exoproteome on Avicel; as well as an increase in growth of C. bescii on Avicel compared to the parental strain or the strain expressing the β-glucanase alone. Our ability to engineer the composition and effectiveness of the exoproteome of these bacteria provides insight into the natural mechanism of plant cell wall deconstruction, as well as future directions for improving CBP. Biotechnol. Bioeng. 2017;114: 2474-2480. © 2017 Wiley Periodicals, Inc.
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Affiliation(s)
- Sun-Ki Kim
- Department of Genetics, University of Georgia, Athens, Georgia, 30602.,The BioEnergy Science Center, Oak Ridge National Laboratory, Oak Ridge, Tennessee, 37831
| | - Daehwan Chung
- The BioEnergy Science Center, Oak Ridge National Laboratory, Oak Ridge, Tennessee, 37831.,Biosciences Center, National Renewable Energy Laboratory, Golden, Colorado
| | - Michael E Himmel
- The BioEnergy Science Center, Oak Ridge National Laboratory, Oak Ridge, Tennessee, 37831.,Biosciences Center, National Renewable Energy Laboratory, Golden, Colorado
| | - Yannick J Bomble
- The BioEnergy Science Center, Oak Ridge National Laboratory, Oak Ridge, Tennessee, 37831.,Biosciences Center, National Renewable Energy Laboratory, Golden, Colorado
| | - Janet Westpheling
- Department of Genetics, University of Georgia, Athens, Georgia, 30602.,The BioEnergy Science Center, Oak Ridge National Laboratory, Oak Ridge, Tennessee, 37831
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6
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Guo ZP, Duquesne S, Bozonnet S, Cioci G, Nicaud JM, Marty A, O’Donohue MJ. Conferring cellulose-degrading ability to Yarrowia lipolytica to facilitate a consolidated bioprocessing approach. BIOTECHNOLOGY FOR BIOFUELS 2017; 10:132. [PMID: 28533816 PMCID: PMC5438512 DOI: 10.1186/s13068-017-0819-8] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/14/2017] [Accepted: 05/13/2017] [Indexed: 05/24/2023]
Abstract
BACKGROUND Yarrowia lipolytica, one of the most widely studied "nonconventional" oleaginous yeast species, is unable to grow on cellulose. Recently, we identified and overexpressed two endogenous β-glucosidases in Y. lipolytica, thus enabling this yeast to use cello-oligosaccharides as a carbon source for growth. Using this engineered yeast platform, we have now gone further toward building a fully cellulolytic Y. lipolytica for use in consolidated bioprocessing of cellulose. RESULTS Initially, different essential enzyme components of a cellulase cocktail (i.e,. cellobiohydrolases and endoglucanases) were individually expressed in Y. lipolytica in order to ascertain the viability of the strategy. Accordingly, the Trichoderma reesei endoglucanase I (TrEG I) and II (TrEG II) were secreted as active proteins in Y. lipolytica, with the secretion yield of EG II being twice that of EG I. Characterization of the purified His-tagged recombinant EG proteins (rhTrEGs) revealed that rhTrEG I displayed higher specific activity than rhTrEG II on both cellotriose and insoluble cellulosic substrates, such as Avicel, β-1, 3 glucan, β-1, 4 glucan, and PASC. Similarly, cellobiohydrolases, such as T. reesei CBH I and II (TrCBH I and II), and the CBH I from Neurospora crassa (NcCBH I) were successfully expressed in Y. lipolytica. However, the yield of the expressed TrCBH I was low, so work on this was not pursued. Contrastingly, rhNcCBH I was not only well expressed, but also highly active on PASC and more active on Avicel (0.11 U/mg) than wild-type TrCBH I (0.065 U/mg). Therefore, work was pursued using a combination of NcCBH I and TrCBH II. The quantification of enzyme levels in culture supernatants revealed that the use of a hybrid promoter instead of the primarily used TEF promoter procured four and eight times more NcCBH I and TrCBH II expressions, respectively. Finally, the coexpression of the previously described Y. lipolytica β-glucosidases, the CBH II, and EG I and II from T. reesei, and the N. crassa CBH I procured an engineered Y. lipolytica strain that was able to grow both on model cellulose substrates, such as highly crystalline Avicel, and on industrial cellulose pulp, such as that obtained using an organosolv process. CONCLUSIONS A Y. lipolytica strain coexpressing six cellulolytic enzyme components has been successfully developed. In addition, the results presented show how the recombinant strain can be optimized, for example, using artificial promoters to tailor expression levels. Most significantly, this study has provided a demonstration of how the strain can grow on a sample of industrial cellulose as sole carbon source, thus revealing the feasibility of Yarrowia-based consolidated bioprocess for the production of fuel and chemical precursors. Further, enzyme and strain optimization, coupled to appropriate process design, will undoubtedly lead to much better performances in the future.
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Affiliation(s)
- Zhong-peng Guo
- Biocatalysis Group, INSA/INRA UMR 792, CNRS, LISBP, Université de Toulouse, 135, Avenue de Rangueil, 31077 Toulouse, France
| | - Sophie Duquesne
- Biocatalysis Group, INSA/INRA UMR 792, CNRS, LISBP, Université de Toulouse, 135, Avenue de Rangueil, 31077 Toulouse, France
| | - Sophie Bozonnet
- Biocatalysis Group, INSA/INRA UMR 792, CNRS, LISBP, Université de Toulouse, 135, Avenue de Rangueil, 31077 Toulouse, France
| | - Gianluca Cioci
- Biocatalysis Group, INSA/INRA UMR 792, CNRS, LISBP, Université de Toulouse, 135, Avenue de Rangueil, 31077 Toulouse, France
| | - Jean-Marc Nicaud
- Micalis Institute, INRA, AgroParisTech, Université Paris-Saclay, Jouy-en-Josas, France
| | - Alain Marty
- Biocatalysis Group, INSA/INRA UMR 792, CNRS, LISBP, Université de Toulouse, 135, Avenue de Rangueil, 31077 Toulouse, France
| | - Michael Joseph O’Donohue
- Biocatalysis Group, INSA/INRA UMR 792, CNRS, LISBP, Université de Toulouse, 135, Avenue de Rangueil, 31077 Toulouse, France
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7
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Chylenski P, Forsberg Z, Ståhlberg J, Várnai A, Lersch M, Bengtsson O, Sæbø S, Horn SJ, Eijsink VGH. Development of minimal enzyme cocktails for hydrolysis of sulfite-pulped lignocellulosic biomass. J Biotechnol 2017; 246:16-23. [PMID: 28219736 DOI: 10.1016/j.jbiotec.2017.02.009] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2016] [Revised: 01/26/2017] [Accepted: 02/13/2017] [Indexed: 01/02/2023]
Abstract
Despite recent progress, saccharification of lignocellulosic biomass is still a major cost driver in biorefining. In this study, we present the development of minimal enzyme cocktails for hydrolysis of Norway spruce and sugarcane bagasse, which were pretreated using the so-called BALI™ process, which is based on sulfite pulping technology. Minimal enzyme cocktails were composed using several glycoside hydrolases purified from the industrially relevant filamentous fungus Trichoderma reesei and a purified commercial β-glucosidase from Aspergillus niger. The contribution of in-house expressed lytic polysaccharide monooxygenases (LPMOs) was also tested, since oxidative cleavage of cellulose by such LPMOs is known to be beneficial for conversion efficiency. We show that the optimized cocktails permit efficient saccharification at reasonable enzyme loadings and that the effect of the LPMOs is substrate-dependent. Using a cocktail comprising only four enzymes, glucan conversion for Norway spruce reached >80% at enzyme loadings of 8mg/g glucan, whereas almost 100% conversion was achieved at 16mg/g.
