(573a) Pretreatment of Rice Straw with Ammonia Recycled Percolation

Because of high contents of cellulose (~37 wt%) and hemicellulose (~17%), rice straw seems to be a potential lignocellulosic biomass for production of bioethanol. In this study, Ammonia Recycled Percolation (ARP) pretreatment of rice straw was extensively investigated. In particular, the experimental study included the effects of temperature, reaction time and concentration of ammonia on compositions and enzymatic digestibility of the resulting solid residues; the ranges of pretreatment conditions were, in turn, 150°C~210°C, 10 min ~ 90 min and 0~ 20 wt%. Through ARP pretreatment, the lignin content was reduced by as high as ~84% while 20~80 % of the hemicellulose was solubilized. The solid residue resulted from the pretreatment with 15 wt% aqueous ammonia solution at 170°C for 90 mim showed as high as ~90% of digestibility with enzyme loading of 15FPU/g of glucan. Addition of the xylanese along with cellulase led to a notable enhancement of digestibility, indicating a possible inhibitory role of hemicellulose. Simultaneous Saccharification and Fermentation (SSF) and Simultaneous Saccharification and Co-Fermentation (SSCF) were performed to obtain ethanol productions of 1.38 g/L (corresponding to 81% yield) and 15 g/L (corresponding to 89% yield), respectively.