Isolation, Identification of Aspergillus Niger and Optimization of Extracellular Lipase Production

Abstract

Seven different fungal strains were isolated from various sites on the campus of Stella Maris College (Autonomous), Chennai and identified as Aspergillus niger, Aspergillus flavus, Aspergillus fumigatus, Pencillium citrinum, Mucor racemosun, Cladosporium cladosporoides, Rhizopus stolonifer apart from some sterile hyphae. The fungal isolates were tested for lipase production. It was found that Aspergillus niger showed better zone for lipase enzyme. 15g of Groundnut was found to be ideal for extra cellular lipase production by A. niger (509 U/g). Glucose as a carbon source (602 U/g) and Ammonium nitrate was used as the nitrogen source (579 U/g) showed the maximum enzyme production.  Olive was an excellent substance (579 U/g) and production of the enzyme enhanced between temperatures of 40ºC (534 U/g) - 45ºC (579 U/g). The optimum pH was 6.5(681 U/g). The maximum protein content was found to be at 4 ºC (114 µg) and pH 6.5 (122 µg). Maximum zone of hydrolysis (4mm) was observed at 15g as substrate concentration while it was 5mm when dextrose was used as the carbon source. When Potassium Nitrate was used as the nitrogen source the zone of hydrolysis was 4mm. A maximum zone of was observed for olive oil and gingely oils. The maximum zone of hydrolysis was 3mm at 28 and 37 ºC and 5mm at pH 6.5. SDS PAGE analysis of the crude lipase enzyme showed the presence of a prominent protein band of 40KDa apart from some other proteins of lower molecular weight.