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Affiliation(s)
- Piotr Chylenski
- Department of Chemistry, Biotechnology and Food Science, Norwegian University of Life Sciences (NMBU), Ås, Norway
| | - Zarah Forsberg
- Department of Chemistry, Biotechnology and Food Science, Norwegian University of Life Sciences (NMBU), Ås, Norway
| | - Jerry Ståhlberg
- Department of Chemistry and Biotechnology, Swedish University of Agricultural Sciences, Uppsala, Sweden
| | - Anikó Várnai
- Department of Chemistry, Biotechnology and Food Science, Norwegian University of Life Sciences (NMBU), Ås, Norway
| | | | | | - Solve Sæbø
- Department of Chemistry, Biotechnology and Food Science, Norwegian University of Life Sciences (NMBU), Ås, Norway
| | - Svein Jarle Horn
- Department of Chemistry, Biotechnology and Food Science, Norwegian University of Life Sciences (NMBU), Ås, Norway
| | - Vincent G H Eijsink
- Department of Chemistry, Biotechnology and Food Science, Norwegian University of Life Sciences (NMBU), Ås, Norway.
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Biochemical and Structural Characterizations of Two Dictyostelium Cellobiohydrolases from the Amoebozoa Kingdom Reveal a High Level of Conservation between Distant Phylogenetic Trees of Life. Appl Environ Microbiol 2016; 82:3395-409. [PMID: 27037126 DOI: 10.1128/aem.00163-16] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2016] [Accepted: 03/25/2016] [Indexed: 12/26/2022] Open
Abstract
UNLABELLED Glycoside hydrolase family 7 (GH7) cellobiohydrolases (CBHs) are enzymes commonly employed in plant cell wall degradation across eukaryotic kingdoms of life, as they provide significant hydrolytic potential in cellulose turnover. To date, many fungal GH7 CBHs have been examined, yet many questions regarding structure-activity relationships in these important natural and commercial enzymes remain. Here, we present the crystal structures and a biochemical analysis of two GH7 CBHs from social amoeba: Dictyostelium discoideum Cel7A (DdiCel7A) and Dictyostelium purpureum Cel7A (DpuCel7A). DdiCel7A and DpuCel7A natively consist of a catalytic domain and do not exhibit a carbohydrate-binding module (CBM). The structures of DdiCel7A and DpuCel7A, resolved to 2.1 Å and 2.7 Å, respectively, are homologous to those of other GH7 CBHs with an enclosed active-site tunnel. Two primary differences between the Dictyostelium CBHs and the archetypal model GH7 CBH, Trichoderma reesei Cel7A (TreCel7A), occur near the hydrolytic active site and the product-binding sites. To compare the activities of these enzymes with the activity of TreCel7A, the family 1 TreCel7A CBM and linker were added to the C terminus of each of the Dictyostelium enzymes, creating DdiCel7ACBM and DpuCel7ACBM, which were recombinantly expressed in T. reesei DdiCel7ACBM and DpuCel7ACBM hydrolyzed Avicel, pretreated corn stover, and phosphoric acid-swollen cellulose as efficiently as TreCel7A when hydrolysis was compared at their temperature optima. The Ki of cellobiose was significantly higher for DdiCel7ACBM and DpuCel7ACBM than for TreCel7A: 205, 130, and 29 μM, respectively. Taken together, the present study highlights the remarkable degree of conservation of the activity of these key natural and industrial enzymes across quite distant phylogenetic trees of life. IMPORTANCE GH7 CBHs are among the most important cellulolytic enzymes both in nature and for emerging industrial applications for cellulose breakdown. Understanding the diversity of these key industrial enzymes is critical to engineering them for higher levels of activity and greater stability. The present work demonstrates that two GH7 CBHs from social amoeba are surprisingly quite similar in structure and activity to the canonical GH7 CBH from the model biomass-degrading fungus T. reesei when tested under equivalent conditions (with added CBM-linker domains) on an industrially relevant substrate.
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9
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Fungal Biotechnology for Industrial Enzyme Production: Focus on (Hemi)cellulase Production Strategies, Advances and Challenges. Fungal Biol 2016. [DOI: 10.1007/978-3-319-27951-0_19] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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10
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Linger JG, Taylor LE, Baker JO, Vander Wall T, Hobdey SE, Podkaminer K, Himmel ME, Decker SR. A constitutive expression system for glycosyl hydrolase family 7 cellobiohydrolases in Hypocrea jecorina. BIOTECHNOLOGY FOR BIOFUELS 2015; 8:45. [PMID: 25904982 PMCID: PMC4405872 DOI: 10.1186/s13068-015-0230-2] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/26/2015] [Accepted: 02/23/2015] [Indexed: 05/23/2023]
Abstract
BACKGROUND One of the primary industrial-scale cellulase producers is the ascomycete fungus, Hypocrea jecorina, which produces and secretes large quantities of diverse cellulolytic enzymes. Perhaps the single most important biomass degrading enzyme is cellobiohydrolase I (cbh1or Cel7A) due to its enzymatic proficiency in cellulose depolymerization. However, production of Cel7A with native-like properties from heterologous expression systems has proven difficult. In this study, we develop a protein expression system in H. jecorina (Trichoderma reesei) useful for production and secretion of heterologous cellobiohydrolases from glycosyl hydrolase family 7. Building upon previous work in heterologous protein expression in filamentous fungi, we have integrated a native constitutive enolase promoter with the native cbh1 signal sequence. RESULTS The constitutive eno promoter driving the expression of Cel7A allows growth on glucose and results in repression of the native cellulase system, severely reducing background endo- and other cellulase activity and greatly simplifying purification of the recombinant protein. Coupling this system to a Δcbh1 strain of H. jecorina ensures that only the recombinant Cel7A protein is produced. Two distinct transformant colony morphologies were observed and correlated with high and null protein production. Production levels in 'fast' transformants are roughly equivalent to those in the native QM6a strain of H. jecorina, typically in the range of 10 to 30 mg/L when grown in continuous stirred-tank fermenters. 'Slow' transformants showed no evidence of Cel7A production. Specific activity of the purified recombinant Cel7A protein is equivalent to that of native protein when assayed on pretreated corn stover, as is the thermal stability and glycosylation level. Purified Cel7A produced from growth on glucose demonstrated remarkably consistent specific activity. Purified Cel7A from the same strain grown on lactose demonstrated significantly higher variability in activity. CONCLUSIONS The elimination of background cellulase induction provides much more consistent measured specific activity compared to a traditional cbh1 promoter system induced with lactose. This expression system provides a powerful tool for the expression and comparison of mutant and/or phylogenetically diverse cellobiohydrolases in the industrially relevant cellulase production host H. jecorina.
