Mutative Strain Improvement of Bacterial Soil Isolates for Enhanced Lipase Activity

Bacterial lipase isolates, B1, B3 & B4 were isolated and selected through various screening procedures for best lipase isolates. These best lipase producing isolates were subjected to the strain improvement techniques by UV radiation, microwave radiation and ethidium bromide treatment for further screening and isolation of best wild and mutant lipase producing isolates. In the results, the UV irradiation method produced the maximum number of mutant strains yielding to different exposure time intervals compared to other strain improvement techniques. However, the UV irradiation at an exposure of 30s produced the best mutant lipase producing isolate named as B3UVS30 from 11.49% survived colonies of B3, producing 24mm of clear lipolytic zone and 14.5U/ml of lipase activity subjected to agar well diffusion method and titrimetric method respectively. Similarly, microwave irradiation at an exposure of 30s produced the second best mutant lipase isolate named as B1MWS30 from 57.26% survived colonies of B1, recording 16mm lipolytic zone and 12 U/ml lipase activity subjected to agar well diffusion method and titrimetric method respectively. Conversely, ethidium bromide treatment did not produce any positive mutants and further its effect resulted in the loss of lipase activity and left distorted morphology in the cultures of B1, B3 & B4. In case of isolate B4, only UV irradiation treatment method produced 10 better lipase producing mutants, but they were unstable in the subsequent generations resulting in either reduced or lost lipase activity. So the lipase isolate B3 was subjected to 16S rDNA sequencing and subsequently identified and named this parent isolate B3 as Pseudomonas sp. SPSU B3 and its mutant B3UVS30 as Pseudomonas sp. SPSU B3UVS30. Hence this bacterial isolate and its mutant were stored and the novel isolate Pseudomonas sp. SPSU B3 is made available at national agriculturally important culture collection repository (Acc. No.: NAIMCCB-01768) for further studies in the frontiers of biotechnology as a potential bacterial lipase producing strain and for its use in commercial and academic institutions.