Production of Milk Clotting Enzyme from Aspergillus oryzae under Solid-State Fermentation using Mixture of Wheat Bran and Rice Bran

Microbial rennet-like milk-clotting enzymes are aspartic proteinases that catalyze milk coagulation, substituting calf rennet. Crude enzymatic extract produced by the Aspergillus oryzae NCIM 1032, on solid state fermentation (SSF) using mixture of wheat bran and rice bran (7:3), exhibited high milkclotting activity (MCA) and low proteolytic activity (PA) after 120 h of fermentation. Highest milk-clotting activity was at pH 7.5, at 30 oC. Glycerol (5%) was found to be best solvent for leaching out milk clotting enzyme. The yield of enzyme was improved with the supplementation of glucose and beef extract as a carbon and nitrogen source respectively. Metabolic heat generated due to fermentation was equally distributed throughout the substrate bed by agitation in rotating drum bioreactor and enzyme production increased at speed of 25 rpm and at intermittent agitation (1 min/day). High ratio of milk clotting to proteolytic activity strengthens the potential usefulness of milkclotting enzyme of Aspergillus oryzae NCIM 1032 as a substitute for calf rennet in cheese manufacturing.