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 (5-45 min 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 45 min which was able to secrete 3484.8 U/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 5505.3 U/L were predicted in medium containing 5% of olive oil, 0.69% of glucose, 0.69% of sucrose, 2.5% of maltose, yeast extract (0.7 g/L), urea (0.44 g/L), (NH4 )2 SO4 (2.44 g/L), tryptone (1.19 g/L), NaCl (1.61 g/L), CaCl2 (3.81 g/L), and ZnSO4 (1.42 g/L). A mean value of 5161.3 ± 83.3 U/L of lipolytic activity was acquired from real experiments. To sum up, the lipolytic activity of wild type strain (1720.4 U/L) increased by 3-fold after UV-induced mutagenesis and medium components optimization (5161.3 U/L).