STEREOSELECTIVITY OF LIPASES IN SUPERCRITICAL CARBON-DIOXIDE .1. DEPENDENCE OF THE REGIOSELECTIVITY AND ENANTIOSELECTIVITY OF PORCINE PANCREAS LIPASE ON THE WATER-CONTENT DURING THE HYDROLYSIS OF TRIOLEIN AND ITS PARTIAL GLYCERIDES

The stereoselectivity of porcine pancreas lipase (PPL) was investigate d during the enzymatic hydrolysis of triolein and its partial glycerid es in the presence of supercritical carbon dioxide (SCCO2) as reaction medium. The water content of the immobilized lipases was varied. The partial glycerides were separated into mono- and diglycerides by TLC, converted to their 3,5-dinitrophenylurethane derivatives and subsequen tly resolved into sn-1,2 and sn-2,3 enantiomers (estimation of diolein s) or into sn-1 and sn-3 enantiomers (estimation of monooleins) by HPL C on a chiral stationary phase (Sumichiral OA-4100). In all reactions under the conditions employed, PPL revealed a distinct preference for the sn-3 position of the glycerol. However, the stereoselectivity depe nds on the reaction time, the substances initially used and the enzyme water content. It seems that the effect of the enzyme water content o n the activity and selectivity of porcine pancreas lipase in SCCO2 is based on a modification of the 'micro-environment' of the enzyme by th e solution of CO2 in water, causing a decrease of the pH value.