Catalyzed esterification reaction by lipase encapsulated in sodium bis(2-ethylhexyl) phosphate(NaDEHP) reverse micelles

Abstract

The use of reverse micelle as a reaction medium for reactions catalyzed by enzymes has received increasing attention in recent years since it can enhance the activity of the enzyme and its interaction with substrate. In this study, esterification reactions of two fatty acids (caprylic and oleic acid) and hexanol catalyzed by Thai rice bran lipase (TRBL) encapsulated in reverse micelles formed by bis(2-ethyhexyl) phosphate (NaDEHP) in isooctane were investigated. It was found that the enzymatic activity of TRBL depended strongly on the reverse micellar structure, water content (W0), type and concentration of the substrate. In this reverse micellar system, Thai rice bran lipase was showed to have a preference towards long chain fatty acid which is expected to be due to the localization of enzyme molecules in the reverse micelle microstructure and the availability of substrates. Furthemore, the optimum W0 for TRBL in this system was found to be approximately 8. Under specific conditions, the conversion of nearly 90% could be obtained from the esterification reaction catalyzed by a freshly extracted TRBL. The reaction rate and conversion appeared to be influenced by a combined effect of several factors such as salt concentration, type and concentration of substrate and water content.