Optimization of the alpha amylase production from Bacillus amyloliquefaciens IIB-14 via parameter significance analysis and response surface methodology

In this article, we report the optimization of bacterial extracellular alpha amylase production from Bacillus amyloliquefaciens IIB-14, a locally isolated bacterial culture, using response surface methodology (RSM). Different agricultural by-products were evaluated for enzyme activity under solid state fermentation (SSF). Of those, wheat bran (10 g) was found to be optimal when moistened with 0.02 M phosphate buffer at a level of 1:1.25. A marked improvement in enzyme productivity (52.06 U/mg/min) was observed at 72 h after the cultivation at 40°C (pH 7.2). The pre-grown bacterial inoculum (24 h old) was used at a level of 20%, v/v. The combined effect of cultural and nutritional variables on bacterial amylase was further investigated using RSM. The procedure limited the number of actual experiments performed while allowing for possible interactions between the optimal components including temperature, pH and inoculum. No previous work has used statistical analysis in determining the interactions among these parameters for alpha amylase production. The p-value of the coefficient for quadratic effect was 0.002, suggesting that this was the principal experimental variable having maximal effect on enzyme productivity. The results are economically significant (p ≤ 0.05) and marked the commercial utility of the isolated bacterial culture.