HYDROLYSIS OF EDIBLE OILS BY LIPASES IMMOBILIZED ON HYDROPHOBIC SUPPORTS - EFFECTS OF INTERNAL SUPPORT STRUCTURE

The hydrolysis of edible oil by immobilized lipases on novel support materials was investigated. Six hydrophobic polymers were studied with the following techniques: (i) determination of the surface area of each support by BET (Brunauer-Emmett-Teller) analysis of nitrogen adsorption isotherms; (ii) electron photomicrography; and (iii) measuring lipase activity by hydrolysis of olive oil with lipase from Candida cylindracea immobilized on each support. A detailed structural analysis on one support also was carried out by mercury porosimetry. The composition and porosity of a support are more important than the surface area in determining activity for immobilized lipases. Furthermore, having selected the ''most efficient'' support, five lipases from C. cylindracea, Rhizomucor miehei, and Pseudomonas cepacia, were immobilized, and their hydrolytic activities were determined at several temperatures and pH values with olive oil and beef tallow as substrates in solvent-free systems. For each parameter, twelve successive 2.5-h hydrolysis reactions were conducted on a laboratory-scale under batch conditions. Lipase AY from C. cylindracea had the highest hydrolytic activity, in the range of 30-50 degrees C at pH 5.5 with olive oil as the substrate. For beef tallow, lipase PS, from P. cepacia, displayed the highest activity at 50 degrees C and pH 7.