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Affiliation(s)
- Jeffrey G Linger
- />National Bioenergy Center, National Renewable Energy Laboratory, 16253 Denver West Parkway, Golden, CO 80401 USA
| | - Larry E Taylor
- />Biosciences Center, National Renewable Energy Laboratory, 16253 Denver West Parkway, Golden, CO 80401 USA
| | - John O Baker
- />Biosciences Center, National Renewable Energy Laboratory, 16253 Denver West Parkway, Golden, CO 80401 USA
| | - Todd Vander Wall
- />Biosciences Center, National Renewable Energy Laboratory, 16253 Denver West Parkway, Golden, CO 80401 USA
| | - Sarah E Hobdey
- />Biosciences Center, National Renewable Energy Laboratory, 16253 Denver West Parkway, Golden, CO 80401 USA
| | - Kara Podkaminer
- />Biosciences Center, National Renewable Energy Laboratory, 16253 Denver West Parkway, Golden, CO 80401 USA
| | - Michael E Himmel
- />Biosciences Center, National Renewable Energy Laboratory, 16253 Denver West Parkway, Golden, CO 80401 USA
| | - Stephen R Decker
- />Biosciences Center, National Renewable Energy Laboratory, 16253 Denver West Parkway, Golden, CO 80401 USA
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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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12
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Chung D, Young J, Cha M, Brunecky R, Bomble YJ, Himmel ME, Westpheling J. Expression of the Acidothermus cellulolyticus E1 endoglucanase in Caldicellulosiruptor bescii enhances its ability to deconstruct crystalline cellulose. BIOTECHNOLOGY FOR BIOFUELS 2015; 8:113. [PMID: 26269712 PMCID: PMC4533959 DOI: 10.1186/s13068-015-0296-x] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/20/2015] [Accepted: 07/24/2015] [Indexed: 05/08/2023]
Abstract
BACKGROUND The Caldicellulosiruptor bescii genome encodes a potent set of carbohydrate-active enzymes (CAZymes), found primarily as multi-domain enzymes that exhibit high cellulolytic and hemicellulolytic activity on and allow utilization of a broad range of substrates, including plant biomass without conventional pretreatment. CelA, the most abundant cellulase in the C. bescii secretome, uniquely combines a GH9 endoglucanase and a GH48 exoglucanase in one protein. The most effective commercial enzyme cocktails used in vitro to pretreat biomass are derived from fungal cellulases (cellobiohydrolases, endoglucanases and a β-d-glucosidases) that act synergistically to release sugars for microbial conversion. The C. bescii genome contains six GH5 domains in five different open reading frames. Four exist in multi-domain proteins and two as single catalytic domains. E1 is a GH5 endoglucanase reported to have high specific activity and simple architecture and is active at the growth temperature of C. bescii. E1 is an endo-1,4-β-glucanase linked to a family 2 carbohydrate-binding module shown to bind primarily to cellulosic substrates. We tested if the addition of this protein to the C. bescii secretome would improve its cellulolytic activity. RESULTS In vitro analysis of E1 and CelA shows synergistic interaction. The E1 gene from Acidothermus cellulolyticus was cloned and expressed in C. bescii under the transcriptional control of the C. bescii S-layer promoter, and secretion was directed by the addition of the C. bescii CelA signal peptide sequence. The vector was integrated into the C. bescii chromosome at a site previously showing no detectable detrimental consequence. Increased activity of the secretome of the strain containing E1 was observed on both carboxymethylcellulose (CMC) and Avicel. Activity against CMC increased on average 10.8 % at 65 °C and 12.6 % at 75 °C. Activity against Avicel increased on average 17.5 % at 65 °C and 16.4 % at 75 °C. CONCLUSIONS Expression and secretion of E1 in C. bescii enhanced the cellulolytic ability of its secretome. These data agree with in vitro evidence that E1 acts synergistically with CelA to digest cellulose and offer the possibility of engineering additional enzymes for improved biomass deconstruction with the knowledge that C. bescii can express a gene from Acidothermus, and perhaps other heterologous genes, effectively.
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Affiliation(s)
- Daehwan Chung
- />Department of Genetics, University of Georgia, Athens, GA USA
- />Oak Ridge National Laboratory, The BioEnergy Science Center, Oak Ridge, TN USA
| | - Jenna Young
- />Department of Genetics, University of Georgia, Athens, GA USA
- />Oak Ridge National Laboratory, The BioEnergy Science Center, Oak Ridge, TN USA
| | - Minseok Cha
- />Department of Genetics, University of Georgia, Athens, GA USA
- />Oak Ridge National Laboratory, The BioEnergy Science Center, Oak Ridge, TN USA
| | - Roman Brunecky
- />National Renewable Energy Laboratory, Biosciences Center, Golden, CO USA
- />Oak Ridge National Laboratory, The BioEnergy Science Center, Oak Ridge, TN USA
| | - Yannick J Bomble
- />National Renewable Energy Laboratory, Biosciences Center, Golden, CO USA
- />Oak Ridge National Laboratory, The BioEnergy Science Center, Oak Ridge, TN USA
| | - Michael E Himmel
- />National Renewable Energy Laboratory, Biosciences Center, Golden, CO USA
- />Oak Ridge National Laboratory, The BioEnergy Science Center, Oak Ridge, TN USA
| | - Janet Westpheling
- />Department of Genetics, University of Georgia, Athens, GA USA
- />Oak Ridge National Laboratory, The BioEnergy Science Center, Oak Ridge, TN USA
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Assessment of field-grown cellulase-expressing corn. Transgenic Res 2014; 24:185-98. [PMID: 25245059 DOI: 10.1007/s11248-014-9838-4] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2014] [Accepted: 09/11/2014] [Indexed: 10/24/2022]
Abstract
Transgenic plants in the US and abroad generated using genetic engineering technology are regulated with respect to release into the environment and inclusion into diets of humans and animals. For crops incorporating pharmaceuticals or industrial enzymes regulations are even more stringent. Notifications are not allowed for movement and release, therefore a permit is required. However, growing under permit is cumbersome and more expensive than open, non- regulated growth. Thus, when the genetically engineered pharmaceutical or industrial crop is ready for scale-up, achieving non-regulated status is critical. Regulatory compliance in the US comprises petitioning the appropriate agencies for permission for environmental release and feeding trials. For release without yearly permits, a petition for allowing non-regulated status can be filed with the United States Department of Agriculture with consultations that include the Food and Drug Administration and possibly the Environmental Protection Agency, the latter if the plant includes an incorporated pesticide. The data package should ensure that the plants are substantially equivalent in every parameter except for the engineered trait. We undertook a preliminary study on transgenic maize field-grown hybrids that express one of two cellulase genes, an exo-cellulase or an endo-cellulase. We performed field observations of whole plants and numerous in vitro analyses of grain. Although some minor differences were observed when comparing genetically engineered hybrid plants to control wild type hybrids, no significant differences were seen.
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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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Trudeau DL, Lee TM, Arnold FH. Engineered thermostable fungal cellulases exhibit efficient synergistic cellulose hydrolysis at elevated temperatures. Biotechnol Bioeng 2014; 111:2390-7. [DOI: 10.1002/bit.25308] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2014] [Revised: 05/28/2014] [Accepted: 06/02/2014] [Indexed: 11/07/2022]
Affiliation(s)
- Devin L. Trudeau
- Division of Chemistry and Chemical Engineering; California Institute of Technology; Pasadena California
| | - Toni M. Lee
- Division of Biology and Bioengineering; California Institute of Technology; Pasadena California
| | - Frances H. Arnold
- Division of Chemistry and Chemical Engineering; California Institute of Technology; Pasadena California
- Division of Biology and Bioengineering; California Institute of Technology; Pasadena California
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16
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Brunecky R, Alahuhta M, Xu Q, Donohoe BS, Crowley MF, Kataeva IA, Yang SJ, Resch MG, Adams MWW, Lunin VV, Himmel ME, Bomble YJ. Response to Comment on "Revealing nature's cellulase diversity: the digestion mechanism of Caldicellulosiruptor bescii CelA". Science 2014; 344:578. [PMID: 24812382 DOI: 10.1126/science.1251701] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Gusakov critiques our methodology for comparing the cellulolytic activity of the bacterial cellulase CelA with the fungal cellulase Cel7A. We address his concerns by clarifying some misconceptions, carefully referencing the literature, and justifying our approach to point out that the results from our study still stand.
