Accellerase 1000 cellulase, Spezyme CP cellulase, β-glucosidase, Multifect xylanase, and beta-xylosidase were evaluated for hydrolysis of pure cellulose, pure xylan, and switchgrass solids from leading pretreatments of dilute sulfuric acid, sulfur dioxide, liquid hot water, lime, soaking in aqueous ammonia, and ammonia fiber expansion. Distinctive sugar release patterns were observed from Avicel, phosphoric acid swollen cellulose (PASC), xylan, and pretreated switchgrass solids, with accumulation of significant amounts of xylooligomers during xylan hydrolysis. The strong inhibition of cellulose hydrolysis by xylooligomers could be partially attributed to the negative impact of xylooligomers on cellulase adsorption. The digestibility of pretreated switchgrass varied with pretreatment but could not be consistently correlated to xylan, lignin, or acetyl removal. Initial hydrolysis rates did correlate well with cellulase adsorption capacities for all pretreatments except lime, but more investigation is needed to relate this behavior to physical and compositional properties of pretreated switchgrass.
|Number of pages||9|
|State||Published - Dec 2011|
Bibliographical noteFunding Information:
The results reported here were developed to support the Biomass Refining Consortium for Applied Fundamentals and Innovation (CAFI), a partnership among leading pretreatment experts from Auburn, Michigan State, Purdue, and Texas A&M Universities; the University of California at Riverside; and the National Renewable Energy Laboratory using switchgrass provided by Ceres, Inc., and enzymes furnished by Genencor, a Danisco Division. The Office of the Biomass Program of the US Department of Energy funded this project to develop comparative data on enzymatic hydrolysis of switchgrass solids following pretreatment by leading technologies. Although various preparations of cellulase and hemicellulase have been tested for cellulose and/or hemicellulose hydrolysis, they were not tailored individually for specific cellulosic feedstocks and pretreatment technologies. In addition, although previous studies showed that performance can vary considerably among pretreatment technologies, enzyme formulations and pretreatments could be better optimized through enhancing our understanding of the interaction between the two. Thus, the objectives of this research were to (1) develop comparative sugar release data on pure cellulose and xylan by cellulases and hemicellulase enzymes used in the CAFI project to better understand enzyme specificity, (2) develop comparative sugar release data for application of these enzymes to switchgrass solids resulting from leading pretreatments, (3) measure cellulase adsorption on switchgrass processed by leading pretreatments, and (4) evaluate the relationship of the digestibility of switchgrass solids from leading pretreatments to removal of lignin, xylan, and acetyl groups and cellulase adsorption.
Support from the US Department of Energy Office of the Biomass Program (Contract DE-FG36-07GO17102) made this research possible. We thank the Biomass Refining Consortium for Applied Fundamentals and Innovation (CAFI) team of Auburn, Michigan State, Purdue, and Texas A&M Universities, the University of California at Riverside (UCR), the National Renewable Energy Laboratory, Ceres, Inc. and Genencor, a Danisco Division, for providing samples, suggestions, and other invaluable assistance for this research. We are also grateful to the Center for Environmental Research and Technology of the Bourns College of Engineering (CE-CERT) at the University of California, Riverside for providing key equipment and facilities. The authors also thank Dr. Rajeev Kumar for his internal review of this paper and helpful suggestions. The corresponding author is particularly grateful to the Ford Motor Company for funding the Chair in Environmental Engineering at the Center for Environmental Research and Technology of the Bourns College of Engineering at UCR that augments support for many projects such as this.
- Enzymatic hydrolysis
ASJC Scopus subject areas
- Environmental Engineering
- Renewable Energy, Sustainability and the Environment
- Waste Management and Disposal