Batch and Continuous Lipase-Catalyzed Production of Dietetic Structured Lipids from Milk Thistle, Grapeseed, and Apricot Kernel Oils

The sustainable production of healthy structured lipids (SLs) using oils extracted from agro-industry by-products or non-conventional lipid sources is of utmost importance in the framework of a circular bioeconomy, toward a zero-waste goal. In this study, low-calorie triacylglycerols (TAGs) containing a long-chain (L) fatty acid (FA) at position sn-2 and medium-chain (M) FAs at positions sn-1,3 (MLM type SL) were obtained from virgin cold-pressed milk thistle (51.55% linoleic acid; C18:2), grapeseed (66.62% C18:2), and apricot kernel (68.61% oleic acid; C18:1) oils. Lipase-catalyzed acidolysis with capric acid (C10:0) or interesterification with ethyl caprate (C10 Ethyl) in solvent-free media were performed. In batch reactions, immobilized Rhizomucor miehei lipase (Lipozyme RM) was used as a biocatalyst. For all tested oils, new TAG (SL) yields, varying from 61 to 63%, were obtained after 6 h of interesterification. Maximum new TAG yields were reached after 6, 24, and 30 h of acidolysis with grapeseed (64.7%), milk thistle (56.1%), or apricot kernel (69.7%) oils, respectively. Continuous acidolysis and interesterification of grapeseed oil were implemented in a packed-bed bioreactor, catalyzed by immobilized Thermomyces lanuginosus lipase (Lipozyme TL IM). Throughout 150 h of continuous operation, no lipase deactivation was observed, with average SL yields of 79.2% ± 4.1 by interesterification and 61.5% ± 5.91 by acidolysis.