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Tang C, Gandla ML, Jönsson LJ. LPMO-supported saccharification of biomass: effects of continuous aeration of reaction mixtures with variable fractions of water-insoluble solids and cellulolytic enzymes. BIOTECHNOLOGY FOR BIOFUELS AND BIOPRODUCTS 2023; 16:156. [PMID: 37865768 PMCID: PMC10590502 DOI: 10.1186/s13068-023-02407-y] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/17/2023] [Accepted: 10/10/2023] [Indexed: 10/23/2023]
Abstract
BACKGROUND High substrate concentrations and high sugar yields are important aspects of enzymatic saccharification of lignocellulosic substrates. The benefit of supporting the catalytic action of lytic polysaccharide monooxygenase (LPMO) through continuous aeration of slurries of pretreated softwood was weighed against problems associated with increasing substrate content (quantitated as WIS, water-insoluble solids, in the range 12.5-17.5%), and was compared to the beneficial effect on the saccharification reaction achieved by increasing the enzyme preparation (Cellic CTec3) loadings. Aerated reactions were compared to reactions supplied with N2 to assess the contribution of LPMO to the saccharification reactions. Analysis using 13C NMR spectroscopy, XRD, Simons' staining, BET analysis, and SEM analysis was used to gain further insights into the effects of the cellulolytic enzymes on the substrate under different reaction conditions. RESULTS Although glucose production after 72 h was higher at 17.5% WIS than at 12.5% WIS, glucan conversion decreased with 24% (air) and 17% (N2). Compared to reactions with N2, the average increases in glucose production for aerated reactions were 91% (12.5% WIS), 70% (15.0% WIS), and 67% (17.5% WIS). Improvements in glucan conversion through aeration were larger (55-86%) than the negative effects of increasing WIS content. For reactions with 12.5% WIS, increased enzyme dosage with 50% improved glucan conversion with 25-30% for air and N2, whereas improvements with double enzyme dosage were 30% (N2) and 39% (air). Structural analyses of the solid fractions revealed that the enzymatic reaction, particularly with aeration, created increased surface area (BET analysis), increased disorder (SEM analysis), decreased crystallinity (XRD), and increased dye adsorption based on the cellulose content (Simons' staining). CONCLUSIONS The gains in glucan conversion with aeration were larger than the decreases observed due to increased substrate content, resulting in higher glucan conversion when using aeration at the highest WIS value than when using N2 at the lowest WIS value. The increase in glucan conversion with double enzyme preparation dosage was smaller than the increase achieved with aeration. The results demonstrate the potential in using proper aeration to exploit the inherent capacity of LPMO in enzymatic saccharification of lignocellulosic substrates and provide detailed information about the characteristics of the substrate after interaction with cellulolytic enzymes.
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Affiliation(s)
- Chaojun Tang
- Department of Chemistry, Umeå University, 901 87, Umeå, Sweden
| | | | - Leif J Jönsson
- Department of Chemistry, Umeå University, 901 87, Umeå, Sweden.
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Pan N, Jiang B, Hu J, Huang M, He J, Jiang Q, Zhao L, Shen F, Tian D. The coupling effects between acid-catalyzed hydrothermal pretreatment and acidic/alkaline deep eutectic solvent extraction for wheat straw fractionation. BIORESOURCE TECHNOLOGY 2023; 386:129579. [PMID: 37506939 DOI: 10.1016/j.biortech.2023.129579] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/07/2023] [Revised: 07/19/2023] [Accepted: 07/25/2023] [Indexed: 07/30/2023]
Abstract
Mild hydrothermal pretreatment (HP) integrating with solvent extraction is a promising two-step technique to enhance the overall lignin and carbohydrate output for lignocellulose fractionation. This work comparatively assessed the coupling effect between mild HP (the first step) and the emerging acidic choline chloride-natural acid or alkaline choline hydroxide based deep eutectic solvents (DES, the second step) for wheat straw fractionation. It was shown HP with 0.3% p-toluenesulfonic acid (p-TsOH) catalyst achieved a good compromise between complete hemicellulose removal (nearly 100%) and high cellulose recovery (99.2%). While choline hydroxide based DES showed better coupling effect with HP than choline chloride-natural acid DES, corresponding to 75.6 and 31.2% lignin removal respectively. It was proposed that the alkaline DES enhanced lignocellulose swelling the lignin phenolic hydroxyl groups deprotonation and thus facilitating lignin solubilization despite of its condensation at HP. Therefore, the alkaline DES resulting cellulose-rich fraction exhibited higher potential for further processing.
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Affiliation(s)
- Na Pan
- College of Environmental Sciences, Sichuan Agricultural University, Chengdu, Sichuan 611130, PR China
| | - Baiheng Jiang
- College of Environmental Sciences, Sichuan Agricultural University, Chengdu, Sichuan 611130, PR China
| | - Jinguang Hu
- Department of Chemical and Petroleum Engineering, University of Calgary, 2500 University Dr. NW, Calgary, AB T2N 1N4, Canada
| | - Mei Huang
- College of Environmental Sciences, Sichuan Agricultural University, Chengdu, Sichuan 611130, PR China
| | - Jinsong He
- College of Environmental Sciences, Sichuan Agricultural University, Chengdu, Sichuan 611130, PR China
| | - Qin Jiang
- College of Environmental Sciences, Sichuan Agricultural University, Chengdu, Sichuan 611130, PR China
| | - Li Zhao
- College of Environmental Sciences, Sichuan Agricultural University, Chengdu, Sichuan 611130, PR China
| | - Fei Shen
- College of Environmental Sciences, Sichuan Agricultural University, Chengdu, Sichuan 611130, PR China
| | - Dong Tian
- College of Environmental Sciences, Sichuan Agricultural University, Chengdu, Sichuan 611130, PR China.
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Wu J, Dong Y, Zhang H, Liu J, Renneckar S, Saddler J. Reduced cellulose accessibility slows down enzyme-mediated hydrolysis of cellulose. BIORESOURCE TECHNOLOGY 2023; 371:128647. [PMID: 36681353 DOI: 10.1016/j.biortech.2023.128647] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/21/2022] [Revised: 01/13/2023] [Accepted: 01/16/2023] [Indexed: 06/17/2023]
Abstract
Enzyme-mediated hydrolysis of cellulose always starts with an initial rapid phase, which gradually slows down, sometimes resulting in incomplete cellulose hydrolysis even after prolonged incubation. Although mechanisms such as end-product inhibition are known to play a role, the predominant mechanism appears to be reduced cellulose accessibility to the enzymes. When using Simon's stain to quantify accessibility, the accessibility of mechanically disintegrated and phosphoric acid-swollen cellulose substrates decreased as hydrolysis proceeded. In contrast, the poor initial accessibility of Avicel remained low throughout hydrolysis. However, washing the residual cellulose increased cellulose accessibility, likely due to the removal of tightly bound but non-productive enzymes which blocked access to more active enzymes in solution. Atomic force microscopy (AFM) analysis of the initial and residual cellulose collected when the hydrolysis plateaued, showed an increase in the roughness of the cellulose surface, possibly resulting in the tighter binding of less active cellulases.
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Affiliation(s)
- Jie Wu
- Forest Product Biotechnology/Bioenergy Group, Department of Wood Science, Faculty of Forestry, University of British Columbia, 2424 Main Mall, Vancouver, British Columbia V6T 1Z4, Canada
| | - Yintian Dong
- Forest Product Biotechnology/Bioenergy Group, Department of Wood Science, Faculty of Forestry, University of British Columbia, 2424 Main Mall, Vancouver, British Columbia V6T 1Z4, Canada
| | - Huaiyu Zhang
- Advanced Renewable Materials Lab, Department of Wood Science, Faculty of Forestry, University of British Columbia, 2424 Main Mall, Vancouver, British Columbia V6T 1Z4, Canada
| | - Jingyun Liu
- Forest Product Biotechnology/Bioenergy Group, Department of Wood Science, Faculty of Forestry, University of British Columbia, 2424 Main Mall, Vancouver, British Columbia V6T 1Z4, Canada; School of Chemical Engineering, Sichuan University, Chengdu 610065, China
| | - Scott Renneckar
- Advanced Renewable Materials Lab, Department of Wood Science, Faculty of Forestry, University of British Columbia, 2424 Main Mall, Vancouver, British Columbia V6T 1Z4, Canada
| | - Jack Saddler
- Forest Product Biotechnology/Bioenergy Group, Department of Wood Science, Faculty of Forestry, University of British Columbia, 2424 Main Mall, Vancouver, British Columbia V6T 1Z4, Canada.
