Optimization of Candida antarctica lipase immobilization in xerogels using an ionic liquid additive: enhanced esterification activity and thermal stability

Abstract

The immobilization of Candida antarctica lipase B (CALB) within xerogels synthesized through the sol-gel method was investigated, employing the ionic liquid 1-octyl-3-methylimidazolium bromide (C₈MI.Br) as an additive to enhance enzymatic performance. The optimization of enzyme mass and ionic liquid concentration, using a central composite experimental design, identified optimal conditions of 0.27 g/mL enzyme and 1.53% ionic liquid, yielding a maximum total esterification activity exceeding 500 U. Structural characterization, including BET surface area analysis and X-ray diffraction, confirmed the formation of a porous, amorphous matrix conducive to enzyme stability and activity. The incorporation of the ionic liquid significantly enhanced the xerogels’ thermal and operational stability. Residual esterification activity was maintained at approximately 80% after 100 days under refrigeration, and the xerogels exhibited reusability for up to eight catalytic cycles with residual activity above 50%. Furthermore, thermal stability assessments demonstrated superior resistance of the immobilized enzyme to elevated temperatures compared to its free counterpart. This study underscores the critical role of ionic liquids as additives, facilitating the formation of structurally optimized xerogels while preserving enzyme activity and stability. The findings suggest significant potential for industrial biocatalytic processes, offering a sustainable and efficient approach to enzyme immobilization for applications requiring enhanced catalytic performance and longevity.

Graphical Abstract