Parametric Optimization of Cultural Conditions for Carboxymethyl Cellulase Production Using Pretreated Rice Straw by Bacillus sp. 313SI under Stationary and Shaking Conditions

Carboxymethyl cellulase (CMCase) provides a key opportunity for achieving tremendous benefits of utilizing rice straw as cellulosic biomass. Out of total 80 microbial isolates from different ecological niches one bacterial strain, identified as Bacillus sp. 313SI, was selected for CMCase production under stationary as well as shaking conditions of growth. During two-stage pretreatment, rice straw was first treated with 0.5 M KOH to remove lignin followed by treatment with 0.1 N H2SO4 for removal of hemicellulose. The maximum carboxymethyl cellulase activity of 3.08 U/mL was obtained using 1% (w/v) pretreated rice straw with 1% (v/v) inoculum, pH 8.0 at 35°C after 60 h of growth under stationary conditions, while the same was obtained as 4.15 U/mL using 0.75% (w/v) pretreated substrate with 0.4% (v/v) inoculum, pH 8.0 at 30°C, under shaking conditions of growth for 48 h. For maximum titre of CMCase carboxymethyl cellulose was optimized as the best carbon source under both cultural conditions while ammonium sulphate and ammonium nitrate were optimized as the best nitrogen sources under stationary and shaking conditions, respectively. The present study provides the useful data about the optimized conditions for CMCase production by Bacillus sp. 313SI from pretreated rice straw.