Optimization of enzymatic hydrolysis of lignocellulosic biomass

Vandana Rana

Enzyme cost and hydrolytic efficiency are two crucial parameters when selecting enzymes for depolymerization of lignocellulosic biomass. Although a myriad of research efforts have been made by commercial companies and research institutions to find ways to produce enzymes with high hydrolytic efficiency at minimal production cost, there is still a lack of information on how to produce a low-cost enzyme mixture with high activity. A key challenge for use of these enzymes is the lack of optimization of amount of enzyme needed and for finding ways to produce cheaper enzymes on-site. This thesis has been divided into two sections with the overall objective of achieving a highly efficient enzymatic hydrolysis process at minimal cost. The first section includes optimization studies based on statistical modeling and experimental data were fit to the model to obtain optimal parameters for enzymatic hydrolysis of Corn stover and Douglas fir. In the first part of section I, enzymatic hydrolysis of corn stover was optimized with respect to substrate concentration and cellulase loading. Economic analysis was performed to support the findings. In the second part of section I, the minimal amount of cellulase and hemicellulase for efficient conversion of woody biomass, Douglas fir, is tested. A statistical model was used to optimize the yield of monomeric sugars. The second section is the description of on-site production of cellulolytic enzymes from mesophilic fungi using inexpensive side stream of a biorefinery. In first part of section II, enzyme cocktail were prepared from Trichoderma reesei Rut-C30 and Aspergillus saccharolyticus. Hydrolytic efficiency of on-site produced enzyme preparation for hydrolyzing Corn stover and Loblolly pine was compared with the commercial cellulase formulation, Celluclast 1.5L and Novozym 188. In the second part of section II, ethanol production from both simultaneous saccharification and fermentation (SSF) and separate hydrolysis and fermentation (SHF) were compared using on-site produced enzyme cocktail. Third part of section II focused on finding the best enzyme formulation by supplementing on-site produced enzymes with different commercial enzymes (Cellic®Ctec2, Cellic®Htec2 and Novozym 188) to enhance the activity on-site produced enzymes. This production and optimization study has potential for commercial application.

Optimization of enzymatic hydrolysis of lignocellulosic biomass

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