Statistical optimization of xylanase and alkaline protease co-production by Bacillus spp using Box-Behnken Design under submerged fermentation using wheat bran as a substrate

This study explores the co-production of xylanase and alkaline protease from Bacillus licheniformis NRRL 14209 in single step using agricultural waste as a substrate. The aim of the present study was to screen the low cost and easily available agricultural lignocellulosic wastes as a substrate to substitute commercially available xylan. Five agricultural wastes were screened as a substrate and wheat bran was found to be most suitable for co-production of xylanase and alkaline protease. Optimization of various fermentation parameters affecting enzyme co-production by B. licheniformis was investigated. Maximum enzyme productivity of xylanase 4.31 U/mL and alkaline protease 3.66 U/mL was obtained at 24 h of incubation period, initial media pH 8.5 with 0.5% w/v wheat bran and 4% (v/v) inoculum concentration at 30 degrees C temperature. Box-Behnken Design was applied to obtain optimal concentrations of significant variables such as substrate concentration (0.25% w/v), inoculum concentration (4% v/v) and pH of 7.5. The maximum xylanase and alkaline protease production after Box-Behnken Design was 5.49 U/mL and 4.87 U/mL respectively, which are 1.27 and 1.33 fold higher than initial one factor at a time media optimization. Xylanase and alkaline protease isolated in this study can be useful in pulp pre-bleaching process to remove the hemicelluloses and in detergent industry respectively.