Improvement of lipase stability in the presence of commercial triglycerides

Abstract

Several compounds generated by atmospheric oxidation of triglycerides, such as hydroperoxides and secondary products, may cause significant lipase inactivation in low-water medium. Activity decay is usually time-dependent and shows a non-linear dependence on inactivating compound concentration. As the effect of very dilute poisons becomes much more significant in continuous operations, stability tests were performed in the presence of oxidized oils in batch and continuous reactors. Experimental results show that the stability of Novozyme 435 is affected by secondary products of oxidation more than by hydroperoxides. Involvement of sulphydryl groups in the mechanism of lipase interaction with two aldehydes, 4-hydroxynonenal (4-HNE) and malondialdehyde (MDA), has been demonstrated by blocking the lipase sulphydryl groups with pHMB pre-treatment. The preliminary neutralization 4-HNE and MDA with albumin also increased enzyme stability.