Characterization of Free and Immobilized Thermomyces lanuginosus Lipase for Use in Transesterification Reactions

Abstract

Thermomyces lanuginosus lipase, in both its free form as well as immobilized in sol-gel matrices produced using the precursor tetraethoxysilane (TEOS) and dried using the xerogel technique, was used in transesterification reactions between 2-phenylethyl alcohol and vinyl acetate. The free lipase was first characterized in terms of its transesterification activity at 37°C, with a value of 1,233 U/g obtained and lower temperatures providing higher activity. The influence of humidity on the enzyme immobilized with TEOS was evaluated using a 2² factorial design (varying the conditions of humidity and temperature). The results indicate that higher humidity (30%) and lower temperature (40°C) provided the best transesterification activity, and that these two factors and their interaction had a significant influence on activity (at the 95% confidence level). Under these conditions, the biocatalyst presented a surface area of 502 m²/g, a pore volume of 0.643 cm³/g, and an average pore diameter of 51.2 Å. These results reflect its effectiveness in this type of reaction. Differences between the support alone and the immobilized biocatalyst were observed using scanning electron microscopy.