Lipase B of <i>Candida antarctica</i> co-adsorbed with polyols onto TiO₂ nanoparticles for improved biocatalytic performance

Abstract

<b>Background</b>: The immobilization of the lipase B of <i>Candida antarctica</i> CALB over TiO₂ nanoparticles was thoroughly investigated with the isotherms of adsorption at various temperatures with and without the addition of sorbitol and glycerol. The surface composition, secondary structure and the effect of the addition of the polyols was addressed. <b>Results</b>: The maximum dispersion limit of protein on TiO₂ nanoparticles (NPs) is 0.073 ± 0.007 µmol m⁻². Glycerol and sorbitol co‐adsorb on the TiO₂ NPs reaching 45% of the surface composition of the biocatalyst. The optimized material was able to catalyze the esterification of 52% of R/S‐ibuprofen with ethanol (0.31 ± 0.01 µmol min⁻¹ mg⁻¹) with 41% of enantiomeric excess towards S(+)‐ibuprofen in 24 h reaction. Under similar reaction conditions, the commercial counterpart Novozym® 435 showed 34% conversion (0.091 ± 0.003 µmol min⁻¹ mg⁻¹) and 16% of enantiomeric excess. <b>Conclusion</b>: The molecular association between the protein and the polyols exerts a positive cooperativism which prevents aggregation of the protein and protects its active conformation. The residual esterase activity of the immobilized CALB compared with the free lipase depends directly on the amount of co‐adsorbed polyols. Moreover, polyols boost the catalytic performance in the kinetic resolution of racemic ibuprofen showing an optimum at the maximum coverage of polyols on the biocatalysts.