Production of low-calorie structured lipids from spent coffee grounds or olive pomace crude oils catalysed by immobilized lipases in magnetic nanoparticles

Low-calorie lipids of the type MLM are triacylglycerols (TAG) containing a long-chain fatty acid (L) at the position sn-2 and medium-chain fatty acids (M), at the positions sn- 1 ,3. This type of structured lipids, with a caloric value of 5-7 kcal/g against 9 kcal/g ofnatural fats, can be synthesized either (i) by acidolysis of a TAG or an oil containing long-chain fatty acids, with a medium-chain fatty acid, or (ii) by interesterification of a TAG or oil with a medium-chain fatty acid ester (usually ethyl or methyl esters). The aim of this study was to produce MLM by acidolysis of crude oils extracted from agro-residues namely spent coffee grounds and olive pomace, with capric acid (Cl 0:0) or by-interesterification of these oils with ethyl caprate (C I OEE), in solvent-free media, catalysed by sn-1,3 regioselective lipases. The commercial immobilized lipase from Thermomyceslanuginosus (Lipozyme TLIM, Novozymes A/S, Denmark) and the Rhizopus oryzaelipase immobilized in magnetic nanoparticles (MNP-lipase) were tested. When Lipozyme TLIM was ll$d, 39 or 51 % of new TAG were obtained after 48 h reaction of crude olive pomace oil with C 10:0 or Cl OEE, while 48 and 66% were obtained from spent coffee grounds oil, after 48 h and 24 h reaction, respectively. Thðreactions were faster with MNP-lipase than with Lipozyme TL 1M and the equilibrium was attained after and 5 h with a new TAG yield of 51 and 56%, obtained by acidolysis of crude olive pomace or spent coffee grounds oilswith C 10, respectively. New TAG yields of46 and 26% were observed after 3 and 5 h interesterification of crude olive pomace or spent coffee grounds oils with C 1 OEE, respectively. The operational stability ofMNPlipase was assayed in five 24 Il-consecutive batches in presence of crude olive pomace oil and evaluated in terms of TAG conversion: a Sadana deactivation kinetics was observed with half-lives of 163 h in acidolysis, and 220 h in the interesterification with Cl OEE. The use of low-cost feedstocks and a biocatalyst with high activity and stability will reduce process costs. These are promising results towards the sustainability of MLM production.