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Affiliation(s)
- Roman Brunecky
- Biosciences Center, National Renewable Energy Laboratory, 15013 Denver West Parkway, Golden, CO 80401, USA
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17
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Brunecky R, Alahuhta M, Xu Q, Donohoe BS, Crowley MF, Kataeva IA, Yang SJ, Resch MG, Adams MWW, Lunin VV, Himmel ME, Bomble YJ. Revealing Nature's Cellulase Diversity: The Digestion Mechanism of Caldicellulosiruptor bescii CelA. Science 2013; 342:1513-6. [PMID: 24357319 DOI: 10.1126/science.1244273] [Citation(s) in RCA: 229] [Impact Index Per Article: 20.8] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Affiliation(s)
- Roman Brunecky
- Biosciences Center, National Renewable Energy Laboratory, 15013 Denver West Parkway, Golden, CO 80401, USA
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18
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Heterologous expression of cellobiohydrolase II (Cel6A) in maize endosperm. Transgenic Res 2012; 22:477-88. [PMID: 23080294 DOI: 10.1007/s11248-012-9659-2] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2012] [Accepted: 09/21/2012] [Indexed: 10/27/2022]
Abstract
The technology of converting lignocellulose to biofuels has advanced swiftly over the past few years, and enzymes are a significant constituent of this technology. In this regard, cost effective production of cellulases has been the focus of research for many years. One approach to reach cost targets of these enzymes involves the use of plants as bio-factories. The application of this technology to plant biomass conversion for biofuels and biobased products has the potential for significantly lowering the cost of these products due to lower enzyme production costs. Cel6A, one of the two cellobiohydrolases (CBH II) produced by Hypocrea jecorina, is an exoglucanase that cleaves primarily cellobiose units from the non-reducing end of cellulose microfibrils. In this work we describe the expression of Cel6A in maize endosperm as part of the process to lower the cost of this dominant enzyme for the bioconversion process. The enzyme is active on microcrystalline cellulose as exponential microbial growth was observed in the mixture of cellulose, cellulases, yeast and Cel6A, Cel7A (endoglucanase), and Cel5A (cellobiohydrolase I) expressed in maize seeds. We quantify the amount accumulated and the activity of the enzyme. Cel6A expressed in maize endosperm was purified to homogeneity and verified using peptide mass finger printing.
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Engel P, Krull S, Seiferheld B, Spiess AC. Rational approach to optimize cellulase mixtures for hydrolysis of regenerated cellulose containing residual ionic liquid. BIORESOURCE TECHNOLOGY 2012; 115:27-34. [PMID: 22100231 DOI: 10.1016/j.biortech.2011.10.080] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/02/2011] [Revised: 10/20/2011] [Accepted: 10/22/2011] [Indexed: 05/31/2023]
Abstract
For the efficient production of glucose for platform chemicals or biofuels, cellulosic biomass is pretreated and subsequently hydrolyzed with cellulases. Although ionic liquids (IL) are known to effectively pretreat cellulosic biomass, the hydrolysis of IL pretreated biomass has not been optimized so far. Here, we present a semi-empirical model to rationally optimize the hydrolysis of pretreated α-cellulose - regenerated from IL and containing residual IL from the pretreatment. First, the influence of the IL MMIM DMP on the individual cellulases endoglucanase I, cellobiohydrolase I and β-glucosidase was investigated. Second, an enzyme loading-dependent model was developed to describe kinetics for the individual cellulases and cellulase mixtures. Third, this model was used to optimize the cellulase mixture for the efficient hydrolysis of regenerated cellulose containing residual IL. Finally, we could significantly increase the initial hydrolysis rate in 10% (v/v) MMIM DMP by 49% and the sugar yield by 10% points.
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Affiliation(s)
- Philip Engel
- AVT-Enzyme Process Technology, RWTH Aachen University, Aachen, Germany
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20
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Segato F, Damasio ARL, Gonçalves TA, Murakami MT, Squina FM, Polizeli M, Mort AJ, Prade RA. Two structurally discrete GH7-cellobiohydrolases compete for the same cellulosic substrate fiber. BIOTECHNOLOGY FOR BIOFUELS 2012; 5:21. [PMID: 22494694 PMCID: PMC3431977 DOI: 10.1186/1754-6834-5-21] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/14/2011] [Accepted: 03/30/2012] [Indexed: 05/14/2023]
Abstract
BACKGROUND Cellulose consisting of arrays of linear beta-1,4 linked glucans, is the most abundant carbon-containing polymer present in biomass. Recalcitrance of crystalline cellulose towards enzymatic degradation is widely reported and is the result of intra- and inter-molecular hydrogen bonds within and among the linear glucans. Cellobiohydrolases are enzymes that attack crystalline cellulose. Here we report on two forms of glycosyl hydrolase family 7 cellobiohydrolases common to all Aspergillii that attack Avicel, cotton cellulose and other forms of crystalline cellulose. RESULTS Cellobiohydrolases Cbh1 and CelD have similar catalytic domains but only Cbh1 contains a carbohydrate-binding domain (CBD) that binds to cellulose. Structural superpositioning of Cbh1 and CelD on the Talaromyces emersonii Cel7A 3-dimensional structure, identifies the typical tunnel-like catalytic active site while Cbh1 shows an additional loop that partially obstructs the substrate-fitting channel. CelD does not have a CBD and shows a four amino acid residue deletion on the tunnel-obstructing loop providing a continuous opening in the absence of a CBD. Cbh1 and CelD are catalytically functional and while specific activity against Avicel is 7.7 and 0.5 U.mg prot-1, respectively specific activity on pNPC is virtually identical. Cbh1 is slightly more stable to thermal inactivation compared to CelD and is much less sensitive to glucose inhibition suggesting that an open tunnel configuration, or absence of a CBD, alters the way the catalytic domain interacts with the substrate. Cbh1 and CelD enzyme mixtures on crystalline cellulosic substrates show a strong combinatorial effort response for mixtures where Cbh1 is present in 2:1 or 4:1 molar excess. When CelD was overrepresented the combinatorial effort could only be partially overcome. CelD appears to bind and hydrolyze only loose cellulosic chains while Cbh1 is capable of opening new cellulosic substrate molecules away from the cellulosic fiber. CONCLUSION Cellobiohydrolases both with and without a CBD occur in most fungal genomes where both enzymes are secreted, and likely participate in cellulose degradation. The fact that only Cbh1 binds to the substrate and in combination with CelD exhibits strong synergy only when Cbh1 is present in excess, suggests that Cbh1 unties enough chains from cellulose fibers, thus enabling processive access of CelD.
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Affiliation(s)
- Fernando Segato
- Department of Microbiology & Molecular Genetics, Oklahoma State University, Stillwater, OK, USA
- Laboratório Nacional de Ciência e Tecnologia do Bioetanol (CTBE), Centro Nacional de Pesquisas em Energia e Materiais, Campinas, Sao Paulo, Brazil
| | - André R L Damasio
- Department of Microbiology & Molecular Genetics, Oklahoma State University, Stillwater, OK, USA
- Department of Biochemistry, Ribeirão Preto School of Medicine, Ribeirão Preto, Sao Paulo, Brazil
| | - Thiago Augusto Gonçalves
- Laboratório Nacional de Ciência e Tecnologia do Bioetanol (CTBE), Centro Nacional de Pesquisas em Energia e Materiais, Campinas, Sao Paulo, Brazil
| | - Mario T Murakami
- Laboratório Nacional de Biociências (LNBio), Campinas, Sao Paulo, Brazil
| | - Fabio M Squina
- Laboratório Nacional de Ciência e Tecnologia do Bioetanol (CTBE), Centro Nacional de Pesquisas em Energia e Materiais, Campinas, Sao Paulo, Brazil
| | | | - Andrew J Mort
- Department of Biochemistry and Molecular Biology, Oklahoma State University, Stillwater, OK, USA
| | - Rolf A Prade
- Department of Microbiology & Molecular Genetics, Oklahoma State University, Stillwater, OK, USA
- Laboratório Nacional de Ciência e Tecnologia do Bioetanol (CTBE), Centro Nacional de Pesquisas em Energia e Materiais, Campinas, Sao Paulo, Brazil
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21
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Fox JM, Levine SE, Blanch HW, Clark DS. An evaluation of cellulose saccharification and fermentation with an engineered Saccharomyces cerevisiae capable of cellobiose and xylose utilization. Biotechnol J 2012; 7:361-73. [DOI: 10.1002/biot.201100209] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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22
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Adav SS, Chao LT, Sze SK. Quantitative secretomic analysis of Trichoderma reesei strains reveals enzymatic composition for lignocellulosic biomass degradation. Mol Cell Proteomics 2012; 11:M111.012419. [PMID: 22355001 DOI: 10.1074/mcp.m111.012419] [Citation(s) in RCA: 111] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Trichoderma reesei is a mesophilic, filamentous fungus, and it is a major industrial source of cellulases, but its lignocellulolytic protein expressions on lignocellulosic biomass are poorly explored at present. The extracellular proteins secreted by T. reesei QM6a wild-type and hypercellulolytic mutant Rut C30 grown on natural lignocellulosic biomasses were explored using a quantitative proteomic approach with 8-plex high throughput isobaric tags for relative and absolute quantification (iTRAQ) and analyzed by liquid chromatography tandem mass spectrometry. We quantified 230 extracellular proteins, including cellulases, hemicellulases, lignin-degrading enzymes, proteases, protein-translocating transporter, and hypothetical proteins. Quantitative iTRAQ results suggested that the expressions and regulations of these lignocellulolytic proteins in the secretome of T. reesei wild-type and mutant Rut C30 were dependent on both nature and complexity of different lignocellulosic carbon sources. Therefore, we discuss here the essential lignocellulolytic proteins for designing an enzyme mixture for optimal lignocellulosic biomass hydrolysis.
