Abstract

Lipases (triacyl glycerol acyl hydrolase) catalyze hydrolysis and syntheses of ester formed from glycerol and long-chain fatty acids. They have many industrial applications, especially in food and detergent industries. Out of 33 bacterial isolates, a group of 20 bacterial isolates produced lipase enzyme on tributyrin agar and Tween 80 agar media. In liquid medium, the lipase activity was ranged from 1.5 to 6.9 IU/ml. Among the evaluated bacteria, the isolate LP10 that was isolated from soil collected from fuel station. It was the most active isolate in lipase production (6.9 IU/ml). Using morphological, physiological and biochemical studies, it was identified as an isolate belonging to the genus Streptomycesand identified as Streptomyces exfoliates LP10. Identification was confirmed using 16S rDNA analysis. Growth of the selected bacterium in medium containing tributyrin and Tween 60 at initial pH 6 in addition to incubation at 37°C for three days yielded the maximum lipase production. The molecular weight of the purified enzyme was 60 kDa, determined using gel electrophoresis. Improvement of lipase production was carried out between Streptomyces exfoliates LP10 and Streptomyces niveus using protoplast fusion. Five fusants were obtained. Fusant LP3 was the best lipase producer (3 times higher) compared to its parents.

Key words: Lipase, Streptomyces exfoliates, tributyrin, protoplast fusion, 16S rDNA.