Biochemical properties of the alkaline lipase of Bacillus flexus XJU-1 and its detergent compatibility

Abstract

The possibility of using Bacillus flexus XJU-1 lipase in detergent preparations was studied. The enzyme was monomeric protein as confirmed by liquid chromatography-mass spectrometry and its molecular weight was 15.95 kDa. The lipase showed optimum activity at pH 10.0 and was 100% stable for 24 h at pH 10.0 and 11.0. It exhibited maximum activity at 70°C and retained more than 70% of the initial activity at 60, 70 and 80°C for 24 h. The activity was stimulated by Ca2+, Ba2+, Mg2+ and Co2+, whereas 50% of the initial activity was lost with Fe3+ and Hg2+. The activity was inhibited by 10 mM N-bromosuccinimide and tosyl-L-lysylchloromethylketone, while N-ethylmaleimide, phenylmethylsulphonylfluoride and urea did not show any effect. The enzyme significantly hydrolysed olive, cottonseed, sunflower, groundnut, and gingelly oils. With p-nitrophenyl palmitate, Vmax and Km were 62.5 U/mL and 2.25 mM, respectively. The lipase maintained its stability in Tween-80, Triton-100 and H2O2 at 1%, but an activation of 10% and a reduction of 15% in relative activity were observed with NaClO and sodium dodecyl sulphate, respectively. The enzyme retained maximum storage stability for 20 days at −20, 4 and 30°C. In the presence of 0.7% (w/v) Ariel, Henko, Super wheel, Tide plus and Rin, a retention of more than 84.90% initial activity was recorded after 24 h at 60°C. The supplementation of the lipase to the detergents improved the olive oil stain removal. These properties suggested the present enzyme as a potential additive for detergent preparations.