Enhancement of lipase stability and productivity through chemical modification and its application to latex-based polymer emulsions

Abstract

Abstract The primary focus of this research was to employ amino-group specific chemical modifications for improving the productivity and stability of two commercially produced lipases, Lipase-A from Candida antarctica (CAL UM ) and Greasex from Humicola lanuginosa (HLL UM ), for application in a latex-based paint formulation. The modified lipases showed higher percentage increase (benzoic anhydride-modified, HLL BA , 150%; PEG-modified, HLL PEG ,162% at 75 °C) as well as higher absolute productivities 41, 50, 52 and 53 μmole substrate mg −1 lipase for unmodified, CAL PEG , HLL PEG and HLL BA , respectively at 37 °C. The half-lives of thermal inactivation for all modified variants were improved from 40 to 166% at 50, 60 and 70 °C relative to unmodified lipases. The higher thermal stability and catalytic efficiency (k cat /K m ) with concomitant lower activity (k cat ) indicates that enhanced productivity is likely to be due to the modified enzymes being better able to resist thermal denaturation over the time course of the productivity experiments. Importantly, both lipases, CAL BA (60%) and HLL BA (55%) retained the highest activity in paint compared with CAL UM (36%) and HLL UM (39%) after 20 weeks incubation at 25 °C. The long term stability of the modified lipases illustrates their potential value for commercial paint and other industrial applications.