Determination of immobilized lipase stability depends on the substrate and activity determination condition: Stress inactivations and optimal temperature as biocatalysts stability indicators

Abstract

Lipases A and B from Candida antarctica (CALA and CALB), Thermomyces lanuginosus (TLL) and Candida rugosa have been immobilized on octyl, octyl-vinyl sulfone (blocked with ethylendiamine) and amino-glutaraldehyde. The biocatalysts exhibited different specificity versus triacetin and p-nitro phenyl butyrate. Optimal activities were determined using triacetin for all biocatalysts, and this ranged from 40 °C for CALA and TLL, to 60 °C for an amino-glutaraldehyde-CRL. The biocatalysts were inactivated at 70 and 75 °C, determining their residual activities at 25 °C or 55 °C. The inactivation courses were very different depending on the substrate; in most cases the biocatalysts maintained more activity during the thermal inactivation using triacetin (except using TLL). When determining the residual activities at 55 °C, the values increased in most cases, reaching high hyperactivation values using CALA (even 23 folds). That way, the “stability” of the different preparations was strongly influenced by the substrate and residual activity determination conditions, and did not agree in most cases with the optimal temperatures.