Abstract

The purpose of the present investigation is to enhance production of the biomedically important enzyme, lipase, by subjecting the indigenous lipase producing fungal strain Aspergillus japonicus MTCC 1975 to strain improvement and random mutagenesis (UV irradiation, HNO₂ and N-methyl-N’-nitro-N-nitroso guanidine). The isolation of mutants and the lipolytic activity of selected mutants were described. The best UV selectant (AUV₃) showed 127% higher lipase activity than the parent strain. The lipase yield of the best HNO₂ mutant (AHN₃) was 139% higher than UV mutant (AUV₃) and 177% higher than the parent strain. Also, the lipase yield of the best NTG mutant (ANT₄) was 156% higher lipase activity than the HNO₂ mutant (AHN₃) and 217% higher than the UV mutant (AUV₃) and 276% higher lipase activity than the parent strain. The results indicated that UV, HNO₂ and NTG treatment were effective physical and chemical mutagenic agents for strain improvement of Aspergillus japonicus for enhanced lipase productivity.

Key words: Lipase, Aspergillus japonicus, UV Irradiation, HNO₂ and N-methyl-N’-nitro-N-nitroso guanidine.