Valorization of Rice Straw for Optimization of Production of Thermotolerant Cellulase by Parageobacillus Thermoglucosidasius NBCB1 Under Submerged Fermentation

Abstract

Rice straw can be a substrate for production of cellulolytic enzymes, a vital step in economical deconstruction of cellulosic biomass in industry. We herein report the optimization of cellulase production by the thermotolerant Parageobacillus thermoglucosidasius NBCB1, in rice straw based submerged fermentation. Optimization of process parameters by One Factor At a Time (OFAT) suggested Day 3, medium pH 5.5, 1% (v/v) sorbitol, 1% (v/v) peptone and a cultivation temperature of 60°C as the optimal conditions for cellulase production. Further optimization of effective variables: incubation period, medium pH, sorbitol and peptone concentrations, by Response Surface Methodology (RSM) and Artificial Neural Networking (ANN) improved cellulase yield to 3.106 ± 0.005EU and 3.488 ± 0.004 EU/mg protein, respectively, which were closer to model diagnosed values. OFAT, RSM and ANN improved cellulase production by ~ 6.66, ~ 9.34 and ~ 10 folds, respectively, compared with enzyme production in unoptimized medium, indicating the later two being equally effective in the maximization of cellulase production. Purified cellulase (MW 31 kDa) with pH and temperature optima of 5.5 and 60°C, respectively, retained 100% activity upon pre-incubation at 60°C indicating it’s thermostability. It also showed halotolerance and heavy metal tolerance properties. Due to it’s versatile nature, the cellulase produced by P. thermoglucosidasius NBCB1 could be suitable for industrial degradation of agroresidues.