Esterification by Rhizopus delemar lipase in organic solvent using sugar ester reverse micelles

The esterification of oleic acid with octyl alcohol catalyzed by Rhizopus d elemar lipase was investigated in reverse micellar system of sugar ester DK -F-110. High initial reaction rate was obtained by preparing the micellar o rganic phase with extremely low water content. The maximum rate was obtaine d at a W-0 (= [H2O]/[amphiphile]) of 2.5. The highest reaction rate occurre d at pH 6. With decreasing DK-F-110 concentration, the initial reaction rat e was slightly decreased. The optimal temperature for lipase activity was a round 313 K (40 degreesC). Apparent activation energy of the esterification in the system was 43.7 kJ/mol. The lipase showed 40% of its esterification activity after 28 h incubation in the DK-F-110 micellar organic phase. The reaction kinetics in this system were recognized as ping-pong bi-bi mechan ism. From a Michaelis-Menten analysis, apparent kinetic parameters were det ermined. The turnover number of the DK-F-110 system was larger than that of the sodium bis(2-ethylhexyl)sulfosuccinate (AOT) system. (C) 2001 Elsevier Science B.V. All rights reserved.