Sunday, May 3, 2009
3-25
Enzymatic hydrolysis and ethanol production from AFEX pretreated bagasse at high solid loading using recombinant ethanologens
Chandraraj Krishnan1, Venkatesh Balan2, Derek Marshall2, and Bruce E. Dale2. (1) Department of Biotechnology, Indian Institute of Technology Madras, Bhupat and Jyoti Mehta School of Biosciences Building, Chennai, India, (2) Chemical Engineering and Materials Science, Michigan State University, 3900 Collins Rd, Lansing, MI 48910
Several million tons of sugarcane baggase and cane leaf matter are produced worldwide. These have a tremendous potential as sustainable lignocellulosic feedstocks for cellulosic ethanol biorefinery. The ethanol yield depends on the efficiency of conversion of glucans and xylans to fermentable sugars using pretreatment and enzymatic hydrolysis without generating byproducts that are toxic to fermentative microorganisms. Ammonia fiber expansion (AFEX) is a promising pretreatment method operates at milder conditions and does not degrade polysaccharides. The ammonia used in the AFEX process can be recovered and reused. In this work, the sugarcane bagasse and cane leaf matter were pretreated independently by AFEX under different conditions and hydrolyzed by a mixture of cellulase, xylanase and b-glucosidase enzymes. The best pretreatment conditions were identified based on higher glucan/xylan conversion during enzymatic hydrolysis. Using this optimized conditions larger batch of pretreated bagasse and cane leaf matter were hydrolyzed at high solid loading (up to 24%). Further, the hydrolyzate of both bagasse and cane leaf matter were fermented to ethanol using different recombinant ethanologenic strains of yeast and bacteria. For the ethanol fermentation process, the hydrolyzate was used as the sole carbon source with out any external nutrient or mineral supplementation. The kinetics of sugar consumption and ethanol production for different fermentation process are discussed.