Enhanced saccharification of rice straw and hull by microwave–alkali pretreatment and lignocellulolytic enzyme production

Abstract

In this study, statistical design of experiments was employed to plan experiments and optimize the microwave-alkali pretreatment of rice straw and hulls. Process parameters important in pretreatment of biomass were identified by a Plackett-Burman design and the parameters with significant effects were optimized using a box-behnken design (BBD). Experimental results show that alkali concentration (AC), irradiation time (IT) and substrate concentration (SC) were main factors governing the saccharification of rice straw and hulls. Optimum conditions of pretreatment were AC 2.75%, IT 22.50 min and SC 30 g/L, as optimized by BBD. The growth and production of lignocellulolytic enzymes from Aspergillus heteromorphus, solid state fermentation (SSF) was performed using rice straw and hulls pretreated under optimum conditions. Cellulases and xylanase reached the highest enzyme activity at 6th day of fermentation while maximum manganese peroxidase (MnP) and laccase activity occurred at 12th day.