Camelina oil as a source of polyunsaturated fatty acids for the production of human milk fat substitutes catalyzed by a heterologous Rhizopus oryzae lipase

This study aims to produce human milk fat substitutes (HMFS) rich in polyunsaturated fatty acids (PUFA), mainly the essential omega-3 linolenic acid, by acidolysis reaction between tripalmitin (PPP) and free fatty acids (FFA) from camelina oil, in stirred batch reactor and solvent-free media. The non-commercial heterologous Rhizopus oryzae lipase (rROL), immobilized on Lewatit VP OC 1600 or on Relizyme OD403/S, and the immobilized commercial lipase from Rhizomucor miehei (Lipozyme RM IM) were tested as biocatalysts. Both lipases are sn-1,3 selective. After 24 h reaction at 60°C, using biocatalyst loads of 5 wt% (in relation to tripalmitin), 48.9, 43.6, and 18.3 mol% of fatty acid incorporation in triacylglycerols (TAG) were obtained with Lipozyme RM IM and rROL immobilized on Lewatit or on Relizyme, respectively. rROL immobilized on Lewatit was selected as biocatalyst for the acidolysis, as alternative to the commercial immobilized lipases. With this biocatalyst, the molar incorporation increased with its initial water activity (0.55–0.95). Modeling acidolysis catalyzed by rROL immobilized on Lewatit was performed by response surface methodology, as a function of temperature (58–72°C) and molar ratio FFA:PPP (1.2:1–6.8:1). The highest PPP consumption was achieved at 60°C with a molar ratio of 2:1. The yield of HMFS (new TAG) increased from 42.6 wt% (5% biocatalyst load) to 52% with 8% load, after 24 h acidolysis. Practical applications: Camelina oil showed to be a good source of PUFA, mainly essential fatty acids, to incorporate in HMFS. After 24 h acidolysis under optimized conditions, catalyzed by the non-commercial sn-1,3 regioselective rROL immobilized on Lewatit VP OC 1600, the TAG fraction contains 67.7 mol% of palmitic acid at position 2. These structured lipids rich in PUFA can be used in blends with 1,3-dioleoyl-2-palmitoyl-glycerol (OPO) in order to mimic the human milk fat. The performance of this biocatalyst was comparable to that observed with Lipozyme RM IM. The replacement of high-cost commercial immobilized lipases by rROL immobilized on Lewatit may reduce the biocatalyst cost. In addition, since the best molar ratio FFA:PPP for rROL is 2:1, i.e., the stoichiometric value for the acidolysis catalyzed by sn-1,3 regioselective lipases, the use of this biocatalyst will reduce downstream costs related with unconverted FFA recovery. The performance of rROL immobilized on Lewatit VPOC 1600 is comparable to that of Lipozyme RM IM. After 24 h acidolysis, under optimized conditions, triacylglycerols contain 67.8 mol% palmitic acid at position-2.