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Wang Y, Meng X, Tian Y, Kim KH, Jia L, Pu Y, Leem G, Kumar D, Eudes A, Ragauskas AJ, Yoo CG. Engineered Sorghum Bagasse Enables a Sustainable Biorefinery with p-Hydroxybenzoic Acid-Based Deep Eutectic Solvent. CHEMSUSCHEM 2021; 14:5235-5244. [PMID: 34533890 DOI: 10.1002/cssc.202101492] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/14/2021] [Revised: 09/09/2021] [Indexed: 06/13/2023]
Abstract
Integrating multidisciplinary research in plant genetic engineering and renewable deep eutectic solvents (DESs) can facilitate a sustainable and economic biorefinery. Herein, we leveraged a plant genetic engineering approach to specifically incorporate C6 C1 monomers into the lignin structure. By expressing the bacterial ubiC gene in sorghum, p-hydroxybenzoic acid (PB)-rich lignin was incorporated into the plant cell wall while this monomer was completely absent in the lignin of the wild-type (WT) biomass. A DES was synthesized with choline chloride (ChCl) and PB and applied to the pretreatment of the PB-rich mutant biomass for a sustainable biorefinery. The release of fermentable sugars was significantly enhanced (∼190 % increase) compared to untreated biomass by the DES pretreatment. In particular, the glucose released from the pretreated mutant biomass was up to 12 % higher than that from the pretreated WT biomass. Lignin was effectively removed from the biomass with the preservation of more than half of the β-Ο-4 linkages without condensed aromatic structures. Hydrogenolysis of the fractionated lignin was conducted to demonstrate the potential of phenolic compound production. In addition, a simple hydrothermal treatment could selectively extract PB from the same engineered lignin, showing a possible circular biorefinery. These results suggest that the combination of PB-based DES and engineered PB-rich biomass is a promising strategy to achieve a sustainable closed-loop biorefinery.
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Affiliation(s)
- Yunxuan Wang
- Department of Chemical Engineering, College of Environmental Science and Forestry, State University of New York, Syracuse, NY 13210, USA
| | - Xianzhi Meng
- Department of Chemical & Biomolecular Engineering, University of Tennessee-Knoxville, Knoxville, TN 37996, USA
| | - Yang Tian
- Environmental Genomics and Systems Biology Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA
- Joint BioEnergy Institute, Emeryville, CA 94608, USA
| | - Kwang Ho Kim
- Clean Energy Research Center, Korea Institute of Science and Technology, Seoul, 02797, South Korea
- Department of Wood Science, University of British Columbia, Vancouver, BC V6T 1Z4, Canada
| | - Linjing Jia
- Department of Chemical Engineering, College of Environmental Science and Forestry, State University of New York, Syracuse, NY 13210, USA
| | - Yunqiao Pu
- Center of Bioenergy Innovation, Biosciences Division, University of Tennessee-Oak Ridge National Laboratory Joint Institute for Biological Science Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA
| | - Gyu Leem
- Department of Chemistry, College of Environmental Science and Forestry, State University of New York, Syracuse, NY 13210, USA
- The Michael M. Szwarc Polymer Research Institute, Syracuse, NY 13210, USA
| | - Deepak Kumar
- Department of Chemical Engineering, College of Environmental Science and Forestry, State University of New York, Syracuse, NY 13210, USA
| | - Aymerick Eudes
- Environmental Genomics and Systems Biology Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA
- Joint BioEnergy Institute, Emeryville, CA 94608, USA
| | - Arthur J Ragauskas
- Department of Chemical & Biomolecular Engineering, University of Tennessee-Knoxville, Knoxville, TN 37996, USA
- Center of Bioenergy Innovation, Biosciences Division, University of Tennessee-Oak Ridge National Laboratory Joint Institute for Biological Science Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA
- Center of Renewable Carbon, Department of Forestry, Wildlife, and Fisheries, University of Tennessee Institute of Agriculture, Knoxville, TN 37996, USA
| | - Chang Geun Yoo
- Department of Chemical Engineering, College of Environmental Science and Forestry, State University of New York, Syracuse, NY 13210, USA
- The Michael M. Szwarc Polymer Research Institute, Syracuse, NY 13210, USA
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Bi R, Khatri V, Chandra R, Takada M, Figueroa DV, Zhou H, Wu J, Charron D, Saddler J. Enhancing Kraft based dissolving pulp production by integrating green liquor neutralization. CARBOHYDRATE POLYMER TECHNOLOGIES AND APPLICATIONS 2021. [DOI: 10.1016/j.carpta.2021.100034] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
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de Freitas EN, Alnoch RC, Contato AG, Nogueira KMV, Crevelin EJ, de Moraes LAB, Silva RN, Martínez CA, Polizeli MDLTM. Enzymatic Pretreatment with Laccases from Lentinus sajor-caju Induces Structural Modification in Lignin and Enhances the Digestibility of Tropical Forage Grass ( Panicum maximum) Grown under Future Climate Conditions. Int J Mol Sci 2021; 22:ijms22179445. [PMID: 34502353 PMCID: PMC8431176 DOI: 10.3390/ijms22179445] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2021] [Revised: 08/22/2021] [Accepted: 08/24/2021] [Indexed: 01/25/2023] Open
Abstract
Since laccase acts specifically in lignin, the major contributor to biomass recalcitrance, this biocatalyst represents an important alternative to the pretreatment of lignocellulosic biomass. Therefore, this study investigates the laccase pretreatment and climate change effects on the hydrolytic performance of Panicum maximum. Through a Trop-T-FACE system, P. maximum grew under current (Control (C)) and future climate conditions: elevated temperature (2 °C more than the ambient canopy temperature) combined with elevated atmospheric CO2 concentration(600 μmol mol−1), name as eT+eC. Pretreatment using a laccase-rich crude extract from Lentinus sajor caju was optimized through statistical strategies, resulting in an increase in the sugar yield of P. maximum biomass (up to 57%) comparing to non-treated biomass and enabling hydrolysis at higher solid loading, achieving up to 26 g L−1. These increments are related to lignin removal (up to 46%) and lignin hydrophilization catalyzed by laccase. Results from SEM, CLSM, FTIR, and GC-MS supported the laccase-catalyzed lignin removal. Moreover, laccase mitigates climate effects, and no significant differences in hydrolytic potential were found between C and eT+eC groups. This study shows that crude laccase pretreatment is a potential and sustainable method for biorefinery solutions and helped establish P. maximum as a promising energy crop.
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Affiliation(s)
- Emanuelle Neiverth de Freitas
- Departamento de Bioquímica e Imunologia, Faculdade de Medicina de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto 14049-900, Brazil; (E.N.d.F.); (A.G.C.); (K.M.V.N.); (R.N.S.)
| | - Robson Carlos Alnoch
- Departamento de Biologia, Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto 14050-901, Brazil; (R.C.A.); (C.A.M.)
| | - Alex Graça Contato
- Departamento de Bioquímica e Imunologia, Faculdade de Medicina de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto 14049-900, Brazil; (E.N.d.F.); (A.G.C.); (K.M.V.N.); (R.N.S.)
| | - Karoline Maria V. Nogueira
- Departamento de Bioquímica e Imunologia, Faculdade de Medicina de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto 14049-900, Brazil; (E.N.d.F.); (A.G.C.); (K.M.V.N.); (R.N.S.)
| | - Eduardo José Crevelin
- Departamento de Química, Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto 14050-901, Brazil; (E.J.C.); (L.A.B.d.M.)
| | - Luiz Alberto Beraldo de Moraes
- Departamento de Química, Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto 14050-901, Brazil; (E.J.C.); (L.A.B.d.M.)
| | - Roberto Nascimento Silva
- Departamento de Bioquímica e Imunologia, Faculdade de Medicina de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto 14049-900, Brazil; (E.N.d.F.); (A.G.C.); (K.M.V.N.); (R.N.S.)
| | - Carlos Alberto Martínez
- Departamento de Biologia, Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto 14050-901, Brazil; (R.C.A.); (C.A.M.)
| | - Maria de Lourdes T. M. Polizeli
- Departamento de Bioquímica e Imunologia, Faculdade de Medicina de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto 14049-900, Brazil; (E.N.d.F.); (A.G.C.); (K.M.V.N.); (R.N.S.)
