SPECIFICITIES OF IMMOBILIZED GEOTRICHUM-CANDIDUM CMICC-335426 LIPASE-A AND LIPASE-B IN HYDROLYSIS AND ESTER SYNTHESIS REACTIONS IN ORGANIC-SOLVENTS

Geotrichum candidum CMICC 335426 was previously shown to produce two lipases, lipase A and lipase B, lipase B being highly specific for hydrolysis of esters of cis-DELTA9 fatty acids. We now describe the behavior of immobilized lipases A and B in organic solvents. Ester synthesis reactions were run in petroleum ether, and hydrolysis reactions were carried out in tri-n-butylphosphate containing water. The rates of hydrolysis measured in the organic solvent system were much lower than those observed with aqueous emulsions of the substrates, but the system allowed use of high-melting-point substrates in a liquid state. The immobilized lipases in organic media were found to have the same specificities as the free lipases acting on aqueous emulsions of the substrates. Lipase B was highly specific for (esters of) unsaturated fatty acids with a cis-double bond in the 9-position, but also catalyzed to some extent reactions involving (esters of) the saturated 8:0 fatty acid; lipase A was much less specific and used a wider range of substrates including (esters of) saturated fatty acids and oleic acid isomers. We obtained specificity constants (k(cat)/K(m)) for the lipase-catalyzed esterification of a few fatty acids, and confirmed the specificities of the lipases.