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Affiliation(s)
- Sunil S Adav
- School of Biological Sciences, Nanyang Technological University, Singapore
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23
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Cellulolytic Enzyme Production and Enzymatic Hydrolysis for Second-Generation Bioethanol Production. ADVANCES IN BIOCHEMICAL ENGINEERING/BIOTECHNOLOGY 2012; 128:1-24. [DOI: 10.1007/10_2011_131] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
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24
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Hood EE, Devaiah SP, Fake G, Egelkrout E, Teoh KT, Requesens DV, Hayden C, Hood KR, Pappu KM, Carroll J, Howard JA. Manipulating corn germplasm to increase recombinant protein accumulation. PLANT BIOTECHNOLOGY JOURNAL 2012; 10:20-30. [PMID: 21627759 DOI: 10.1111/j.1467-7652.2011.00627.x] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
Using plants as biofactories for industrial enzymes is a developing technology. The application of this technology to plant biomass conversion for biofuels and biobased products has potential for significantly lowering the cost of these products because of lower enzyme production costs. However, the concentration of the enzymes in plant tissue must be high to realize this goal. We describe the enhancement of the accumulation of cellulases in transgenic maize seed as a part of the process to lower the cost of these dominant enzymes for the bioconversion process. We have used breeding to move these genes into elite and high oil germplasm to enhance protein accumulation in grain. We have also explored processing of the grain to isolate the germ, which preferentially contains the enzymes, to further enhance recovery of enzyme on a dry weight basis of raw materials. The enzymes are active on microcrystalline cellulose to release glucose and cellobiose.
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25
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Wang D, Sun J, Yu HL, Li CX, Bao J, Xu JH. Maximum Saccharification of Cellulose Complex by an Enzyme Cocktail Supplemented with Cellulase from Newly Isolated Aspergillus fumigatus ECU0811. Appl Biochem Biotechnol 2011; 166:176-86. [DOI: 10.1007/s12010-011-9414-9] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2011] [Accepted: 10/18/2011] [Indexed: 11/30/2022]
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27
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Liao H, Zhang XZ, Rollin JA, Zhang YHP. A minimal set of bacterial cellulases for consolidated bioprocessing of lignocellulose. Biotechnol J 2011; 6:1409-18. [PMID: 21751395 DOI: 10.1002/biot.201100157] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2011] [Revised: 05/04/2011] [Accepted: 06/06/2011] [Indexed: 11/06/2022]
Abstract
Cost-effective release of fermentable sugars from non-food biomass through biomass pretreatment/enzymatic hydrolysis is still the largest obstacle to second-generation biorefineries. Therefore, the hydrolysis performance of 21 bacterial cellulase mixtures containing the glycoside hydrolase family 5 Bacillus subtilis endoglucanase (BsCel5), family 9 Clostridium phytofermentans processive endoglucanase (CpCel9), and family 48 C. phytofermentans cellobiohydrolase (CpCel48) was studied on partially ordered low-accessibility microcrystalline cellulose (Avicel) and disordered high-accessibility regenerated amorphous cellulose (RAC). Faster hydrolysis rates and higher digestibilities were obtained on RAC than on Avicel. The optimal ratios for maximum cellulose digestibility were dynamic for Avicel but nearly fixed for RAC. Processive endoglucanase CpCel9 was the most important for high cellulose digestibility regardless of substrate type. This study provides important information for the construction of a minimal set of bacterial cellulases for the consolidated bioprocessing bacteria, such as Bacillus subtilis, for converting lignocellulose to biocommodities in a single step.
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Affiliation(s)
- Hehuan Liao
- Biological Systems Engineering Department, Virginia Tech, Blacksburg, VA 24061, USA
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28
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Phillips CM, Iavarone AT, Marletta MA. Quantitative Proteomic Approach for Cellulose Degradation by Neurospora crassa. J Proteome Res 2011; 10:4177-85. [DOI: 10.1021/pr200329b] [Citation(s) in RCA: 88] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Christopher M. Phillips
- Department of Molecular and Cell Biology, University of California, Berkeley, California 94720, United States
| | - Anthony T. Iavarone
- QB3/Chemistry Mass Spectrometry Facility, University of California, Berkeley, California 94720, United States
| | - Michael A. Marletta
- Department of Molecular and Cell Biology, University of California, Berkeley, California 94720, United States
- QB3/Chemistry Mass Spectrometry Facility, University of California, Berkeley, California 94720, United States
- Department of Chemistry, University of California, Berkeley, California 94720, United States
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29
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Levine SE, Fox JM, Clark DS, Blanch HW. A mechanistic model for rational design of optimal cellulase mixtures. Biotechnol Bioeng 2011; 108:2561-70. [DOI: 10.1002/bit.23249] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2011] [Revised: 06/06/2011] [Accepted: 06/20/2011] [Indexed: 11/07/2022]
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30
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Abdel-Rahman MA, Tashiro Y, Sonomoto K. Lactic acid production from lignocellulose-derived sugars using lactic acid bacteria: overview and limits. J Biotechnol 2011; 156:286-301. [PMID: 21729724 DOI: 10.1016/j.jbiotec.2011.06.017] [Citation(s) in RCA: 264] [Impact Index Per Article: 20.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2011] [Revised: 05/31/2011] [Accepted: 06/17/2011] [Indexed: 10/18/2022]
Abstract
Lactic acid is an industrially important product with a large and rapidly expanding market due to its attractive and valuable multi-function properties. The economics of lactic acid production by fermentation is dependent on many factors, of which the cost of the raw materials is very significant. It is very expensive when sugars, e.g., glucose, sucrose, starch, etc., are used as the feedstock for lactic acid production. Therefore, lignocellulosic biomass is a promising feedstock for lactic acid production considering its great availability, sustainability, and low cost compared to refined sugars. Despite these advantages, the commercial use of lignocellulose for lactic acid production is still problematic. This review describes the "conventional" processes for producing lactic acid from lignocellulosic materials with lactic acid bacteria. These processes include: pretreatment of the biomass, enzyme hydrolysis to obtain fermentable sugars, fermentation technologies, and separation and purification of lactic acid. In addition, the difficulties associated with using this biomass for lactic acid production are especially introduced and several key properties that should be targeted for low-cost and advanced fermentation processes are pointed out. We also discuss the metabolism of lignocellulose-derived sugars by lactic acid bacteria.