- Departamento de Biologia, Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto 14050-901, Brazil; (R.C.A.); (C.A.M.)
- Correspondence:
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Leroy A, Falourd X, Foucat L, Méchin V, Guillon F, Paës G. Evaluating polymer interplay after hot water pretreatment to investigate maize stem internode recalcitrance. BIOTECHNOLOGY FOR BIOFUELS 2021; 14:164. [PMID: 34332625 PMCID: PMC8325808 DOI: 10.1186/s13068-021-02015-8] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/21/2021] [Accepted: 07/21/2021] [Indexed: 05/12/2023]
Abstract
BACKGROUND Biomass recalcitrance is governed by various molecular and structural factors but the interplay between these multiscale factors remains unclear. In this study, hot water pretreatment (HWP) was applied to maize stem internodes to highlight the impact of the ultrastructure of the polymers and their interactions on the accessibility and recalcitrance of the lignocellulosic biomass. The impact of HWP was analysed at different scales, from the polymer ultrastructure or water mobility to the cell wall organisation by combining complementary compositional, spectral and NMR analyses. RESULTS HWP increased the kinetics and yield of saccharification. Chemical characterisation showed that HWP altered cell wall composition with a loss of hemicelluloses (up to 45% in the 40-min HWP) and of ferulic acid cross-linking associated with lignin enrichment. The lignin structure was also altered (up to 35% reduction in β-O-4 bonds), associated with slight depolymerisation/repolymerisation depending on the length of treatment. The increase in [Formula: see text], [Formula: see text] and specific surface area (SSA) showed that the cellulose environment was looser after pretreatment. These changes were linked to the increased accessibility of more constrained water to the cellulose in the 5-15 nm pore size range. CONCLUSION The loss of hemicelluloses and changes in polymer structural features caused by HWP led to reorganisation of the lignocellulose matrix. These modifications increased the SSA and redistributed the water thereby increasing the accessibility of cellulases and enhancing hydrolysis. Interestingly, lignin content did not have a negative impact on enzymatic hydrolysis but a higher lignin condensed state appeared to promote saccharification. The environment and organisation of lignin is thus more important than its concentration in explaining cellulose accessibility. Elucidating the interactions between polymers is the key to understanding LB recalcitrance and to identifying the best severity conditions to optimise HWP in sustainable biorefineries.
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Affiliation(s)
- Amandine Leroy
- INRAE, UR 1268 BIA, 44316, Nantes, France
- Université de Reims Champagne Ardenne, INRAE, FARE, UMR A614, 51100, Reims, France
| | - Xavier Falourd
- INRAE, UR 1268 BIA, 44316, Nantes, France
- INRAE, BIBS Facility, 44316, Nantes, France
| | - Loïc Foucat
- INRAE, UR 1268 BIA, 44316, Nantes, France
- INRAE, BIBS Facility, 44316, Nantes, France
| | - Valérie Méchin
- INRAE, Institut Jean-Pierre Bourgin, 78026, Versailles, France
| | | | - Gabriel Paës
- Université de Reims Champagne Ardenne, INRAE, FARE, UMR A614, 51100, Reims, France.
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Novy V, Nielsen F, Cullen D, Sabat G, Houtman CJ, Hunt CG. The characteristics of insoluble softwood substrates affect fungal morphology, secretome composition, and hydrolytic efficiency of enzymes produced by Trichoderma reesei. BIOTECHNOLOGY FOR BIOFUELS 2021; 14:105. [PMID: 33902680 PMCID: PMC8074412 DOI: 10.1186/s13068-021-01955-5] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/20/2021] [Accepted: 04/11/2021] [Indexed: 05/04/2023]
Abstract
BACKGROUND On-site enzyme production using Trichoderma reesei can improve yields and lower the overall cost of lignocellulose saccharification by exploiting the fungal gene regulatory mechanism that enables it to continuously adapt enzyme secretion to the substrate used for cultivation. To harness this, the interrelation between substrate characteristics and fungal response must be understood. However, fungal morphology or gene expression studies often lack structural and chemical substrate characterization. Here, T. reesei QM6a was cultivated on three softwood substrates: northern bleached softwood Kraft pulp (NBSK) and lodgepole pine pretreated either by dilute-acid-catalyzed steam pretreatment (LP-STEX) or mild alkaline oxidation (LP-ALKOX). With different pretreatments of similar starting materials, we presented the fungus with systematically modified substrates. This allowed the elucidation of substrate-induced changes in the fungal response and the testing of the secreted enzymes' hydrolytic strength towards the same substrates. RESULTS Enzyme activity time courses correlated with hemicellulose content and cellulose accessibility. Specifically, increased amounts of side-chain-cleaving hemicellulolytic enzymes in the protein produced on the complex substrates (LP-STEX; LP-ALKOX) was observed by secretome analysis. Confocal laser scanning micrographs showed that fungal micromorphology responded to changes in cellulose accessibility and initial culture viscosity. The latter was caused by surface charge and fiber dimensions, and likely restricted mass transfer, resulting in morphologies of fungi in stress. Supplementing a basic cellulolytic enzyme mixture with concentrated T. reesei supernatant improved saccharification efficiencies of the three substrates, where cellulose, xylan, and mannan conversion was increased by up to 27, 45, and 2800%, respectively. The improvement was most pronounced for proteins produced on LP-STEX and LP-ALKOX on those same substrates, and in the best case, efficiencies reached those of a state-of-the-art commercial enzyme preparation. CONCLUSION Cultivation of T. reesei on LP-STEX and LP-ALKOX produced a protein mixture that increased the hydrolytic strength of a basic cellulase mixture to state-of-the-art performance on softwood substrates. This suggests that the fungal adaptation mechanism can be exploited to achieve enhanced performance in enzymatic hydrolysis without a priori knowledge of specific substrate requirements.
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Affiliation(s)
- Vera Novy
- US Department of Agriculture, Forest Products Laboratory, One Gifford Pinchot Drive, Madison, WI, 53726, USA.
- Department of Biology and Bioengineering, Division of Industrial Biotechnology, Chalmers University of Technology, Kemivägen 10, 412 96, Göteborg, Sweden.
| | - Fredrik Nielsen
- US Department of Agriculture, Forest Products Laboratory, One Gifford Pinchot Drive, Madison, WI, 53726, USA
| | - Daniel Cullen
- US Department of Agriculture, Forest Products Laboratory, One Gifford Pinchot Drive, Madison, WI, 53726, USA
| | - Grzegorz Sabat
- University of Wisconsin Biotechnology Center, Madison, WI, 53706, USA
| | - Carl J Houtman
- US Department of Agriculture, Forest Products Laboratory, One Gifford Pinchot Drive, Madison, WI, 53726, USA
| | - Christopher G Hunt
- US Department of Agriculture, Forest Products Laboratory, One Gifford Pinchot Drive, Madison, WI, 53726, USA
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Wu J, Chandra RP, Takada M, Liu LY, Renneckar S, Kim KH, Kim CS, Saddler JN. Enhancing Enzyme-Mediated Cellulose Hydrolysis by Incorporating Acid Groups Onto the Lignin During Biomass Pretreatment. Front Bioeng Biotechnol 2020; 8:608835. [PMID: 33282856 PMCID: PMC7691530 DOI: 10.3389/fbioe.2020.608835] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2020] [Accepted: 10/26/2020] [Indexed: 11/13/2022] Open
Abstract
Lignin is known to limit the enzyme-mediated hydrolysis of biomass by both restricting substrate swelling and binding to the enzymes. Pretreated mechanical pulp (MP) made from Aspen wood chips was incubated with either 16% sodium sulfite or 32% sodium percarbonate to incorporate similar amounts of sulfonic and carboxylic acid groups onto the lignin (60 mmol/kg substrate) present in the pulp without resulting in significant delignification. When Simon's stain was used to assess potential enzyme accessibility to the cellulose, it was apparent that both post-treatments enhanced accessibility and cellulose hydrolysis. To further elucidate how acid group addition might influence potential enzyme binding to lignin, Protease Treated Lignin (PTL) was isolated from the original and modified mechanical pulps and added to a cellulose rich, delignified Kraft pulp. As anticipated, the PTLs from both the oxidized and sulfonated substrates proved less inhibitory and adsorbed less enzymes than did the PTL derived from the original pulp. Subsequent analyses indicated that both the sulfonated and oxidized lignin samples contained less phenolic hydroxyl groups, resulting in enhanced hydrophilicity and a more negative charge which decreased the non-productive binding of the cellulase enzymes to the lignin.
