Combination of hot compressed water treatment and wet disk milling for high sugar recovery yield in enzymatic hydrolysis of rice straw

Abstract

Rice straw has attracted significant interest in Japan as a potential raw material for biorefineries. Combination of hot-compressed water treatment (HCWT) and wet disk milling (WDM) was investigated to improve the enzymatic digestibility of rice straw and enhance sugar recovery yield. Rice straw, cut to <3mm, was autoclaved at 121, 135, and 150°C for 60min, and subsequently treated by wet disk milling. WDM with HCWT at 135°C for 60min produced maximum xylose and glucose yields of 79% and 90%, respectively, at 10FPU/g-substrate cellulase loading. Autoclaving at 150°C leaked a 35% arabinose effluence in the liquid phase. Hydrolysis via WDM with HCWT required a lower enzyme loading (5FPU/g-substrate) than either pretreatment process in isolation for >70% xylose and 80% glucose yield. Economical analysis indicate that enzymes cost for ethanol production is reduced by 19–67% by WDM with HCWT.