Statistical optimization of cellulase production and its efficacy in hesperidin extraction from orange peel and bioethanol production from rice straw by simultaneous saccharification and fermentation

Cellulolytic enzymes are of great interest for the hydrolysis of cellulosic biomass and their demand is increasing intensely due to their potential applications in second generation bioethanol production. In this study, cellulase production from Bacillus cereus KG10 was explored and the production media and cultural conditions were optimized through Box-Behnken design. Under optimized conditions, the cellulase activity was improved to 0.51 U/mL. The purity and the molecular mass of the enzyme (55.1 kDa) were confirmed by HPLC and MOLDI-TOF MS respectively. Additionally, cellulase mediated extraction of hesperidin was performed to prove extraction efficiency by ESI-MS. Likewise, the cellulase efficiency in bioconversion of lignocellulosic biomass was also confirmed towards improving the ethanol yield. The results showed that higher amounts of reducing sugar 73.2 and 89.3 % were explored from cellulase mediated hydrolysis of rice straw than that from acidalkali mediated hydrolysis. A high ethanol yield was also achieved in media added with cellulase treated rice straw (38.1 g/L) than that of acid-alkali treated rice straw (27.4 g/L) through simultaneous saccharification and fermentation (SSF) process using cellulase from B. subtilis KG10 and Saccharomyces cerevisiae. Thus, the cellulase from B. cereus KG10 could be a potential candidate in various industrial sectors.