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Abstract
This work aims to produce triacylglycerols (TAG) containing a medium-chain fatty acid (M) at positions sn-1,3 and a long-chain fatty acid (L) at sn-2 position, i.e. TAG of MLM type, by acidolysis of virgin olive oil with caprylic (C8:0) or capric (C10:0) acids, catalyzed by 1,3-selective Rhizopus oryzae heterologous lipase (rROL) immobilized in Eupergit® C and modified sepiolite. This lipase was produced by the methylotrophic yeast Pichia pastoris. Reactions were performed at 25 and 40 °C, for 24 h, either in solvent-free or in n-hexane media, at a molar ratio 1:2 (olive oil:free fatty acid). Higher incorporations of C8:0 (21.6 mol%) and C10:0 (34.8 mol%) into the TAG were attained in solvent-free media, at 40 °C, when rROL immobilized in Eupergit® C was used. In organic media, at 40 °C, only 15.9 and 14.1 mol%, incorporation of C8:0 or C10:0 were, respectively observed. Lower incorporations were attained for both acids (3.4-7.0 mol%) when native ROL (nROL) in both supports and rROL in modified sepiolite were used. rROL in Eupergit® C maintained its activity during the first four or three 23-h batches, respectively when C8:0 (half-life time, t^sub 1/2^ = 159 h) or C10:0 (t^sub 1/2^ = 136 h) were used, decreasing thereafter following a time delay model.
Keywords Acidolysis * Capric acid * Caprylic acid * Olive oil * Rhizopus oryzae lipase * Structured lipids
Abbreviations
FFA Free fatty acid(s)
L Long-chain fatty acid(s)
M Medium-chain fatty acid(s)
MAG Monoacylglycerol(s)
MLM Triacylglycerol(s) containing medium-chain fatty acid at sn-1 and sn-3 positions (M) and a long-chain fatty acid (L) at position sn-2
nROL Native ROL
rROL Heterologous ROL
ROL Rhizopus oryzae lipase
SL Structured lipid(s)
TAG Triacylglycerol(s)
t^sub 1/2^ Half-life time
(ProQuest: ... denotes formulae omitted.)
Introduction
The production of triacylglycerols (TAG) with medium chain fatty acids, M, in positions sn-l and sn-3, and a long-chain fatty acid, L, in the internal position, i.e. of MLM type, has recently increased due to its nutritional interest. These are low calorie and dietetic structured lipids (SL) adequate to control obesity and also for persons with fat malabsorption and other metabolism problems [1,2]. The presence of medium-chain fatty acids and longchain fatty acids in the same TAG molecule will contribute to the unique nutritional and metabolic...