Mutation induced enhanced biosynthesis of lipases by Rhizopus oligosporus var. microsporus

摘要

The present study describes the isolation, identification and screening of fugal strain Rhizopus oligosporus (var. microsporus) for the production of extracellular lipases. One hundred and sixty seven cultures of fungi were isolated from different environments such as soil, air, milk, pickle, oily bread, decayed fruits and vegetables by serial dilution method. The strains were initially selected qualitatively on Tween 80-Agar plates and were shifted to the slants of PDA for maintenance and storage at 4oC. Quantitative screening for extracellular lipase production by isolated strains was carried out in shake flasks and the most potent strain producing 3.20 ± 0.003 U mL-1of enzyme was selected. The strain was then identified on the basis of standard morphological measurements and was assigned the code IIB-63. The selected strain was then subjected to physical (UV and Gamma radiations) and chemical mutagenic (MNNG/NTG, NA, EtBr) treatments in order to improve its lipolytic potential. During the treatment, mutants were qualitatively and quantitatively selected and IIB-63NTG-7was found to be the mutant showing highest lipases production (10.37 ± 0.06a U mL-1) with a zone size of 12.3 mm on Luria-Bertani-tributyrin agar plates. This mutant showed an overall 325% increase in activity over its parent strain for the production of extracellular lipase.