Xylanase supplementation on enzymatic saccharification of dilute acid pretreated poplars at different severities
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Three pairs of solid substrates from dilute acid pretreatment of two poplar wood samples were enzymatically hydrolyzed by cellulase preparations supplemented with xylanase. Supplementation of xylanase improved cellulose saccharification perhaps due to improved cellulose accessibility by xylan hydrolysis. Total xylan removal directly affected enzymatic cellulose saccharification. Furthermore, xylan removal by pretreatment and xylanase are indifferent to enzymatic cellulose saccharification. However, more enzymatic xylose and glucose yields were obtained for a substrate with lower xylan content after a severer pretreatment at the same xylanase dosage. The effectiveness of xylanase at increased dosages depended on the substrates structure or accessibility. High xylanase dosages were more effective on well pretreated substrates than on under-pretreated substrates with high xylan content. The application sequence of xylanase and cellulase affected cellulose saccharification. This effect varied with substrate accessibility, perhaps due to competition between xylanase and cellulase binding to the substrate.
KeywordsXylanase supplementation Enzymatic hydrolysis/saccharification Poplar/hard wood Pretreatment severity Substrate accessibility
This work was sponsored by the U.S. Forest Service (USFS) through the Program of Woody Biomass, Bioenergy, and Bioproducts (WBBB, 2011), a USDA Small Business Innovative Research (SBIR) Phase II project (Contract Number: 2010-33610-21589) to BioPulping International, and the Agriculture and Food Research Initiative Competitive Grant No. 2011-68005-30416 from the USDA National Institute of Food and Agriculture (NIFA) through the Northwest Advanced Renewables Alliance (NARA). These projects along with the Chinese Scholarship Council (CSC) and the Chinese Academy of Sciences provided financial support to Zhang, Zhuang, and Wang for their visiting appointments at USFS–FPL. We also would like to acknowledge Dr. Ronald Zalesny and his staff at USFS Northern Research Station, Rhinelander, WI, for harvesting the poplar woods.
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