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Affiliation(s)
- Mohamed Ali Abdel-Rahman
- Laboratory of Microbial Technology, Division of Applied Molecular Microbiology and Biomass Chemistry, Department of Bioscience and Biotechnology, Faculty of Agriculture, Graduate School, Kyushu University, Hakozaki, Higashi-ku, Fukuoka, Japan
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Abstract
Cellulose is an abundant and renewable biopolymer that can be used for biofuel generation; however, structural entrapment with other cell wall components hinders enzyme-substrate interactions, a key bottleneck for ethanol production. Biomass is routinely subjected to treatments that facilitate cellulase-cellulose contacts. Cellulases and glucosidases act by hydrolyzing glycosidic bonds of linear glucose β-1,4-linked polymers, producing glucose. Here we describe eight high-temperature-operating cellulases (TCel enzymes) identified from a survey of thermobacterial and archaeal genomes. Three TCel enzymes preferentially hydrolyzed soluble cellulose, while two preferred insoluble cellulose such as cotton linters and filter paper. TCel enzymes had temperature optima ranging from 85°C to 102°C. TCel enzymes were stable, retaining 80% of initial activity after 120 h at 85°C. Two modes of cellulose breakdown, i.e., with endo- and exo-acting glucanases, were detected, and with two-enzyme combinations at 85°C, synergistic cellulase activity was observed for some enzyme combinations.
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32
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Yan S, Li T, Yao L. Mutational Effects on the Catalytic Mechanism of Cellobiohydrolase I from Trichoderma reesei. J Phys Chem B 2011; 115:4982-9. [DOI: 10.1021/jp200384m] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Affiliation(s)
- Shihai Yan
- Key Lab of Biofuels, Qingdao Institute of Bioenergy
and Bioprocess Technology, Chinese Academy of Sciences, Qingdao 266101, PR China
| | - Tong Li
- Key Lab of Biofuels, Qingdao Institute of Bioenergy
and Bioprocess Technology, Chinese Academy of Sciences, Qingdao 266101, PR China
| | - Lishan Yao
- Key Lab of Biofuels, Qingdao Institute of Bioenergy
and Bioprocess Technology, Chinese Academy of Sciences, Qingdao 266101, PR China
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Szijártó N, Horan E, Zhang J, Puranen T, Siika-aho M, Viikari L. Thermostable endoglucanases in the liquefaction of hydrothermally pretreated wheat straw. BIOTECHNOLOGY FOR BIOFUELS 2011; 4:2. [PMID: 21269447 PMCID: PMC3037870 DOI: 10.1186/1754-6834-4-2] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/27/2010] [Accepted: 01/26/2011] [Indexed: 05/03/2023]
Abstract
BACKGROUND Thermostable enzymes have several benefits in lignocellulose processing. In particular, they potentially allow the use of increased substrate concentrations (because the substrate viscosity decreases as the temperature increases), resulting in improved product yields and reduced capital and processing costs. A short pre-hydrolysis step at an elevated temperature using thermostable enzymes aimed at rapid liquefaction of the feedstock is seen as an attractive way to overcome the technical problems (such as poor mixing and mass transfer properties) connected with high initial solid loadings in the lignocellulose to ethanol process. RESULTS The capability of novel thermostable enzymes to reduce the viscosity of high-solid biomass suspensions using a real-time viscometric measurement method was investigated. Heterologously expressed enzymes from various thermophilic organisms were compared for their ability to liquefy the lignocellulosic substrate, hydrothermally pretreated wheat straw. Once the best enzymes were identified, the optimal temperatures for these enzymes to decrease substrate viscosity were compared. The combined hydrolytic properties of the thermostable preparations were tested in hydrolysis experiments. The studied mixtures were primarily designed to have good liquefaction potential, and therefore contained an enhanced proportion of the key liquefying enzyme, EGII/Cel5A. CONCLUSIONS Endoglucanases were shown to have a superior ability to rapidly reduce the viscosity of the 15% (w/w; dry matter) hydrothermally pretreated wheat straw. Based on temperature profiling studies, Thermoascus aurantiacus EGII/Cel5A was the most promising enzyme for biomass liquefaction. Even though they were not optimized for saccharification, many of the thermostable enzyme mixtures had superior hydrolytic properties compared with the commercial reference enzymes at 55°C.
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Affiliation(s)
- Nóra Szijártó
- University of Helsinki, Department of Food and Environmental Sciences, P.O. Box 27, FIN-00014, Helsinki, Finland
| | - Emma Horan
- University of Helsinki, Department of Food and Environmental Sciences, P.O. Box 27, FIN-00014, Helsinki, Finland
| | - Junhua Zhang
- University of Helsinki, Department of Food and Environmental Sciences, P.O. Box 27, FIN-00014, Helsinki, Finland
| | - Terhi Puranen
- Roal Oy, Tykkimäentie 15, FIN-05200, Rajamäki, Finland
| | - Matti Siika-aho
- VTT Technical Research Centre of Finland, PO Box 1000, FIN-02044, Espoo, Finland
| | - Liisa Viikari
- University of Helsinki, Department of Food and Environmental Sciences, P.O. Box 27, FIN-00014, Helsinki, Finland
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34
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Szijártó N, Siika-aho M, Sontag-Strohm T, Viikari L. Liquefaction of hydrothermally pretreated wheat straw at high-solids content by purified Trichoderma enzymes. BIORESOURCE TECHNOLOGY 2011; 102:1968-74. [PMID: 20884202 DOI: 10.1016/j.biortech.2010.09.012] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/19/2010] [Revised: 09/03/2010] [Accepted: 09/03/2010] [Indexed: 05/03/2023]
Abstract
Enzymatic liquefaction was studied by measuring continuously the flowability change of high-solids lignocellulose substrates using a real time viscometric method. Hydrolysis experiments of hydrothermally pretreated wheat straw were carried out with purified enzymes from Trichoderma reesei; Cel7A, Cel6A, Cel7B, Cel5A, Cel12A and Xyn11A. Results obtained at 15% (w/w) solids revealed that endoglucanases, in particular Cel5A, are the key enzymes to rapidly reduce the viscosity of lignocellulose substrate. Cellobiohydrolases had only minor and the xylanase practically no effect on the viscosity. Efficient, fast liquefaction was obtained already at a dosage of 1.5 mg of Cel5A/gdrysolids. Partial replacement or supplementation of Cel5A by the other major hydrolytic enzymes did not improve the liquefaction. The reduction of viscosity did not correlate with the saccharification obtained in the same reaction, suggesting that efficient liquefaction is rather dependent on the site than the frequency of enzymatic cleavages.
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Affiliation(s)
- Nóra Szijártó
- University of Helsinki, Department of Food and Environmental Sciences, P.O. Box 27, FIN-00014 Helsinki, Finland.
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35
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Throndset W, Kim S, Bower B, Lantz S, Kelemen B, Pepsin M, Chow N, Mitchinson C, Ward M. Flow cytometric sorting of the filamentous fungus Trichoderma reesei for improved strains. Enzyme Microb Technol 2010. [DOI: 10.1016/j.enzmictec.2010.09.003] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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36
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Hydrolytic Enzyme of Cellulose for Complex Formulation Applied Research. Appl Biochem Biotechnol 2010; 164:23-33. [DOI: 10.1007/s12010-010-9111-0] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2010] [Accepted: 10/11/2010] [Indexed: 11/26/2022]
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37
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Jimenez-Flores R, Fake G, Carroll J, Hood E, Howard J. A novel method for evaluating the release of fermentable sugars from cellulosic biomass. Enzyme Microb Technol 2010. [DOI: 10.1016/j.enzmictec.2010.07.003] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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38
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Lantz SE, Goedegebuur F, Hommes R, Kaper T, Kelemen BR, Mitchinson C, Wallace L, Ståhlberg J, Larenas EA. Hypocrea jecorina CEL6A protein engineering. BIOTECHNOLOGY FOR BIOFUELS 2010; 3:20. [PMID: 20822549 PMCID: PMC2945327 DOI: 10.1186/1754-6834-3-20] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/15/2010] [Accepted: 09/08/2010] [Indexed: 05/03/2023]
Abstract
The complex technology of converting lignocellulose to fuels such as ethanol has advanced rapidly over the past few years, and enzymes are a critical component of this technology. The production of effective enzyme systems at cost structures that facilitate commercial processes has been the focus of research for many years. Towards this end, the H. jecorina cellobiohydrolases, CEL7A and CEL6A, have been the subject of protein engineering at Genencor. Our first rounds of cellobiohydrolase engineering were directed towards improving the thermostability of both of these enzymes and produced variants of CEL7A and CEL6A with apparent melting temperatures above 70°C, placing their stability on par with that of H. jecorina CEL5A (EG2) and CEL3A (BGL1). We have now moved towards improving CEL6A- and CEL7A-specific performance in the context of a complete enzyme system under industrially relevant conditions. Achievement of these goals required development of new screening strategies and tools. We discuss these advances along with some results, focusing mainly on engineering of CEL6A.
