Fractionation and enrichment of CLA isomers by selective esterification with <i>Candida rugosa</i> lipase

Abstract

Abstract A commercial product of CLA contains almost equal amounts of cis ‐9, trans ‐11 ( c 9, t 11)‐CLA and trans ‐10, cis ‐12 ( t 10, c 12)‐CLA. We attempted to enrich the two isomers by a two‐step selective esterification using Candida rugosa lipase that acted on c 9, t 11‐CLA more strongly than on t 10, c 12‐CLA. An FFA mixture containing CLA isomers was esterified with an equimolar amount of lauryl alcohol in a mixture of 20% water and the lipase. When the esterification of total FA reached 50%, two isomers were fractionated in a good yield: t 10, c 12‐CLA was enriched in FFA, and c 9, t 11‐CLA was recovered in lauryl esters. The FFA were esterified again to enrich t 10, c 12‐CLA. At 27.3% esterification of total FA, the t 10, c 12‐CLA content in FFA increased to 64.8 wt% with 89.3% recovery: The ratio of the content of t 10, c 12‐CLA to that of two isomers was 95.9%. Lauryl esters obtained by the single esterification were employed for enrichment of c 9, t 11‐CLA. After the esters were hydrolyzed, the resulting FFA were esterified again with lauryl alcohol. At 62.0% esterification of total FA, the c 9, t 11‐CLA content in lauryl esters increased to 73.3 wt% with 79.4% recovery: The ratio of the content of c 9, t 11‐CLA to that of two isomers was 95.6%. In a 600‐g‐scale purification, molecular distillation was effective in separating the reaction mixture into lauryl alcohol, FFA, and lauryl ester fractions.