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Affiliation(s)
- Jie Wu
- Forest Product Biotechnology/Bioenergy Group, Department of Wood Science, Faculty of Forestry, University of British Columbia, Vancouver, BC, Canada
| | - Richard P Chandra
- Forest Product Biotechnology/Bioenergy Group, Department of Wood Science, Faculty of Forestry, University of British Columbia, Vancouver, BC, Canada
| | - Masatsugu Takada
- Forest Product Biotechnology/Bioenergy Group, Department of Wood Science, Faculty of Forestry, University of British Columbia, Vancouver, BC, Canada.,International Advanced Energy Science Research and Education Center, Graduate School of Energy Science, Kyoto University, Kyoto, Japan
| | - Li-Yang Liu
- Advanced Renewable Materials Lab, Department of Wood Science, Faculty of Forestry, University of British Columbia, Vancouver, BC, Canada
| | - Scott Renneckar
- Advanced Renewable Materials Lab, Department of Wood Science, Faculty of Forestry, University of British Columbia, Vancouver, BC, Canada
| | - Kwang Ho Kim
- Clean Energy Research Center, Korea Institute of Science and Technology, Seoul, South Korea
| | - Chang Soo Kim
- Clean Energy Research Center, Korea Institute of Science and Technology, Seoul, South Korea
| | - Jack N Saddler
- Forest Product Biotechnology/Bioenergy Group, Department of Wood Science, Faculty of Forestry, University of British Columbia, Vancouver, BC, Canada
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10
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Wu J, Chandra R, Takada M, Del Rio P, Kim KH, Kim CS, Liu LY, Renneckar S, Saddler J. Alkaline sulfonation and thermomechanical pulping pretreatment of softwood chips and pellets to enhance enzymatic hydrolysis. BIORESOURCE TECHNOLOGY 2020; 315:123789. [PMID: 32682260 DOI: 10.1016/j.biortech.2020.123789] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/28/2020] [Revised: 06/30/2020] [Accepted: 07/01/2020] [Indexed: 06/11/2023]
Abstract
To assess the impact of alkalinity on sulfonation and the enzyme-mediated hydrolysis of softwood cellulose, Lodgepole pine chips were impregnated with 8% sodium sulfite and increasing loadings of sodium carbonate before thermomechanical pulping. It was apparent that alkali addition enhanced lignin sulfonation with an additional 4% loading of sodium carbonate proving optimal. TEM indicated that sulfonation predominantly occurred within the secondary-cell-wall lignin, increasing cellulose accessibility to the cellulase enzymes. Although increasing alkalinity did not significantly enhance lignin sulfonation, likely due to the lower acetyl content of the softwood chips, it increases mannan solubilization. Despite their smaller particle size, softwood pellets were more poorly sulfonated, probably due to their higher lignin content and lower amount of acid groups. This more condensed lignin structure was confirmed by 2D-NMR and GPC analyses which indicated that the EMAL derived from softwood pellets contained less native β-O-4 linkages and had a higher molecular weight.
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Affiliation(s)
- Jie Wu
- Forest Product Biotechnology/Bioenergy Group, Department of Wood Science, Faculty of Forestry, University of British Columbia, 2424 Main Mall, Vancouver, BC V6T 1 Z4, Canada
| | - Richard Chandra
- Forest Product Biotechnology/Bioenergy Group, Department of Wood Science, Faculty of Forestry, University of British Columbia, 2424 Main Mall, Vancouver, BC V6T 1 Z4, Canada
| | - Masatsugu Takada
- Forest Product Biotechnology/Bioenergy Group, Department of Wood Science, Faculty of Forestry, University of British Columbia, 2424 Main Mall, Vancouver, BC V6T 1 Z4, Canada; International Advanced Energy Science Research and Education Center, Graduate School of Energy Science, Kyoto University, 301, Faculty of Engineering Integrated Research Building, Yoshida-Honmachi, Kyoto 606-850, Japan
| | - Pablo Del Rio
- Forest Product Biotechnology/Bioenergy Group, Department of Wood Science, Faculty of Forestry, University of British Columbia, 2424 Main Mall, Vancouver, BC V6T 1 Z4, Canada; Department of Chemical Engineering, Faculty of Science, University of Vigo, As Lagoas, 32004 Ourense, Spain
| | - Kwang Ho Kim
- Clean Energy Research Center, Korea Institute of Science and Technology, Hwarangno 14-gil 5, Seongbuk-gu, Seul 136-791, Republic of Korea
| | - Chang Soo Kim
- Clean Energy Research Center, Korea Institute of Science and Technology, Hwarangno 14-gil 5, Seongbuk-gu, Seul 136-791, Republic of Korea
| | - Li-Yang Liu
- Advanced Renewable Materials Lab, Department of Wood Science, Faculty of Forestry, University of British Columbia, 2424 Main Mall, Vancouver, BC V6T 1 Z4, Canada
| | - Scott Renneckar
- Advanced Renewable Materials Lab, Department of Wood Science, Faculty of Forestry, University of British Columbia, 2424 Main Mall, Vancouver, BC V6T 1 Z4, Canada
| | - Jack Saddler
- Forest Product Biotechnology/Bioenergy Group, Department of Wood Science, Faculty of Forestry, University of British Columbia, 2424 Main Mall, Vancouver, BC V6T 1 Z4, Canada.
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11
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Mboowa D, Khatri V, Saddler JN. The use of fluorescent protein-tagged carbohydrate-binding modules to evaluate the influence of drying on cellulose accessibility and enzymatic hydrolysis. RSC Adv 2020; 10:27152-27160. [PMID: 35515757 PMCID: PMC9055586 DOI: 10.1039/d0ra05333c] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2020] [Accepted: 07/12/2020] [Indexed: 11/21/2022] Open
Abstract
The influence of drying on cellulose accessibility and enzymatic hydrolysis was assessed. Dissolving pulp was differentially dried by freeze-, air- and oven-drying at 50 °C and subsequently hydrolyzed using the commercial CTec 3 cellulase preparation. It was apparent that drying reduced the ease of enzymatic hydrolysis of all of the substrates with a pronounced reduction (48%) exhibited by the oven-dried pulp. To assess if the ease of hydrolysis was due to enzyme accessibility to the substrate, microscopy (SEM), FTIR spectroscopy, water retention value (WRV), fiber aspect ratio analysis, Simons' stain and the selective binding of Fluorescent Protein-tagged Carbohydrate Binding Modules (FP-CBMs): CBM3a (crystalline cellulose) and CBM17 (amorphous cellulose) in combination with confocal laser scanning microscopy (CLSM) were used. The combined methods indicated that, if the gross characteristics of the substrate limited enzyme accessibility, the cellulases, as represented by the FP-CBMs, could not in turn access the finer structural components of the cellulosic substrates. Drying restricts cellulose accessibility at macro- and micro-scale of fiber structure with restriction at macro-fiber significantly limiting accessibility to micro-fibrils.![]()
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Affiliation(s)
- Drake Mboowa
- Forest Products Biotechnology/Bioenergy Group, Faculty of Forestry, Department of Wood Science, University of British Columbia 2424 main mall Vancouver BC V6T 1Z4 Canada
| | - Vinay Khatri
- Forest Products Biotechnology/Bioenergy Group, Faculty of Forestry, Department of Wood Science, University of British Columbia 2424 main mall Vancouver BC V6T 1Z4 Canada
| | - Jack N Saddler
- Forest Products Biotechnology/Bioenergy Group, Faculty of Forestry, Department of Wood Science, University of British Columbia 2424 main mall Vancouver BC V6T 1Z4 Canada
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12
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Enzymatic Hydrolysis of Softwood Derived Paper Sludge by an In Vitro Recombinant Cellulase Cocktail for the Production of Fermentable Sugars. Catalysts 2020. [DOI: 10.3390/catal10070775] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Paper sludge is an attractive biomass feedstock for bioconversion to ethanol due to its low cost and the lack of pretreatment required for its bioprocessing. This study assessed the use of a recombinant cellulase cocktail (mono-components: S. cerevisiae-derived PcBGL1B (BGL), TeCel7A (CBHI), ClCel6A (CBHII) and TrCel5A (EGII) mono-component cellulase enzymes) for the efficient saccharification of softwood-derived paper sludge to produce fermentable sugars. The paper sludge mainly contained 74.3% moisture and 89.7% (per dry mass (DM)) glucan with a crystallinity index of 91.5%. The optimal protein ratio for paper sludge hydrolysis was observed at 9.4: 30.2: 30.2: 30.2% for BGL: CBHI: CBHII: EGII. At a protein loading of 7.5 mg/g DW paper sludge, the yield from hydrolysis was approximately 80%, based on glucan, with scanning electron microscopy micrographs indicating a significant alteration in the microfibril size (length reduced from ≥ 2 mm to 93 µm) of the paper sludge. The paper sludge hydrolysis potential of the Opt CelMix (formulated cellulase cocktail) was similar to the commercial Cellic CTec2® and Celluclast® 1.5 L cellulase preparations and better than Viscozyme® L. Low enzyme loadings (15 mg/g paper sludge) of the Opt CelMix and solid loadings ranging between 1 to 10% (w/v) rendered over 80% glucan conversion. The high glucose yields attained on the paper sludge by the low enzyme loading of the Opt CelMix demonstrated the value of enzyme cocktail optimisation on specific substrates for efficient cellulose conversion to fermentable sugars.
