Optimization of Lipase-Catalyzed Fractionation of Two Conjugated Linoleic Acid (CLA) Isomers
The separation of two isomers of conjugated linoleic acid is highly significant since each exhibits different biochemical properties. The aim of this study was to investigate and optimize several factors affecting the esterification of L-menthol with the c9,t11-CLA isomer in an organic solvent-free system using lipase from Candida rugosa (Lipase AY-30). D-optimal design with 5 factors and 3 levels were employed to evaluate the effects of synthesis parameters; reaction time (8–24 h), temperature (30–50 _C), enzyme content (2–20 U/ml), substrate molar ratio of conjugated linoleic acid oil to L-menthol (2:1–1:2) and pH (6–8) on esterification of c9,t11-CLA with L-menthol. Based on the analysis of the residual amount of c9,t11-CLA in the free fatty acid fraction after just one-step esterification, the optimum synthesis conditions were as follows: reaction time 23.12 h, temperature 32.65 _C, enzyme amount 135.40 U, molar ratio of CLA oil to L-menthol at 1:1.7 and pH at 7.7; the lowest purity of c9,t11-CLA in free fatty acid fraction based on the total content of c9,t11 and t10,c12-CLA isomers was 8.6 %.