Statistical optimization of production conditions of β-glucosidase from Bacillus stratosphericus strain SG9

The present study illustrates the optimization and characterization of β-glucosidase from a bacterial isolate, strain SG9. Sixty-eight different variables were first screened by one factor at a time method. The screened variable optimization was then performed by Plackett–Burman design followed by Box–Behnken response surface methodology. Thirty-one variables were screened, of which five variables were found to be significant. Box–Behnken design was then performed using the most significant variables, viz., esculin, K2HPO4 and MgSO4. The maximum enzyme activity was observed with an optimal medium composition of esculin (1.9 g/L), K2HPO4 (0. 5 g/L) and MgSO4 (0.3 g/L) with a predicted value of 3392.01 IU. The maximum β-glucosidase production achieved was 3340 IU. The bacterial strain was identified by 16S rRNA gene sequence and biochemical characterization. The strain was identified as Bacillus stratosphericus and is a first report of its kind.