Selective Enrichment of Conjugated Linoleic Acid Isomers in Their Mixtures Using Combined Chemical and Enzymatic Methods

Abstract

AbstractThe aim of this study was to selectively enrich t10,c12‐conjugated linoleic acid (t10,c12‐CLA) and c9,t11‐CLA in commercial CLA mixtures using a combination of urea crystallization and lipase‐catalyzed esterification. The objective of the urea fractionation is to remove saturated and monounsaturated fatty acids (FA) from the CLA mixtures. CLA‐enriched free FA (FFA) mixtures containing 53.8 wt% t10,c12‐CLA and 39.1 wt% c9,t11‐CLA were produced from the CLA mixtures containing ~34 wt% each of the two CLA isomers by a urea crystallization using methanol and the urea‐to‐FA weight ratio of 2.5:1. The CLA‐enriched FFA mixtures were partially esterified with dodecan‐1‐ol in a recirculating packed‐bed reactor using an immobilized lipase from Candida rugosa to further enrich the t10,c12‐CLA and c9,t11‐CLA in an FFA fraction and an FA dodecyl ester fraction, respectively, under the optimal conditions, i.e., temperature, 20 °C; FA‐to‐dodecan‐1‐ol molar ratio, 1:1; water content, 2 wt% of total substrates; residence time, 5 min; and reaction time, 24 h (for t10,c12‐CLA enrichment) and 12 h (for c9,t11‐CLA enrichment). After the reaction, an FFA fraction with 72.6 wt% t10,c12‐CLA was obtained. Another FFA fraction with 62.0 wt% c9,t11‐CLA was recovered after the saponification of the FA dodecyl ester fraction. The yields of t10,c12‐CLA and c9,t11‐CLA in the FFA fractions were 43.6 and 21.5 wt%, respectively, based on their initial weights in the CLA mixtures.