Understanding the effects of lignosulfonate on enzymatic saccharification of pure cellulose
The effects of lignosulfonate (LS) on enzymatic saccharification of pure cellulose were studied. Four fractions of LS with different molecular weight (MW) prepared by ultrafiltration of a commercial LS were applied at different loadings to enzymatic hydrolysis of Whatman paper under different pH. Using LS fractions with low MW and high degree of sulfonation can enhance enzymatic cellulose saccharification despite LS can bind to cellulase nonproductively. The enhancing effect varies with LS properties, its loading, and hydrolysis pH. Inhibitive effect on cellulose saccharification was also observed using LS with large MW and low degree of sulfonation. The concept of “LS-cellulase aggregate stabilized and enhanced cellulase binding” was proposed to explain the observed enhancement of cellulose saccharification. The concept was demonstrated by the linear correlation between the measured amount of bound cellulase and saccharification efficiency with and without LS of different MW in a range of pH.
KeywordsEnzymatic hydrolysis Cellulose saccharification Lignosulfonate Surfactant Cellulase binding Hydrophobic interaction Nonproductive binding
This work was supported by a USDA Small Business Innovative Research (SBIR) phase II project (Phase II project (Contract No. 2010-33610-21589) through Biopulping International, a Agriculture and Food Research Initiative Competitive Grant (2011-68005-30416) from the National Institute of Food and Agriculture (NIFA) through the Northwest Advanced Renewables Alliance (NARA), China Excellent Young Scientist Fund (20925622), International Science and Technology Cooperation Program of China (2013DFA41670), and National Natural Science Foundation of China (21376100), The Chinese Scholarship Council (CSC). These programs made the visiting appointments of Hongming Lou and Haifeng Zhou at the US Forest Service (USFS), Forest Products Laboratory (FPL) possible. We acknowledge Fred Matt and Kolby Hirth (both USFS-FPL) for carrying out carbohydrate and sulfur content analyses. JYZ is a co-inventor of a sulfite pretreatment process—SPORL (US patent application published) that produces lignosulfonate.
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