Immobilized heterologous Rhizopus oryzae lipase: A feasible biocatalyst for the production of human milk fat substitutes

Abstract

This work aims at evaluating the potentialities of a heterologous Rhizopus oryzae lipase (rROL) as a feasible biocatalyst, to be used as an alternative to commercial lipases, for the synthesis of Human Milk Fat Substitutes (HMFS). This enzyme was immobilized in three different supports (Accurel® MP 1000, Eupergit® C and Lewatit® VP OC 1600) and tested as catalysts for the acidolysis between tripalmitin and oleic acid, batchwise, at 60°C, in solvent-free medium.The highest molar incorporations of oleic acid in the triacylglycerols were achieved with rROL in Lewatit® VP OC 1600 and Accurel® MP 1000, although the highest immobilization yields were observed with Eupergit® C.Quasi-equilibrium was attained after 6h or 12h reaction, with about 30mol.% and 22mol.% of oleic acid incorporation, when rROL immobilized in Lewatit and Accurel were used, respectively.Also, 23h batch operational stability tests were performed: half-life times (t1/2) of 34.5h and 64.0h were achieved for rROL immobilized in Accurel® MP 1000 and in Lewatit® VP OC 1600, respectively. An important increase in the operational stability was observed for rROL immobilized in Lewatit after rehydration at the end of each batch (t1/2=202h). Thus, the loss of activity may be explained by a progressive dehydration occurring along the reaction.