Monday, April 30, 2007

Improvements in glucan conversion in rice straw while producing valuable isolates using solid state fermentation and the AFEX process

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

Rice straw is an important lignocellulosic biomass, with nearly 800 million dry tons produced annually worldwide.  Being an agricultural waste product, rice straw has great potential for making renewable fuels, ruminant feed, and also for extracting silica.  Compared to AFEX treated corn stover (95% glucan conversion), AFEX treated rice straw has a lower sugar conversion (75% glucan conversion) during enzymatic hydrolysis, for optimal pretreatment conditions. In order to increase the glucan conversion, we employ solid state fermentation (SSF) using Pleurotus ostreatus as an additional pretreatment prior to AFEX.  SSF followed by AFEX (Bio-AFEX) increases glucan conversion by 20% (providing 95% conversion), making Bio-AFEX treated rice straw attractive for cellulosic ethanol production. In conjunction, treatment with P. ostreatus produces valuable byproducts like mushrooms, organic acids and proteins. Rice straw contains approximately 10% silica and its extraction from enzymatic hydrolysate solids provides another potentially useful commodity from this biomass. In this presentation we will provide quantitative information about various products formed and a complete mass balance for AFEX pretreatment, enzymatic hydrolysis and silica extraction for SSF treated rice straw.