Abstract
The object of this study was to optimize the aqueous ammonia pretreatment of rice straw for maximum sugar yields by enzymatic hydrolysis, with respect to ammonia concentration, liquid-to-solid ratio, temperature, time, and particle size. The experiment was based on uniform design, the enzymatic digestibility of pretreated rice straw varied from 21.2 % to 74.2 %, and the ratio of delignification varied from 12.2 % to 80.9 % at different experiment conditions according to uniform design. The optimum pretreatment conditions for sugar yields from rice straw were 170 ℃, 23 % ammonia water, and a solid-to-liquid ratio of 1:25. At this optimum condition, 56 % removal of lignin was obtained and the enzymatic digestibility increased to 87 % with the enzyme loading of 15 FPU/g-glucan. The results of multiple regression analysis indicated that the concentration of ammonia had the most significant effect on the sugar yield. The significance of parameters that affected sugar yield was ranked in the following order: CN (Ammonia concentration) > Tm (temperature) > VN (liquid-to-solid ration) > t (Reaction time) > d (Particle size).