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13
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Wang Z, Pawar PMA, Derba-Maceluch M, Hedenström M, Chong SL, Tenkanen M, Jönsson LJ, Mellerowicz EJ. Hybrid Aspen Expressing a Carbohydrate Esterase Family 5 Acetyl Xylan Esterase Under Control of a Wood-Specific Promoter Shows Improved Saccharification. FRONTIERS IN PLANT SCIENCE 2020; 11:380. [PMID: 32322259 PMCID: PMC7156598 DOI: 10.3389/fpls.2020.00380] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/17/2019] [Accepted: 03/17/2020] [Indexed: 05/12/2023]
Abstract
Fast-growing broad-leaf tree species can serve as feedstocks for production of bio-based chemicals and fuels through biochemical conversion of wood to monosaccharides. This conversion is hampered by the xylan acetylation pattern. To reduce xylan acetylation in the wood, the Hypocrea jecorina acetyl xylan esterase (HjAXE) from carbohydrate esterase (CE) family 5 was expressed in hybrid aspen under the control of the wood-specific PtGT43B promoter and targeted to the secretory pathway. The enzyme was predicted to deacetylate polymeric xylan in the vicinity of cellulose due to the presence of a cellulose-binding module. Cell-wall-bound protein fractions from developing wood of transgenic plants were capable of releasing acetyl from finely ground wood powder, indicative of active AXE present in cell walls of these plants, whereas no such activity was detected in wild-type plants. The transgenic lines grew in height and diameter as well as wild-type trees, whereas their internodes were slightly shorter, indicating higher leaf production. The average acetyl content in the wood of these lines was reduced by 13%, mainly due to reductions in di-acetylated xylose units, and in C-2 and C-3 mono-acetylated xylose units. Analysis of soluble cell wall polysaccharides revealed a 4% reduction in the fraction of xylose units and an 18% increase in the fraction of glucose units, whereas the contents of cellulose and lignin were not affected. Enzymatic saccharification of wood from transgenic plants resulted in 27% higher glucose yield than for wild-type plants. Brunauer-Emmett-Teller (BET) analysis and Simons' staining pointed toward larger surface area and improved cellulose accessibility for wood from transgenic plants compared to wood from wild-type plants, which could be achieved by HjAXE deacetylating xylan bound to cellulose. The results show that CE5 family can serve as a source of enzymes for in planta reduction of recalcitrance to saccharification.
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Affiliation(s)
- Zhao Wang
- Department of Chemistry, KBC Chemical-Biological Centre, Umeå University, Umeå, Sweden
| | | | - Marta Derba-Maceluch
- Department of Forest Genetics and Plant Physiology, Swedish University of Agricultural Sciences, Umeå, Sweden
| | - Mattias Hedenström
- Department of Chemistry, KBC Chemical-Biological Centre, Umeå University, Umeå, Sweden
| | - Sun-Li Chong
- Department of Food and Environmental Sciences, University of Helsinki, Helsinki, Finland
| | - Maija Tenkanen
- Department of Food and Environmental Sciences, University of Helsinki, Helsinki, Finland
| | - Leif J. Jönsson
- Department of Chemistry, KBC Chemical-Biological Centre, Umeå University, Umeå, Sweden
| | - Ewa J. Mellerowicz
- Department of Forest Genetics and Plant Physiology, Swedish University of Agricultural Sciences, Umeå, Sweden
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14
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van der Zwan T, Chandra RP, Saddler JN. Laccase-mediated hydrophilization of lignin decreases unproductive enzyme binding but limits subsequent enzymatic hydrolysis at high substrate concentrations. BIORESOURCE TECHNOLOGY 2019; 292:121999. [PMID: 31446388 DOI: 10.1016/j.biortech.2019.121999] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/07/2019] [Revised: 08/09/2019] [Accepted: 08/10/2019] [Indexed: 06/10/2023]
Abstract
One of the predominant mechanisms by which lignin restricts effective enzymatic deconstruction of lignocellulosic materials is the unproductive adsorption of enzymes. Although this inhibition can be partially mitigated through hydrophilization of lignin during thermochemical pretreatment, these types of treatments could potentially worsen slurry rheology, consequently making it more difficult to process the material at high substrate concentrations. In the work reported here, laccases were used to specifically modify lignin hydrophilicity within steam-pretreated substrate via in situ phenolic compound grafting. While lignin hydrophilization reduced unproductive enzyme adsorption, high-solids hydrolysis efficiency decreased significantly due to mass transfer limitations. It was apparent that low-solids hydrolysis experiments were a poor predictor of substrate digestibility at high-solids conditions and that substrate-water interactions impacted both substrate digestibility and slurry rheology.
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Affiliation(s)
- Timo van der Zwan
- Forest Products Biotechnology and Bioenergy Group, Department of Wood Science, Faculty of Forestry, The University of British Columbia, 2424 Main Mall, Vancouver, British Columbia V6T 1Z4, Canada
| | - Richard P Chandra
- Forest Products Biotechnology and Bioenergy Group, Department of Wood Science, Faculty of Forestry, The University of British Columbia, 2424 Main Mall, Vancouver, British Columbia V6T 1Z4, Canada
| | - Jack N Saddler
- Forest Products Biotechnology and Bioenergy Group, Department of Wood Science, Faculty of Forestry, The University of British Columbia, 2424 Main Mall, Vancouver, British Columbia V6T 1Z4, Canada.
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15
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Wang Z, Wu G, Jönsson LJ. Effects of impregnation of softwood with sulfuric acid and sulfur dioxide on chemical and physical characteristics, enzymatic digestibility, and fermentability. BIORESOURCE TECHNOLOGY 2018; 247:200-208. [PMID: 28950127 DOI: 10.1016/j.biortech.2017.09.081] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/26/2017] [Revised: 09/09/2017] [Accepted: 09/11/2017] [Indexed: 05/02/2023]
Abstract
Hydrothermal pretreatment improves bioconversion of lignocellulose, but the effects of different acid catalysts are poorly understood. The effects of sulfuric acid (SA) and sulfur dioxide (SD) in continuous steam pretreatment of wood of Norway spruce were compared in the temperature range 195°C-215°C. The inhibitory effects of the pretreatment liquid on cellulolytic enzymes and Saccharomyces cerevisiae yeast were higher for SD- than for SA-pretreated material, and the inhibitory effects increased with increasing pretreatment temperature. However, the susceptibility to cellulolytic enzymes of wood pretreated with SD was 2.0-2.9 times higher than that of wood pretreated with SA at the same temperature. Data conclusively show that the superior convertibility of SD-pretreated material was not due to inhibition phenomena but rather to the greater capability of the SD pretreatment to reduce the particle size through partial delignification and cellulose degradation. Particle size was shown to be correlated with enzymatic digestibility (R2 0.97-0.98).
