Response surface modeling of glycerolysis catalyzed by Candida rugosa lipase immobilized in different polyurethane foams for the production of partial glycerides

Monoglycerides (MG) and diglycerides (13G) are the most widely used emulsifiers in food and pharmaceutical industries. In this study, MG and DG were produced by inter-esterification of refined olive residue oil with glycerol (glycerolysis), in n-hexane, catalyzed by Candida rugosa lipase immobilized in different biocompatible hydrophilic polyurethane foams, A and B. These foams, with aquaphilicities of 3.7 and 2.8, were prepared with a toluene diisocyanate ("Hypol FHP 2002(TM)'') and a diphenylmethane diisocyanate ("Hypol FHP X4300(TM)'') pre-polymer, respectively. Response surface methodology was used for modeling the reaction, as a function of the molar ratio glycerol/triglycerides (Gly/TG, 0.5-2.0) and the initial water activity (a(w)) of the biocatalyst (A, 0.24-0.91; B, 0.37-0.91). Experiments were carried out following a central composite rotatable design. With lipase in foam A, production of MG and DG could be described by first order polynomials. With foam B, MG and DG production could be fitted to concave and flat surfaces, described by a second and a first orders polynomials, respectively. The best productions of MG and DG were achieved with the lipase in the less hydrophilic foam, B: at 24 h reaction time, 32% (w/w) MG and 18% (w/w) DG were obtained, when the initial aw of the biocatalyst was 0.83, with a Gly/TG of 1. (C) 2002 Published by Elsevier Science B.V.