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 l ipases, lipase A and lipase B, lipase B being highly specific for hydr olysis of esters of cis-DELTA9 fatty acids. We now describe the behavi or 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 hyd rolysis measured in the organic solvent system were much lower than th ose observed with aqueous emulsions of the substrates, but the system allowed use of high-melting-point substrates in a liquid state. The im mobilized lipases in organic media were found to have the same specifi cities as the free lipases acting on aqueous emulsions of the substrat es. Lipase B was highly specific for (esters of) unsaturated fatty aci ds with a cis-double bond in the 9-position, but also catalyzed to som e 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.