Raising the enzymatic performance of lipase and protease in the synthesis of sugar fatty acid esters, by combined ionic exchange - hydrophobic immobilization process on aminopropyl silica support

A sustainable industrial application of the enzymes requires their reuse and stability. These objectives are accomplished here for the Thermomyces lanuginosus lipase and Bacillus subtilis protease, by immobilization in porous silica modified with (3-aminopropyl) triethoxysilane. This silylation leaves aminopropyl groups on the silica surface, leading to a heterofunctional support, with amine and alkyl entities that participate in ionic exchange-hydrophobic interactions, respectively, with the enzyme. In this work, the silica surface is effectively modified, as it is shown by FTIR and Si-29-and C-13-ssNMR spectroscopic techniques. The characteristics of the support surface explain the changes of the catalytic properties of the two immobilized enzymes. This support promotes the homogeneous orientation and stabilization of the enzyme during the one-pot immobilization process, without the costs of other heterofunctiontal materials obtained by multiple functionalization steps. Both immobilized enzymes show thermal stabilization in aqueous solution (25mM sodium phosphate buffer, pH 7.0) at 60 degrees C and in 100% acetone at 40 degrees C, without addition of stabilizers. Both biocatalysts exhibit high performance on the synthesis of sugar fatty acid esters, in comparison with others, reported under similar reaction conditions. Due to the characteristic of the lipase/aminopropyl silica and protease/aminopropyl silica biocatalysts, they are promisors in applications that need high mechanical and enzymatic stability.