Optimization of medium components for the production of milk clotting enzyme by a filamentous fungus A26 in solid state fermentation using rice bran

Abstract

Microbial production of milk clotting enzyme by an airborne filamentous fungus A26 was studied in solid state fermentation using rice bran as a substrate. Effects of various nitrogen sources on milk clotting activity (MCA) and specific activity of milk clotting/mg protein (SPA) were investigated using a completely randomized design. The highest levels of MCA (1,467 S.U./ml) and SPA (3,861 S.U./mg protein) were obtained when ammonium sulfate was supplied to provide 0.05% nitrogen. Impacts of glucose, lactose, and ammonium sulfate on MCA were evaluated by response surface methodology. The results suggested that glucose, lactose, and ammonium sulfate enhanced MCA. Within the ranges of concentration studied, the highest MCA at 1,727 S.U./ml was predicted by the model when glucose, lactose, and ammonium sulfate were supplied at 0.040, 0.040, and 0.004 g/g rice bran, respectively