Studies of the fatty acid specificity of the lipase fromRhizomucor miehei toward 20:1n‐9, 20:5n‐3, 22:1n‐9 and 22:6n‐3

The fatty acid specificity of the lipase fromRhizomucor miehei toward 20:1n‐9, 20:5n‐3, 22:1n‐9 and 22:6n‐3 has been determined by comparing the alcoholysis (byn‐propanol) of various mixtures of C20 and C22 fatty acids (FFA) or the corresponding ethyl esters (FAEE) inn‐heptane. For all the fatty acids examined, the degree of conversion was much higher when using FFA rather than FAEE. When comparing the experiments with either single FAEE or FAEE mixtures, it was found for all four fatty acids that the degree of conversion depended on whether the FAEE was alone or together with other fatty acids in the reaction mixture. The lipase showed a strong specificity toward 20:1n‐9, whereas the polyunsaturated fatty acids were much poorer substrates, especially 22:6n‐3. The degrees of conversion for the two n‐3 fatty acids show a clear preference for 20:5n‐3 over 22:6n‐3, not only when present alone but also in the different mixtures examined. The results obtained in the present experiments therefore suggest that when using the lipase fromR. miehei for enrichment of fish oils with n‐3 fatty acids, it should not only be possible to diminish the content of 20:1 and 22:1 present in the outer positions in the triacylglycerols, but also to incorporate relatively more 20:5n‐3 than 22:6n‐3 into the triglycerides.