Optimization of microbial milk clotting enzyme production by Aspergillus candidus MTCC1989 using statistical method

Abstract

Microbial milk clotting enzymes have been highly valued as calf rennet substitutes in the cheese industry. The present study was aimed to optimize the fermentation media components for the production of milk clotting enzyme by Aspergillus candidus MTCC 1989. A 5-level central composite design of response surface methodology was employed to optimize the fermentation media components namely yeast extract, skimmed milk powder, potassium di-hydrogen phosphate and initial pH. The various effects of media components on milk clotting enzyme production were fit into second order polynomial model and statistically analysed using student’s t-test and Fisher’s F-test for analysis of variance. The high value coefficient of determination (R2=0.89) justified an excellent correlation between media components and milk clotting enzyme production, and the model fitted well with high statistical reliability and significance. The optimal concentration were yeast extract 1.5% (w/v), skimmed milk powder 0.87% (w/v), potassium di-hydrogen phosphate 0.11% (w/v) and an initial pH 6.1. The 774.19 MCU of milk clotting enzyme was obtained by A. candidus at the optimal conditions.