Effect of Ca2+ Ion to the Activity and Stability of Lipase Isolated from Chromohalobacter japonicus BK-AB18

Lipase extracellularly produced by Chromohalobacter japonicus BK-AB18 (lipase BK-AB 18) have been isolated and fractionated with 60-70% ammonium sulfate Native PAGE and zymography analysis revealed a single 37 kDa lipase exist in this fraction This enzyme exhibited optimum activity at 45 °C and pH 9.5 The addition of various metallic ions affected the activity of lipase BK-AB 18 and among them, Ca2+ ion was the most prominent in enhancing its activity In the presence of Ca2+ ion, themostability of the enzyme was improved as showed by the relatively high residual activity at 85 oC The optimum pH in the presence of this ion turn into a wider range instead of a single value, which was from pH 7.5 to 9.5 The enzyme also became stable against nonpolar organic solvent (n-hexane), detergent (5 mM SDS) and hypersaline solution (8% NaCl solution) The addition of Ca2+ ion, therefore, have turned lipase BK-AB18 into a multistable enzyme, which is potential to be further developed for various industrial applications, particularly those industries operate their process in harsh conditions, such as high temperature, high salinity and involving organic solvent or surfactant.