Monday, April 30, 2007

Enzymatic hydrolysis of AFEX treated corn stover and Miscanthus at high solid loadings

Leonardo Sousa, Venkatesh Balan, Shishir P. S. Chundawat, and Bruce E. Dale. Department of Chemical Engineering and Material Science, Michigan State University, 2527 Engineering building, E. Lansing, MI 48824

Several process economic studies for production of lignocellulosic ethanol indicate that a minimum ethanol concentration of at least 4% (w/w) prior to distillation is required. This constraint essentially mandates that the total non-soluble lignocellulosic solids loaded for enzymatic hydrolysis be above 15% (w/w). However, enzymatic hydrolysis at higher solid loadings is significantly inhibited by several factors: (1) higher concentration of inhibitors (e.g. organic acids, furans and phenolic compounds) (2) free monomeric sugars (3) mass transfer issues.

Ammonia Fiber Expansion (AFEX) is a novel alkaline pre-treatment technology used to pretreat lignocellulosic biomass that may produce reduced inhibitor levels compared to acidic pretreatments. It is the aim of this study to understand how high non-soluble solid loadings can affect the enzymatic hydrolysis of AFEX treated corn stover and Miscanthus. In this study, corn stover and Miscanthus were pretreated using optimal AFEX conditions followed by solvent washing and enzymatic hydrolysis to improve hydrolysis yields at high solid loadings. Enzyme synergy studies were also carried out using micro plate based screening in order to determine the best enzyme combinations for each biomass material. Sugar conversions after 72h and 168h of hydrolysis were determined for a range of glucan loadings (1-12%) using best enzyme combinations in a fed batch process mode.