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

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 (R) MP 1000, Eupergit (R) C and Lewatit (R) VP OC 1600) and tested as catalysts for the acidolysis between tripalmitin and oleic acid, batchwise, at 60 degrees C. in solvent-free medium. The highest molar incorporations of oleic acid in the triacylglycerols were achieved with rROL in Lewatit (R) VP OC 1600 and Accurel (R) MP 1000, although the highest immobilization yields were observed with Eupergit (R) C. Quasi-equilibrium was attained after 6h or 12h reaction, with about 30 mol.% and 22 mol.% 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 (t(1/2)) of 34.5 h and 64.0 h were achieved for rROL immobilized in Accurel (R) MP 1000 and in Lewatit (R) 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 (t(1/2) = 202 h). Thus, the loss of activity may be explained by a progressive dehydration occurring along the reaction. (C) 2012 Elsevier B.V. All rights reserved.