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Affiliation(s)
- Suzanne E Lantz
- Genencor Division, Danisco USA Inc., 925 Page Mill Rd. Palo Alto, CA 94304, USA
| | - Frits Goedegebuur
- Genencor, a Danisco Division, Archimedesweg 30, 2333CN, Leiden, The Netherlands
| | - Ronald Hommes
- Genencor, a Danisco Division, Archimedesweg 30, 2333CN, Leiden, The Netherlands
| | - Thijs Kaper
- Genencor Division, Danisco USA Inc., 925 Page Mill Rd. Palo Alto, CA 94304, USA
| | - Bradley R Kelemen
- Genencor Division, Danisco USA Inc., 925 Page Mill Rd. Palo Alto, CA 94304, USA
| | - Colin Mitchinson
- Genencor Division, Danisco USA Inc., 925 Page Mill Rd. Palo Alto, CA 94304, USA
| | - Louise Wallace
- Genencor Division, Danisco USA Inc., 925 Page Mill Rd. Palo Alto, CA 94304, USA
| | - Jerry Ståhlberg
- Department of Molecular Biology, Swedish University of Agricultural Sciences, POB 590, SE-751 24 Uppsala, Sweden
| | - Edmundo A Larenas
- Genencor Division, Danisco USA Inc., 925 Page Mill Rd. Palo Alto, CA 94304, USA
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Murphy L, Baumann MJ, Borch K, Sweeney M, Westh P. An enzymatic signal amplification system for calorimetric studies of cellobiohydrolases. Anal Biochem 2010; 404:140-8. [DOI: 10.1016/j.ab.2010.04.020] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2010] [Revised: 04/14/2010] [Accepted: 04/18/2010] [Indexed: 10/19/2022]
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40
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Zhou W, Xu Y, Schüttler HB. Cellulose hydrolysis in evolving substrate morphologies III: Time-scale analysis. Biotechnol Bioeng 2010; 107:224-34. [DOI: 10.1002/bit.22814] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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41
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Banerjee G, Car S, Scott-Craig JS, Borrusch MS, Aslam N, Walton JD. Synthetic enzyme mixtures for biomass deconstruction: Production and optimization of a core set. Biotechnol Bioeng 2010; 106:707-20. [DOI: 10.1002/bit.22741] [Citation(s) in RCA: 93] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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42
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Bu L, Beckham GT, Crowley MF, Chang CH, Matthews JF, Bomble YJ, Adney WS, Himmel ME, Nimlos MR. The energy landscape for the interaction of the family 1 carbohydrate-binding module and the cellulose surface is altered by hydrolyzed glycosidic bonds. J Phys Chem B 2009; 113:10994-1002. [PMID: 19594145 DOI: 10.1021/jp904003z] [Citation(s) in RCA: 66] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
A multiscale simulation model is used to construct potential and free energy surfaces for the carbohydrate-binding module [CBM] from an industrially important cellulase, Trichoderma reesei cellobiohydrolase I, on the hydrophobic face of a coarse-grained cellulose Ibeta polymorph. We predict from computation that the CBM alone exhibits regions of stability on the hydrophobic face of cellulose every 5 and 10 A, corresponding to a glucose unit and a cellobiose unit, respectively. In addition, we predict a new role for the CBM: specifically, that in the presence of hydrolyzed cellulose chain ends, the CBM exerts a thermodynamic driving force to translate away from the free cellulose chain ends. This suggests that the CBM is not only required for binding to cellulose, as has been known for two decades, but also that it has evolved to both assist the enzyme in recognizing a cellulose chain end and exert a driving force on the enzyme during processive hydrolysis of cellulose.
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Affiliation(s)
- Lintao Bu
- National Bioenergy Center, National Renewable Energy Laboratory, Golden, Colorado 80401, USA
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43
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Meyer AS, Rosgaard L, Sørensen HR. The minimal enzyme cocktail concept for biomass processing. J Cereal Sci 2009. [DOI: 10.1016/j.jcs.2009.01.010] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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44
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Zhou J, Wang YH, Chu J, Luo LZ, Zhuang YP, Zhang SL. Optimization of cellulase mixture for efficient hydrolysis of steam-exploded corn stover by statistically designed experiments. BIORESOURCE TECHNOLOGY 2009; 100:819-25. [PMID: 18771915 DOI: 10.1016/j.biortech.2008.06.068] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/07/2008] [Revised: 06/24/2008] [Accepted: 06/24/2008] [Indexed: 05/10/2023]
Abstract
To improve the enzymatic hydrolytic efficiency and reduce production cost, a statistically designed experimental approach was used to optimize the composition of cellulase mixture so as to maximize the amount of glucose produced from steam-exploded corn stover (SECS). Using seven purified enzymes (cellobiohydrolases, Cel7A, Cel6A, Cel6B; endoglucanases, Cel7B, Cel12A, Cel61A; and beta-glucosidase) from Trichoderma viride T 100-14 mutant strain, a multi-enzyme mixture was constituted after screening and optimization. The final optimal composition (mol%) of the multi-enzyme mixture was Cel7A (19.8%), Cel6A (37.5%), Cel6B (4.7%), Cel7B (17.7%), Cel12A (15.2%), Cel61A (2.3%) and beta-glucosidase (2.8%). The subsequent verification experiments followed by glucose assay together with scanning electron microscopy (SEM) observation confirmed the validity of the models. The multi-enzyme mixture displayed a high performance in converting the cellulosic substrate (SECS). The amount of glucose produced (15.5mg/ml) was 2.1 times as that of the crude cellulase preparation. The results indicated that the optimized cellulase mixture is an available and efficient paradigm for the hydrolysis of lignocellulosic substrate. The enhanced cellulolytic activity displayed by the constructed cellulase mixture could be used as an effective tool for producing bioethanol efficiently from cellulose.
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Affiliation(s)
- Jin Zhou
- State Key Laboratory of Bioreactor Engineering, National Engineering Research Center for Biotechnology (Shanghai), East China University of Science and Technology, 130 Meilong Road, Shanghai 200237, PR China
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45
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Hood EE, Love R, Lane J, Bray J, Clough R, Pappu K, Drees C, Hood KR, Yoon S, Ahmad A, Howard JA. Subcellular targeting is a key condition for high-level accumulation of cellulase protein in transgenic maize seed. PLANT BIOTECHNOLOGY JOURNAL 2007; 5:709-19. [PMID: 17614952 DOI: 10.1111/j.1467-7652.2007.00275.x] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
Ethanol from lignocellulosic biomass is being pursued as an alternative to petroleum-based transportation fuels. To succeed in this endeavour, efficient digestion of cellulose into monomeric sugar streams is a key step. Current production systems for cellulase enzymes, i.e. fungi and bacteria, cannot meet the cost and huge volume requirements of this commodity-based industry. Transgenic maize (Zea mays L.) seed containing cellulase protein in embryo tissue, with protein localized to the endoplasmic reticulum, cell wall or vacuole, allows the recovery of commercial amounts of enzyme. E1 cellulase, an endo-beta-1,4-glucanase from Acidothermus cellulolyticus, was recovered at levels greater than 16% total soluble protein (TSP) in single seed. More significantly, cellobiohydrolase I (CBH I), an exocellulase from Trichoderma reesei, also accumulated to levels greater than 16% TSP in single seed, nearly 1000-fold higher than the expression in any other plant reported in the literature. The catalytic domain was the dominant form of E1 that was detected in the endoplasmic reticulum and vacuole, whereas CBH I holoenzyme was present in the cell wall. With one exception, individual transgenic events contained single inserts. Recovery of high levels of enzyme in T2 ears demonstrated that expression is likely to be stable over multiple generations. The enzymes were active in cleaving soluble substrate.
