The comparative discriminating abilities of lipases in different media andtheir application in fatty acid enrichment

The generally held belief that the selectivity of lipase can be changed by changing the media from aqueous to non-aqueous was tested by monitoring the rates of hydrolysis, ester synthesis and transesterification with a range of fatty acid mono-esters. Although the absolute rates of reaction varied, hydrolysis was by far the most rapid of the three, the relative rates for t he fatty acids used were similar in all three reaction types. The selectivi ty of the five enzymes used appeared to remain unchanged irrespective of th e type of reaction, i.e. hydrolysis of p-nitrophenyl eaters, direct ester s ynthesis with butanol and fatty acid or transesterification with butyl buty rate and fatty acid, and could not be changed by changing water activity. T his principle was applied to screen for suitable lipases which could be use d to increase the gamma linolenic acid content of a fatty acid mixture. Enz ymes could be selected by measuring the rate of hydrolysis of a range of p- nitrophenyl esters.