Establishment of physical environment in solid state fermentation for the production of glucoamylase using Box-Behnken design

Aims: Glucoamylase is an industrially important enzyme and is second to the proteases in worldwide distribution and sales among industrial enzymes. The aim of this study was to maximize its production from a GRAS strain Aspergillus oryzae IIB-6 using cheap medium by solid state fermentation. Methodology and results: Different carbon and nitrogen sources were evaluated as an additional supplement to wheat bran. The response surface methodology (RSM) was employed for optimization of most important physical parameters viz., pH, temperature and inoculum density as their monitoring is very difficult because of the solid nature of the substrate. Box-Behnken factorial design based on three levels and three variables was employed to obtain optimal combination of three independent variables. Maltose and peptone were found to be the best additional carbon and nitrogen sources. The optimal conditions for pH, temperature and inoculum size were 5.29, 36.2 °C and 17.7% (v/w), respectively as prescribed by second-order polynomial quadratic model. Under optimized conditions, the experimental value of enzyme activity was 7750.02 U/gds, which is very close to 7713.04 U/gds predicted by the model. R2 was 99.99% which indicates a good agreement between experimental and predicted values. Conclusion, significance and impact of study: The analysis of variance showed that p-values of the coefficients for linear effects and square effects of all the variables were 0.0001, suggesting these variables are highly significant for the enzyme production. Overall 23.01% increase in enzyme production was achieved by RSM optimization which can be proposed for food and pharmaceutical industries.