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Affiliation(s)
- Elizabeth E Hood
- Arkansas State University, PO Box 2760, State University, AR 72467, USA.
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46
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Jeoh T, Ishizawa CI, Davis MF, Himmel ME, Adney WS, Johnson DK. Cellulase digestibility of pretreated biomass is limited by cellulose accessibility. Biotechnol Bioeng 2007; 98:112-22. [PMID: 17335064 DOI: 10.1002/bit.21408] [Citation(s) in RCA: 251] [Impact Index Per Article: 14.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Attempts to correlate the physical and chemical properties of biomass to its susceptibility to enzyme digestion are often inconclusive or contradictory depending on variables such as the type of substrate, the pretreatment conditions and measurement techniques. In this study, we present a direct method for measuring the key factors governing cellulose digestibility in a biomass sample by directly probing cellulase binding and activity using a purified cellobiohydrolase (Cel7A) from Trichoderma reesei. Fluorescence-labeled T. reesei Cel7A was used to assay pretreated corn stover samples and pure cellulosic substrates to identify barriers to accessibility by this important component of cellulase preparations. The results showed cellulose conversion improved when T. reesei Cel7A bound in higher concentrations, indicating that the enzyme had greater access to the substrate. Factors such as the pretreatment severity, drying after pretreatment, and cellulose crystallinity were found to directly impact enzyme accessibility. This study provides direct evidence to support the notion that the best pretreatment schemes for rendering biomass more digestible to cellobiohydrolase enzymes are those that improve access to the cellulose in biomass cell walls, as well as those able to reduce the crystallinity of cell wall cellulose.
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Affiliation(s)
- Tina Jeoh
- Chemical and Biosciences Center, National Renewable Energy Laboratory, 1617 Cole Blvd., Golden, Colorado 80401, USA
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47
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Percival Zhang YH, Himmel ME, Mielenz JR. Outlook for cellulase improvement: screening and selection strategies. Biotechnol Adv 2006; 24:452-81. [PMID: 16690241 DOI: 10.1016/j.biotechadv.2006.03.003] [Citation(s) in RCA: 663] [Impact Index Per Article: 36.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2006] [Revised: 03/06/2006] [Accepted: 03/11/2006] [Indexed: 10/24/2022]
Abstract
Cellulose is the most abundant renewable natural biological resource, and the production of biobased products and bioenergy from less costly renewable lignocellulosic materials is important for the sustainable development of human beings. A reduction in cellulase production cost, an improvement in cellulase performance, and an increase in sugar yields are all vital to reduce the processing costs of biorefineries. Improvements in specific cellulase activities for non-complexed cellulase mixtures can be implemented through cellulase engineering based on rational design or directed evolution for each cellulase component enzyme, as well as on the reconstitution of cellulase components. Here, we review quantitative cellulase activity assays using soluble and insoluble substrates, and focus on their advantages and limitations. Because there are no clear relationships between cellulase activities on soluble substrates and those on insoluble substrates, soluble substrates should not be used to screen or select improved cellulases for processing relevant solid substrates, such as plant cell walls. Cellulase improvement strategies based on directed evolution using screening on soluble substrates have been only moderately successful, and have primarily targeted improvement in thermal tolerance. Heterogeneity of insoluble cellulose, unclear dynamic interactions between insoluble substrate and cellulase components, and the complex competitive and/or synergic relationship among cellulase components limit rational design and/or strategies, depending on activity screening approaches. Herein, we hypothesize that continuous culture using insoluble cellulosic substrates could be a powerful selection tool for enriching beneficial cellulase mutants from the large library displayed on the cell surface.
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Affiliation(s)
- Y-H Percival Zhang
- Biological Systems Engineering Department, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061, USA.
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48
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Pu Y, Ziemer C, Ragauskas AJ. CP/MAS 13C NMR analysis of cellulase treated bleached softwood kraft pulp. Carbohydr Res 2006; 341:591-7. [PMID: 16442511 DOI: 10.1016/j.carres.2005.12.012] [Citation(s) in RCA: 82] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2005] [Revised: 12/16/2005] [Accepted: 12/29/2005] [Indexed: 11/18/2022]
Abstract
Fully bleached softwood kraft pulps were hydrolyzed with cellulase (1,4-(1,3:1,4)-beta-D-glucan 4-glucano-hydrolase, EC 3.2.1.4) from Trichoderma reesei. Supra-molecular structural features of cellulose during enzymatic hydrolysis were examined by using CP/MAS 13C NMR spectra in combination with line-fitting analysis. Different types of cellulose allomorphs (cellulose I(alpha), cellulose I(beta), para-crystalline) and amorphous regions were hydrolyzed to a different extent by the enzyme used. Also observed was a rapid initial phase for hydrolysis of regions followed by a slow hydrolysis phase. Cellulose I(alpha), para-crystalline, and non-crystalline regions of cellulose are more susceptible to enzymatic hydrolysis than cellulose I(beta) during the initial phase. After the initial phase, all the regions are then similarly susceptible to enzymatic hydrolysis.
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Affiliation(s)
- Yunqiao Pu
- Institute of Paper Science and Technology, Georgia Institute of Technology, 500 10th St., Atlanta, GA 30332, USA
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49
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Zhang YHP, Lynd LR. A functionally based model for hydrolysis of cellulose by fungal cellulase. Biotechnol Bioeng 2006; 94:888-98. [PMID: 16685742 DOI: 10.1002/bit.20906] [Citation(s) in RCA: 124] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
A new functionally based kinetic model for enzymatic hydrolysis of pure cellulose by the Trichoderma cellulase system is presented. The model represents the actions of cellobiohydrolases I, cellobiohydrolase II, and endoglucanase I; and incorporates two measurable and physically interpretable substrate parameters: the degree of polymerization (DP) and the fraction of beta-glucosidic bonds accessible to cellulase, F(a) (Zhang and Lynd, 2004). Initial enzyme-limited reaction rates simulated by the model are consistent with several important behaviors reported in the literature, including the effects of substrate characteristics on exoglucanase and endoglucanase activities; the degree of endo/exoglucanase synergy; the endoglucanase partition coefficient on hydrolysis rates; and enzyme loading on relative reaction rates for different substrates. This is the first cellulase kinetic model involving a single set of kinetic parameters that is successfully applied to a variety of cellulosic substrates, and the first that describes more than one behavior associated with enzymatic hydrolysis. The model has potential utility for data accommodation and design of industrial processes, structuring, testing, and extending understanding of cellulase enzyme systems when experimental date are available, and providing guidance for functional design of cellulase systems at a molecular scale. Opportunities to further refine cellulase kinetic models are discussed, including parameters that would benefit from further study.
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Affiliation(s)
- Y-H Percival Zhang
- Biological Systems Engineering Department, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061, USA.
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50
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Recovery of biological activity in reversibly inactivated proteins by three phase partitioning. Enzyme Microb Technol 2005. [DOI: 10.1016/j.enzmictec.2005.02.007] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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