Abstract
In this study, Candida rugosa lipase (CRL) was immobilized into modified hollow mesoporous silica (HMSS) materials with different hydrophobicity. Among propyl-(C3), phenyl-(C6), octyl-(C8), and octadecyl-(C18) modified HMSS as well as native HMSS, taking advantage of more hydrophobic microenvironment, the HMSS-C18-CRL showed exceptional performance in enzymatic esterification reaction. Using the novel HMSS-C18 with immobilized CRL (HMSS-C18-CRL), we investigated the esterification of phytosterols with polyunsaturated fat acid (PUFA) in a solvent-free system for the production of phytosterols esters. Response surface methodology (RSM) was applied to model and optimize the reaction conditions, namely, the enzyme load (5–25%), reaction time (10–110 min), molar ratio of α-linolenic acid (ALA)/phytosterols (1:1–7:1) and represented by the letters E, T, and M respectively. Best-fitting models were successfully established by multiple regressions with backward elimination. The optimum production was achieved at 70 min for reaction time, 20% based on the weight of substrate for enzyme loading, and 5.6:1 for ALA/phytosterols molar ratio. Under optimized conditions, a conversion of about 90 ± 2% was achieved. These results indicated that HMSS-C18-CRL demonstrates to be a promising catalyst and can be potentially applied in the functional lipid production.
Highlights
Enzymes are versatile as biocatalysts for the green synthesis of chemicals and pharmaceuticals due to the milder catalytic conditions, higher catalytic efficiency, and fewer side effects as compared to chemical catalysts [1,2,3]
Free lipase has not been widely applied on an industrial scale for the challenges associated with its poor durability and recyclability
response surface methodology (RSM) was successfully applied to model and optimize the conditions used in the esterification reaction and the optimized process variables were reproducible
Summary
Enzymes are versatile as biocatalysts for the green synthesis of chemicals and pharmaceuticals due to the milder catalytic conditions, higher catalytic efficiency, and fewer side effects as compared to chemical catalysts [1,2,3]. The immobilization of lipase could overcome those difficulties, and endow the biocatalysts with special properties, such as higher activity, modulation of the enzyme selectivity and decrease of the reaction inhibition [4]. There are four main methods for immobilization of enzyme pertaining to physical adsorption, covalent binding, cross-linked enzyme aggregates and entrapment. Among those methods, the immobilization of adsorption is the most important and useful method and many studies about immobilization based on adsorption were conducted with different novel supports [2]
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