Isolation, Screening and Optimization of Lipase Producing Fungal Strains from Agricultural Soil

Abstract

Potent fungal lipase producers have been isolated from paddy field of agricultural soil was studied in submerged batch fermentation. Total 14 fungal isolates were obtained by using serial dilution technique. Preliminary qualitative screening was done by using Tributyrin agar medium for the secretion of lipase from fungal isolates. Six fungal isolates out of the 14 isolates were shown clear holo zone in TBA plates after 3-7 days of incubation. Quantitative screening was done for the production lipase; shake-flask culture method has been used. In present investigation for the modification of culture condition and nutrient source it have been optimized by involving various parameters such as pH, time course, inoculum volume, agitation rate as well as various substrates were evaluated in this study. Lipase was detected in culture filtrate by using filtration technique. From the results, revealed that the isolated fungal cultures are alkaline in nature as because of the medium pH of 8.0 and temperature range of 35°C when incubated up to 96 hours in 3 ml of inoculum volume and 150 rpm agitation rate were optimum for maximizing lipase production under submerged fermentation by fungal isolates i.e. mostly of belongs to genera Aspergillus sp. Under Submerged fermentation the mineral growth medium (MGM) contained (in g/L) NaH2PO4: 12.0, KH2PO4: 2.0, MgSO4.7H2O: 0.3 and CaCl2: 0.25. Ammonium Sulphate at 1% and mustard oil - 2% were used as carbon and nitrogen source respectively. Highest Lipase activity were obtained from CAK7 (Aspergillus tamarii) and CAK9 (Aspergillus niger). Maximum lipase activity 88.74 U/ml obtained by Aspergillus niger sp. followed a logarithmic pattern on the 4th day of fermentation. By using Statistical approach (OFAT) revealed that the culture conditions significantly (p<0.05) influenced lipase production by these fungal isolates. In this investigation results obtained for the production of extracellular lipase under submerged fermentation mustard oil could be used as a substrate inducer would be economically cost effective and beneficial for industrial applications