XPS studies of the cellulase adsorption on particulate celluloses

摘要

In heterogeneous biocatalysis, the substrate effective concentration is proportional to theaçcessible surface area. In previous work, this area was measured with the help of BSAadsorption isotherms. In this work, it is shown that the affinity in the BSA adsorption oncellulose does not depend on the cellulose crystallinity, since the concentration of BSA on different cellulose surfaces is similar, as measured by the XPS determination of thenitrogen content.lt is shown that the cellulolytic enzymes are able to adsorb two to three times more thanthe BSA molecule does at the saturation level, which means that the cellulases adsorbeither in multilayers or in a more organized (compacted) way than the BSA. Finally, it isshown that the surfactant Tween 85 is able to reduce the amourit of adsorbed enzymes i when the bulk enzyme concentration is relatively low, which correlates with a higherenzyme activity. When the enzyme concentration is raised, both the adsorbed enzyme concentration and the enzyme activity remain unaffected by the surfactant. This seems tosupport the hypothesis that the surfactant helps the enzyme by enabling the sequence oftvents adsorption-desorption,