Production and characterization of a milk-clotting protease in the crude enzymatic extract from the newly isolated Thermomucor indicae-seudaticae N31 : (Milk-clotting protease from the newly isolated Thermomucor indicae-seudaticae N31)

Abstract

Microbial rennet-like milk-clotting enzymes are aspartic proteinases that catalyze milk coagulation, substituting calf rennet. Crude enzymatic extract produced by the thermophilic fungus, Thermomucor indicae-seudaticae N31, on solid state fermentation (SSF) using wheat bran, exhibited high milk-clotting activity and low proteolytic activity after 24 h of fermentation. Highest milk-clotting activity (MCA) was at pH 5.7, at 70 °C and in 0.04 M CaCl 2; it was stable in the pH range 3.5–4.5 for 24 h and up to 45 °C for 1 h. MCA was highly inhibited by pepstatin A. Hydrolytic activity profile of the crude enzymatic extract on whole bovine casein, analyzed by gel electrophoresis (Urea–PAGE) and RP-HPLC revealed low proteolytic action towards casein fractions and a peptide profile similar to the one obtained with commercial Rhizomucor miehei protease (Hannilase).