Enhancement of Extracellular Lipase Production by Strain Improvement of Fungus Aspergillus niger LPF-5

Twelve fungal isolates belonging to different genera were quantitatively screened for extracellular lipase production in SmF (Submerged fermentation). Isolate LPF-5 demonstrated higher lipase activity and it was identified as Aspergillus niger based on morphology of its Petri plate culture, microscopic study of its slide culture and with the help of relevant literatures. Further an effort was made to increase the production of extracellular lipase by subjecting the most potent lipolytic fungal strain A. niger LPF-5 to the strain improvement by induced mutagenesis using UV radiations and nitrous acid. Among the all tested mutagens, nitrous acid was found to be the best mutagen (incubation time of 15 minutes) for inducing the favorable mutation in fungal strain A. niger LPF-5 which enhanced the lipase activity up to 30% (105.19 ± 0.91 U mL -1 min -1 ) when compared to lipase activity (81.00 ± 0.30 U mL -1 min -1 ) of wild strain while the lipase activity of the best UV mutant (A. niger UV3), obtained after an incubation of 6 minutes was 94.30 ± 0.54 U mL -1 min -1 , which was 16.41% higher as compared to wild strain of A. niger. These results indicate that UV light and nitrous acid both were effective mutagens but nitrous acid was more potent mutagen than UV light.