Mutagenesis by UV and Nitrous Acid for increase of rennet production in Rhizomucor miehei

In this study, Mutation and Selection technique was used to increase production of Rennet (milk clotting enzyme) in Rhizomucor miehei. Mutation and Selection is a technique for microbial strain improvement in which, mutation is induced on an organism by mutagen factors, then superior mutants are selected by screening procedures. Mutations were induced by an optimized dose of UV (as physical mutagen) and Nitrous acid (as chemical mutagen). Superior mutants were selected and compared to the parent strain regarding the clotting activity, proteolytic activity, enzyme production kinetic, yield, productivity and special growth rate in 5 replications. The milk clotting activity of parent strain was 1183 SU.mL-1. Mutants designated U-1113 and N-0227 were isolated which, produced 1771 and 1864 respectively. ratio was measured 4950, 8114 and 8193 SU.PU-1 in parent, U-1113 and N-0227, respectively. Discussion and Production of enzymes in mutants U-1113 and N-0227 were increased 49.7 and 57.6% respectively, relative to parent strain. Yield of production, productivity and C/P ratio were also increased significantly in mutants, regarding the same figures obtained for parent (p<0.05) that shows mutagens were used, have effected on quantity and quality of strain rennet.