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Affiliation(s)
- Zhao Wang
- Department of Chemistry, Umeå University, SE-901 87 Umeå, Sweden
| | - Guochao Wu
- Department of Chemistry, Umeå University, SE-901 87 Umeå, Sweden
| | - Leif J Jönsson
- Department of Chemistry, Umeå University, SE-901 87 Umeå, Sweden.
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16
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Li M, Pu Y, Yoo CG, Gjersing E, Decker SR, Doeppke C, Shollenberger T, Tschaplinski TJ, Engle NL, Sykes RW, Davis MF, Baxter HL, Mazarei M, Fu C, Dixon RA, Wang ZY, Neal Stewart C, Ragauskas AJ. Study of traits and recalcitrance reduction of field-grown COMT down-regulated switchgrass. BIOTECHNOLOGY FOR BIOFUELS 2017; 10:12. [PMID: 28053668 PMCID: PMC5209956 DOI: 10.1186/s13068-016-0695-7] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/17/2016] [Accepted: 12/23/2016] [Indexed: 05/22/2023]
Abstract
BACKGROUND The native recalcitrance of plants hinders the biomass conversion process using current biorefinery techniques. Down-regulation of the caffeic acid O-methyltransferase (COMT) gene in the lignin biosynthesis pathway of switchgrass reduced the thermochemical and biochemical conversion recalcitrance of biomass. Due to potential environmental influences on lignin biosynthesis and deposition, studying the consequences of physicochemical changes in field-grown plants without pretreatment is essential to evaluate the performance of lignin-altered plants. We determined the chemical composition, cellulose crystallinity and the degree of its polymerization, molecular weight of hemicellulose, and cellulose accessibility of cell walls in order to better understand the fundamental features of why biomass is recalcitrant to conversion without pretreatment. The most important is to investigate whether traits and features are stable in the dynamics of field environmental effects over multiple years. RESULTS Field-grown COMT down-regulated plants maintained both reduced cell wall recalcitrance and lignin content compared with the non-transgenic controls for at least 3 seasons. The transgenic switchgrass yielded 35-84% higher total sugar release (enzymatic digestibility or saccharification) from a 72-h enzymatic hydrolysis without pretreatment and also had a 25-32% increase in enzymatic sugar release after hydrothermal pretreatment. The COMT-silenced switchgrass lines had consistently lower lignin content, e.g., 12 and 14% reduction for year 2 and year 3 growing season, respectively, than the control plants. By contrast, the transgenic lines had 7-8% more xylan and galactan contents than the wild-type controls. Gel permeation chromatographic results revealed that the weight-average molecular weights of hemicellulose were 7-11% lower in the transgenic than in the control lines. In addition, we found that silencing of COMT in switchgrass led to 20-22% increased cellulose accessibility as measured by the Simons' stain protocol. No significant changes were observed on the arabinan and glucan contents, cellulose crystallinity, and cellulose degree of polymerization between the transgenic and control plants. With the 2-year comparative analysis, both the control and transgenic lines had significant increases in lignin and glucan contents and hemicellulose molecular weight across the growing seasons. CONCLUSIONS The down-regulation of COMT in switchgrass resulting in a reduced lignin content and biomass recalcitrance is stable in a field-grown trial for at least three seasons. Among the determined affecting factors, the reduced biomass recalcitrance of the COMT-silenced switchgrass, grown in the field conditions for two and three seasons, was likely related to the decreased lignin content and increased biomass accessibility, whereas the cellulose crystallinity and degree of its polymerization and hemicellulose molecular weights did not contribute to the reduction of recalcitrance significantly. This finding suggests that lignin down-regulation in lignocellulosic feedstock confers improved saccharification that translates from greenhouse to field trial and that lignin content and biomass accessibility are two significant factors for developing a reduced recalcitrance feedstock by genetic modification.
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Affiliation(s)
- Mi Li
- BioEnergy Science Center (BESC), Oak Ridge National Laboratory (ORNL), Oak Ridge, TN USA
- BioSciences Division, ORNL, Oak Ridge, TN USA
- UT-ORNL Joint Institute for Biological Sciences, Oak Ridge, TN USA
| | - Yunqiao Pu
- BioEnergy Science Center (BESC), Oak Ridge National Laboratory (ORNL), Oak Ridge, TN USA
- BioSciences Division, ORNL, Oak Ridge, TN USA
- UT-ORNL Joint Institute for Biological Sciences, Oak Ridge, TN USA
| | - Chang Geun Yoo
- BioEnergy Science Center (BESC), Oak Ridge National Laboratory (ORNL), Oak Ridge, TN USA
- BioSciences Division, ORNL, Oak Ridge, TN USA
- UT-ORNL Joint Institute for Biological Sciences, Oak Ridge, TN USA
| | - Erica Gjersing
- Biosciences Center, National Renewable Energy Laboratory (NREL), Golden, CO USA
| | - Stephen R. Decker
- Biosciences Center, National Renewable Energy Laboratory (NREL), Golden, CO USA
| | - Crissa Doeppke
- Biosciences Center, National Renewable Energy Laboratory (NREL), Golden, CO USA
| | - Todd Shollenberger
- Biosciences Center, National Renewable Energy Laboratory (NREL), Golden, CO USA
| | - Timothy J. Tschaplinski
- BioEnergy Science Center (BESC), Oak Ridge National Laboratory (ORNL), Oak Ridge, TN USA
- BioSciences Division, ORNL, Oak Ridge, TN USA
- UT-ORNL Joint Institute for Biological Sciences, Oak Ridge, TN USA
| | - Nancy L. Engle
- BioEnergy Science Center (BESC), Oak Ridge National Laboratory (ORNL), Oak Ridge, TN USA
- BioSciences Division, ORNL, Oak Ridge, TN USA
- UT-ORNL Joint Institute for Biological Sciences, Oak Ridge, TN USA
| | | | | | - Holly L. Baxter
- BioEnergy Science Center (BESC), Oak Ridge National Laboratory (ORNL), Oak Ridge, TN USA
- Department of Plant Sciences, University of Tennessee, Knoxville, TN USA
| | - Mitra Mazarei
- BioEnergy Science Center (BESC), Oak Ridge National Laboratory (ORNL), Oak Ridge, TN USA
- Department of Plant Sciences, University of Tennessee, Knoxville, TN USA
| | - Chunxiang Fu
- Forage Improvement Division, The Samuel Roberts Noble Foundation, Ardmore, OK USA
| | - Richard A. Dixon
- BioEnergy Science Center (BESC), Oak Ridge National Laboratory (ORNL), Oak Ridge, TN USA
- BioDiscovery Institute and Department of Biological Sciences, University of North Texas, Denton, TX USA
| | - Zeng-Yu Wang
- BioEnergy Science Center (BESC), Oak Ridge National Laboratory (ORNL), Oak Ridge, TN USA
- Forage Improvement Division, The Samuel Roberts Noble Foundation, Ardmore, OK USA
| | - C. Neal Stewart
- BioEnergy Science Center (BESC), Oak Ridge National Laboratory (ORNL), Oak Ridge, TN USA
- Department of Plant Sciences, University of Tennessee, Knoxville, TN USA
| | - Arthur J. Ragauskas
- BioEnergy Science Center (BESC), Oak Ridge National Laboratory (ORNL), Oak Ridge, TN USA
- BioSciences Division, ORNL, Oak Ridge, TN USA
- UT-ORNL Joint Institute for Biological Sciences, Oak Ridge, TN USA
- Department of Chemical and Biomolecular Engineering & Department of Forestry, Wildlife and Fisheries, University of Tennessee, Knoxville, TN USA
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17
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Siqueira G, Arantes V, Saddler JN, Ferraz A, Milagres AMF. Limitation of cellulose accessibility and unproductive binding of cellulases by pretreated sugarcane bagasse lignin. BIOTECHNOLOGY FOR BIOFUELS 2017; 10:176. [PMID: 28702081 PMCID: PMC5504807 DOI: 10.1186/s13068-017-0860-7] [Citation(s) in RCA: 47] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/23/2017] [Accepted: 06/27/2017] [Indexed: 05/03/2023]
Abstract
BACKGROUND The effectiveness of the enzymatic hydrolysis of cellulose in plant cell wall is strongly influenced by the access of enzymes to cellulose, which is at least in part limited by the presence of lignin. Although physicochemical treatments preceding the enzymatic catalysis significantly overcome this recalcitrance, the residual lignin can still play a role in the process. Lignin is suggested to act as a barrier, hindering cellulose and limiting the access of the enzymes. It can also unspecifically bind cellulases, reducing the amount of enzymes available to act on cellulose. However, the limiting role of the lignin present in pretreated sugarcane bagasses has not been fully understood yet. RESULTS A set of sugarcane bagasses pretreated by five leading pretreatment technologies was created and used to assess their accessibility and the unproductive binding capacity of the resulting lignins. Steam explosion and alkaline sulfite pretreatments resulted in more accessible substrates, with approximately 90% of the cellulose hydrolyzed using high enzyme loadings. Enzymatic hydrolysis of alkaline-treated (NaOH) and steam-exploded sugarcane bagasses were strongly affected by unproductive binding at the lowest enzyme loading tested. Analysis of the extracted lignins confirmed the superior binding capacity of these lignins. Sulfite-based pretreatments (alkaline sulfite and acid sulfite) resulted in lignins with lower binding capacities compared to the analogue pretreatments without sulfite (alkaline and acidic). Strong acid groups present in sulfite-based pretreated substrates, attributed to sulfonated lignins, corroborated the lower binding capacities of the lignin present in these substrates. A more advanced enzyme preparation (Cellic CTec3) was shown to be less affected by unproductive binding at low enzyme loading. CONCLUSIONS Pretreatments that increase the accessibility and modify the lignin are necessary in order to decrease the protein binding capacity. The search for the called weak lignin-binding enzymes is of major importance if hydrolysis with low enzyme loadings is the goal for economically viable processes.
