期刊
CHEMSUSCHEM
卷 6, 期 5, 页码 919-927出版社
WILEY-V C H VERLAG GMBH
DOI: 10.1002/cssc.201200859
关键词
adsorption; biomass; biotransformation; enzymes; proteins
资金
- USDA Small Business Innovative Research (SBIR) Phase II project [2010-33610-21589]
- USDA National Institute of Food and Agriculture (NIFA) through the Northwest Advanced Renewables Alliance (NARA) [2011-68005-30416]
- China Excellent Young Scientist Fund [20925622]
We studied the mechanism of the significant enhancement in the enzymatic saccharification of lignocelluloses at an elevated pH of 5.56.0. Four lignin residues with different sulfonic acid contents were isolated from enzymatic hydrolysis of lodgepole pine pretreated by either dilute acid (DA) or sulfite pretreatment to overcome recalcitrance of lignocelluloses (SPORL). The adsorption isotherms of a commercial Trichoderma reesi cellulase cocktail (CTec2) produced by these lignin residues at 50 degrees C were measured in the pH range of 4.56.0. The zeta potentials of these lignin samples were also measured. We discovered that an elevated pH significantly increased the lignin surface charge (negative), which causes lignin to become more hydrophilic and reduces its coordination affinity to cellulase and, consequently, the nonspecific binding of cellulase. The decreased nonspecific cellulase binding to lignin is also attributed to enhanced electrostatic interactions at elevated pH through the increased negative charges of cellulase enzymes with low pI. The results validate the hypothesis that the increases in enzymatic saccharification efficiencies at elevated pH for different pretreated lignocelluloses are solely the result of decreased nonspecific cellulase binding to lignin. This study contradicts the well-established concept that the optimal pH is 4.85.0 for enzymatic hydrolysis using Trichoderma reesi cellulose, which is widely accepted and exclusively practiced in numerous laboratories throughout the world. Because an elevated pH can be easily implemented commercially without capital cost and with minimal operating cost, this study has both scientific importance and practical significance.
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