Overproduction of thermoalkalophilic lipase secreted by Bacillus atrophaeus FSHM2 using UV-induced mutagenesis and statistical optimization of medium components

Microbial enzymes of extremophilic origin serve as a vital source of stable industrial enzymes. The present study focused on overproduction of a thermoalkalophilic lipase produced by Bacillus atrophaeus FSHM2 through UV-induced random mutagenesis (5-45min exposure to UV light) and factorial experimental design augmented to response surface methodology. Firstly, a UV-induced mutant (designated as UV-45) was developed after the exposure of wild strain to UV irradiation for 45min which was able to secrete 3484.8U/L lipase. Afterward, Plackett-Burman experimental approach augmented to central composite design was employed to optimize medium components (olive oil, maltose, glucose, sucrose, yeast extract, tryptone, urea, (NH4)(2)SO4, NaCl, CaCl2, and ZnSO4) for lipase production by the UV-45 mutant strain. The maximum lipase production of 5505.3U/L were predicted in medium containing 5% of olive oil, 0.69% of glucose, 0.69% of sucrose, 2.5% of maltose, yeast extract (0.7g/L), urea (0.44g/L), (NH4)(2)SO4 (2.44g/L), tryptone (1.19g/L), NaCl (1.61g/L), CaCl2 (3.81g/L), and ZnSO4 (1.42g/L). A mean value of 5161.3 +/- 83.3U/L of lipolytic activity was acquired from real experiments. To sum up, the lipolytic activity of wild type strain (1720.4U/L) increased by 3-fold after UV-induced mutagenesis and medium components optimization (5161.3U/L).