Abstract
Lipase from Thermomyces lanuginosus (TLL) has been immobilized on a methacrylate macroporous resin coated with octadecyl groups (Purolite Lifetech((R)(R)) ECR8806F). This immobilization protocol gave a biocatalyst with significantly higher stability than that obtained using octyl agarose. To further improve the biocatalyst features, we tried to covalently immobilize the enzyme using this support. For this purpose, the support was activated with divinyl sulfone. The results showed that at least 1/3 of the immobilized enzyme molecules were not covalently immobilized. To solve the problem, we produced an aminated support and then activated it with divinyl sulfone. This permitted the full covalent immobilization of the previously immobilized TLL. The use of different blocking agents as the reaction endpoint (using ethylenediamine, Asp, Gly, and Cys) greatly altered the biocatalyst functional features (activity, specificity, or stability). For example, the blocking with ethylenediamine increased the ratio of the activity versus R- and S-methyl mandelate by a three-fold factor. The blocking with Cys produced the most stable biocatalyst, maintaining close to 90% of the activity under conditions where the just adsorbed enzyme maintained less than 55%. That way, this strategy to modify the support has permitted obtaining an enzyme interfacially activated versus the octadecyl layer and, later, covalently immobilized by reaction with the vinyl sulfone groups.