Preparation of functional oils rich in diverse medium and long-chain triacylglycerols based on a broadly applicable solvent-free enzymatic strategy

Abstract

To address the problems of long reaction times and limited range of adaptation in enzymatic synthesis medium- and long-chain triacylglycerols (MLCTs), a broadly applicable solvent-free enzymatic interesterification strategy was proposed. Candida sp. lipase (CSL) was immobilized on hydrophobic hollow mesoporous silica spheres (HHSS) to construct a biocatalyst designated as CSL@HHSS with a 15.3 % immobilization yield and a loading amount of 94.0 mg/g. The expressed activity and the specific activity were 20.14 U/g and 173.62 U/g, which were 4.6 and 5.6 times higher than that of free CSL, respectively. This biocatalyst demonstrated higher activity, wider applicability, and excellent reusability. Linseed oil, sunflower oil, perilla seed oil, algal oil, and malania oleifera oil were applied as substrates to produce MLCTs with medium-chain triacylglycerols (MCT) catalyzed by CSL@HHSS through interesterification in yields ranging from 69.6 % to 78.0 % within 20 min. Specific fatty acids, including linolenic acid, oleic acid, DHA, and nervonic acid (the first reported), were introduced into MLCT's skeleton, respectively. The structures were finely analyzed and identified by GC and UPLC-MS. The catalytic efficiency value of CSL@HHSS in catalyzing interesterification between linseed oil and MCT (70 ℃, 20 min, lipase 6 wt%) is 0.86 g/g∙min, which is the highest ever reported. This paper presents an effective and sustainable strategy for functional MLCTs production.

Keywords: Candida sp. lipase (CSL); Enzymatic interesterification; Essential fatty acids; Hydrophobic porous materials; Immobilization enzyme; Nervonic acid; Structured triacylglycerol.