Comparison of the adsorption and activity of lipases from Humicola lanuginosa and Candida antarctica on solid surfaces

The adsorption of lipases from Humicola lanuginosa-the wild type (WT) and a mutant with increased hydrophobicity in the active site region-and Lipase B from Candida antarctica to solid surfaces was studied by in situ ellipsometry. In addition, the activity of the adsorbed lipase was measured in situ and from the different surface concentrations, the specific activity was calculated. Concentration and temperature dependence as well as the influence of surface wettability was studied using silica surfaces with varying degree of methylation The higher hydrophobicity of the mutant compared to the WT resulted in increased amounts adsorbed, no desorbable fraction during rinsing and absence of an initial maximum in adsorbed amount (as seen for the WT) at higher concentrations. No temperature dependence for the mutant could be observed. This was in contrast to the WT where both the plateau value of the adsorbed amount and the activity decreased with increasing temperature. The influence of surface wettability was similar for both featuring a decreased adsorbed amount and increased specific activity with increasing wettability. The amount adsorbed of the Candida lipase was significantly higher at all concentrations, compared to the other lipases, and the activity was very low, indicating adsorption with the active site region directed toward the surface. The surface wettability did not affect the activity of the Candida lipase.