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Affiliation(s)
- Germano Siqueira
- Departamento de Biotecnologia, Escola de Engenharia de Lorena, Universidade de São Paulo, CP 116, Lorena, SP 12602-810 Brazil
- Forest Products Biotechnology/Bioenergy Group, Faculty of Forestry, University of British Columbia, 2424 Main Mall, Vancouver, BC V6T 1Z4 Canada
| | - Valdeir Arantes
- Departamento de Biotecnologia, Escola de Engenharia de Lorena, Universidade de São Paulo, CP 116, Lorena, SP 12602-810 Brazil
- Forest Products Biotechnology/Bioenergy Group, Faculty of Forestry, University of British Columbia, 2424 Main Mall, Vancouver, BC V6T 1Z4 Canada
| | - Jack N. Saddler
- Forest Products Biotechnology/Bioenergy Group, Faculty of Forestry, University of British Columbia, 2424 Main Mall, Vancouver, BC V6T 1Z4 Canada
| | - André Ferraz
- Departamento de Biotecnologia, Escola de Engenharia de Lorena, Universidade de São Paulo, CP 116, Lorena, SP 12602-810 Brazil
| | - Adriane M. F. Milagres
- Departamento de Biotecnologia, Escola de Engenharia de Lorena, Universidade de São Paulo, CP 116, Lorena, SP 12602-810 Brazil
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18
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Wang S, Ouyang X, Wang W, Yuan Q, Yan A. Comparison of ultrasound-assisted Fenton reaction and dilute acid-catalysed steam explosion pretreatment of corncobs: cellulose characteristics and enzymatic saccharification. RSC Adv 2016. [DOI: 10.1039/c6ra13125e] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
As an emerging method for lignocellulose pretreatment, the ultrasound-assisted Fenton reaction is not well developed in comparison to the dilute acid-catalysed steam explosion.
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Affiliation(s)
- Sujun Wang
- College of Life Science and Technology
- Beijing University of Chemical Technology
- Beijing 100029
- China
| | - Xianhong Ouyang
- College of Life Science and Technology
- Beijing University of Chemical Technology
- Beijing 100029
- China
| | - Wenya Wang
- College of Life Science and Technology
- Beijing University of Chemical Technology
- Beijing 100029
- China
| | - Qipeng Yuan
- College of Life Science and Technology
- Beijing University of Chemical Technology
- Beijing 100029
- China
| | - Aixia Yan
- College of Life Science and Technology
- Beijing University of Chemical Technology
- Beijing 100029
- China
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19
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Dumitrache A, Akinosho H, Rodriguez M, Meng X, Yoo CG, Natzke J, Engle NL, Sykes RW, Tschaplinski TJ, Muchero W, Ragauskas AJ, Davison BH, Brown SD. Consolidated bioprocessing of Populus using Clostridium (Ruminiclostridium) thermocellum: a case study on the impact of lignin composition and structure. BIOTECHNOLOGY FOR BIOFUELS 2016; 9:31. [PMID: 26855670 PMCID: PMC4743434 DOI: 10.1186/s13068-016-0445-x] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/05/2015] [Accepted: 01/20/2016] [Indexed: 05/04/2023]
Abstract
BACKGROUND Higher ratios of syringyl-to-guaiacyl (S/G) lignin components of Populus were shown to improve sugar release by enzymatic hydrolysis using commercial blends. Cellulolytic microbes are often robust biomass hydrolyzers and may offer cost advantages; however, it is unknown whether their activity can also be significantly influenced by the ratio of different monolignol types in Populus biomass. Hydrolysis and fermentation of autoclaved, but otherwise not pretreated Populus trichocarpa by Clostridium thermocellum ATCC 27405 was compared using feedstocks that had similar carbohydrate and total lignin contents but differed in S/G ratios. RESULTS Populus with an S/G ratio of 2.1 was converted more rapidly and to a greater extent compared to similar biomass that had a ratio of 1.2. For either microbes or commercial enzymes, an approximate 50 % relative difference in total solids solubilization was measured for both biomasses, which suggests that the differences and limitations in the microbial breakdown of lignocellulose may be largely from the enzymatic hydrolytic process. Surprisingly, the reduction in glucan content per gram solid in the residual microbially processed biomass was similar (17-18 %) irrespective of S/G ratio, pointing to a similar mechanism of solubilization that proceeded at different rates. Fermentation metabolome testing did not reveal the release of known biomass-derived alcohol and aldehyde inhibitors that could explain observed differences in microbial hydrolytic activity. Biomass-derived p-hydroxybenzoic acid was up to nine-fold higher in low S/G ratio biomass fermentations, but was not found to be inhibitory in subsequent test fermentations. Cellulose crystallinity and degree of polymerization did not vary between Populus lines and had minor changes after fermentation. However, lignin molecular weights and cellulose accessibility determined by Simons' staining were positively correlated to the S/G content. CONCLUSIONS Higher S/G ratios in Populus biomass lead to longer and more linear lignin chains and greater access to surface cellulosic content by microbe-bound enzymatic complexes. Substrate access limitation is suggested as a primary bottleneck in solubilization of minimally processed Populus, which has important implications for microbial deconstruction of lignocellulose biomass. Our findings will allow others to examine different Populus lines and to test if similar observations are possible for other plant species.
