The effects of aqueous ammonia-pretreated rice straw as solid substrate on laccase production by solid-state fermentation.

Chemical composition and physical structure of solid substrate have significantly impacts on fermentation performance. The aqueous ammonia was used to pretreat rice straw. Furthermore, the feasibility of pretreatment to improve laccase production was also evaluated in terms of the enzymatic digestibility, chemical structure, physical structure, and laccase production. The results showed that aqueous ammonia pretreatment could modify chemical compositions, destroy rigid structure of the lignocellulosic substrate, increase enzymatic digestibility and change water state, which were beneficial to facilitate the fungus growth and nutrition utilization. Pretreatment of lignocellulosic substrate with aqueous ammonia at 80 °C gave the best effect on laccase production, yielding 172.74 U/g laccase at 14 days, which was 3.4 times higher than that of the control. The aqueous ammonia pretreatment could alternate the physicochemical characteristics of lignocellulosic substrate, resulting in the improved laccase production, which was a promising method that might be explored in solid-state fermentation.