Fractionation and enrichment of CLA isomers by selective esterification with Candida rugosa lipase

A commercial product of CLA contains almost equal amounts of cis‐9,trans‐11 (c9,t11)‐CLA and trans‐10,cis‐12 (t10,c12)‐CLA. We attempted to enrich the two isomers by a two‐step selective esterification using Candida rugosa lipase that acted on c9,t11‐CLA more strongly than on t10,c12‐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: t10,c12‐CLA was enriched in FFA, and c9,t11‐CLA was recovered in lauryl esters. The FFA were esterified again to enrich t10,c12‐CLA. At 27.3% esterification of total FA, the t10,c12‐CLA content in FFA increased to 64.8 wt% with 89.3% recovery: The ratio of the content of t10,c12‐CLA to that of two isomers was 95.9%. Lauryl esters obtained by the single esterification were employed for enrichment of c9,t11‐CLA. After the esters were hydrolyzed, the resulting FFA were esterified again with lauryl alcohol. At 62.0% esterification of total FA, the c9,t11‐CLA content in lauryl esters increased to 73.3 wt% with 79.4% recovery: The ratio of the content of c9,t11‐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.