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Affiliation(s)
- Alexandru Dumitrache
- />Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831 USA
- />BioEnergy Sciences Center, Bioscience Division, Oak Ridge National Laboratory, Oak Ridge, TN 37830 USA
| | - Hannah Akinosho
- />Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831 USA
- />BioEnergy Sciences Center, Bioscience Division, Oak Ridge National Laboratory, Oak Ridge, TN 37830 USA
- />Renewable Bioproducts Institute, Georgia Institute of Technology, Atlanta, GA 30332 USA
- />UT-ORNL Joint Institute for Biological Sciences, Oak Ridge National Laboratory, Oak Ridge, TN 37831 USA
| | - Miguel Rodriguez
- />Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831 USA
- />BioEnergy Sciences Center, Bioscience Division, Oak Ridge National Laboratory, Oak Ridge, TN 37830 USA
| | - Xianzhi Meng
- />BioEnergy Sciences Center, Bioscience Division, Oak Ridge National Laboratory, Oak Ridge, TN 37830 USA
- />Renewable Bioproducts Institute, Georgia Institute of Technology, Atlanta, GA 30332 USA
- />School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, GA 30332 USA
| | - Chang Geun Yoo
- />Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831 USA
- />BioEnergy Sciences Center, Bioscience Division, Oak Ridge National Laboratory, Oak Ridge, TN 37830 USA
- />UT-ORNL Joint Institute for Biological Sciences, Oak Ridge National Laboratory, Oak Ridge, TN 37831 USA
| | - Jace Natzke
- />Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831 USA
- />BioEnergy Sciences Center, Bioscience Division, Oak Ridge National Laboratory, Oak Ridge, TN 37830 USA
| | - Nancy L. Engle
- />Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831 USA
- />BioEnergy Sciences Center, Bioscience Division, Oak Ridge National Laboratory, Oak Ridge, TN 37830 USA
| | - Robert W. Sykes
- />National Renewable Energy Laboratory, US Department of Energy, Golden, CO 80401 USA
| | - Timothy J. Tschaplinski
- />Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831 USA
- />BioEnergy Sciences Center, Bioscience Division, Oak Ridge National Laboratory, Oak Ridge, TN 37830 USA
| | - Wellington Muchero
- />Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831 USA
- />BioEnergy Sciences Center, Bioscience Division, Oak Ridge National Laboratory, Oak Ridge, TN 37830 USA
| | - Arthur J. Ragauskas
- />Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831 USA
- />BioEnergy Sciences Center, Bioscience Division, Oak Ridge National Laboratory, Oak Ridge, TN 37830 USA
- />UT-ORNL Joint Institute for Biological Sciences, Oak Ridge National Laboratory, Oak Ridge, TN 37831 USA
- />Department of Chemical and Biomolecular Engineering, Department of Forestry, Wildlife, and Fisheries, University of Tennessee, Knoxville, TN 37996 USA
| | - Brian H. Davison
- />Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831 USA
- />BioEnergy Sciences Center, Bioscience Division, Oak Ridge National Laboratory, Oak Ridge, TN 37830 USA
| | - Steven D. Brown
- />Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831 USA
- />BioEnergy Sciences Center, Bioscience Division, Oak Ridge National Laboratory, Oak Ridge, TN 37830 USA
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Chandra RP, Chu Q, Hu J, Zhong N, Lin M, Lee JS, Saddler J. The influence of lignin on steam pretreatment and mechanical pulping of poplar to achieve high sugar recovery and ease of enzymatic hydrolysis. BIORESOURCE TECHNOLOGY 2016; 199:135-141. [PMID: 26391968 DOI: 10.1016/j.biortech.2015.09.019] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/09/2015] [Revised: 08/31/2015] [Accepted: 09/01/2015] [Indexed: 05/05/2023]
Abstract
With the goal of enhancing overall carbohydrate recovery and reducing enzyme loading refiner mechanical pulping and steam pretreatment (210°C, 5 min) were used to pretreat poplar wood chips. Neutral sulphonation post-treatment indicated that, although the lignin present in the steam pretreated substrate was less reactive, the cellulose-rich, water insoluble component was more accessible to cellulases and Simons stain. This was likely due to lignin relocation as the relative surface lignin measured by X-ray photoelectron spectroscopy increased from 0.4 to 0.8. The integration of sulphite directly into steam pretreatment resulted in the solubilisation of 60% of the lignin while more than 80% of the carbohydrate present in the original substrate was recovered in the water insoluble fraction after Na2CO3 addition. More than 80% of the sugars present in the original cellulose and xylan could be recovered after 48 h using an enzyme loading of 20 mg protein/g cellulose at a 10% substrate concentration.
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Affiliation(s)
- Richard P Chandra
- Forest Products Biotechnology/Bioenergy Group, University of British Columbia, Faculty of Forestry, British Columbia, Canada
| | - QiuLu Chu
- Forest Products Biotechnology/Bioenergy Group, University of British Columbia, Faculty of Forestry, British Columbia, Canada
| | - Jinguang Hu
- Forest Products Biotechnology/Bioenergy Group, University of British Columbia, Faculty of Forestry, British Columbia, Canada
| | - Na Zhong
- Forest Products Biotechnology/Bioenergy Group, University of British Columbia, Faculty of Forestry, British Columbia, Canada
| | - Mandy Lin
- Forest Products Biotechnology/Bioenergy Group, University of British Columbia, Faculty of Forestry, British Columbia, Canada
| | - Jin-Suk Lee
- Clean Fuel Department, Korea Institute of Energy Research, Jeongeup, Jeonbuk 580-185, South Korea
| | - Jack Saddler
- Forest Products Biotechnology/Bioenergy Group, University of British Columbia, Faculty of Forestry, British Columbia, Canada
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Chandra RP, Arantes V, Saddler J. Steam pretreatment of agricultural residues facilitates hemicellulose recovery while enhancing enzyme accessibility to cellulose. BIORESOURCE TECHNOLOGY 2015; 185:302-7. [PMID: 25780906 DOI: 10.1016/j.biortech.2015.02.106] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/13/2015] [Revised: 02/25/2015] [Accepted: 02/26/2015] [Indexed: 05/11/2023]
Abstract
The origins of lignocellulosic biomass and the pretreatment used to enhance enzyme accessibility to the cellulosic component are known to be strongly influenced by various substrate characteristics. To assess the impact that fibre properties might have on enzymatic hydrolysis, seven agricultural residues were characterised before and after steam pretreatment using a single pretreatment condition (190°C, 5min, 3% SO2) previously shown to enhance fractionation and hydrolysis of the cellulosic component of corn stover. When the fibre length, width and coarseness, viscosity, water retention value and cellulose crystallinity were monitored, no clear correlation was observed between any single substrate characteristic and the substrate's ease of enzymatic hydrolysis. However, the amount of hemicellulose that was solubilised during pretreatment correlated (r(2)=0.98) with the effectiveness of enzyme hydrolysis of each pretreated substrate. Simons's staining, to measure the cellulose accessibility, showed good correlation (r(2)=0.83) with hemicellulose removal and the extent of enzymatic hydrolysis.
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Affiliation(s)
- Richard P Chandra
- Forest Products Biotechnology/Bioenergy Group, University of British Columbia, Faculty of Forestry, British Columbia, Canada
| | - Valdeir Arantes
- Lorena School of Engineering, University of São Paulo, Brazil
| | - Jack Saddler
- Forest Products Biotechnology/Bioenergy Group, University of British Columbia, Faculty of Forestry, British Columbia, Canada.
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Nonaka H, Kobayashi A, Funaoka M. Behavior of lignin-binding cellulase in the presence of fresh cellulosic substrate. BIORESOURCE TECHNOLOGY 2013; 135:53-57. [PMID: 23186657 DOI: 10.1016/j.biortech.2012.10.065] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/05/2012] [Revised: 10/12/2012] [Accepted: 10/13/2012] [Indexed: 05/18/2023]
Abstract
A model lignin-binding cellulase was prepared from Trichoderma reesei cellulase and lignocresol, which was synthesized from softwood or hardwood lignin. Filter paper was incubated with the lignocresol-cellulase complex, and it was observed that only a limited amount of cellulase migrated to the filter paper. The cellulase adsorption isotherms for the lignocresols and filter paper were fitted to a Langmuir absorption model, and the determined Langmuir constants were as follows: softwood lignocresol>hardwood lignocresol>>filter paper. The calculations demonstrated that lignin-binding cellulase can potentially be recovered by the addition of a sufficient quantity of cellulosic substrate. As a result, the lignocresol-binding cellulase is highly stable and lignocresol can potentially be used for immobilizing cellulase in the active state.
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Affiliation(s)
- Hiroshi Nonaka
- Graduate School of Bioresources, Mie University, Tsu, Mie 514-8507, Japan.
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