Esterification reactions catalyzed by lipase encapsulated in sodium Bis(2-ethylhexyl)phosphate(NaDEHP) reverse micelles

Abstract

Lipases have increasingly been used transformation of water insoluble substrates such as hydrolysis of triglycerides to glycerol and fatt acids, and esterification reactions. This catalytic process is heterogeneous and can be favored by the use of water-in-oil microemulsions or reverse micelles due to their low water content. In this study, the catalytic activity of Rhizomucor delemar lipase encapsulated in reverse micelles formed by sodium bis (2-ethylhexyl) phosphate (NaDEHP) in isooctane was investigated using various alcohols with fatty acids. The effects of nature of substrates and various system parameters such as salt concentration and water to surfactant ratio (W) on activity of encapsulated lipase were examined in relation to the reverse micellar structure and selectivity. R. delemar lipase showed selectivity with regard to a structure of substrates used. Long chain fatty acids and alcohols were better catalyzed as compared to the short chain ones. The observed results may be related to the enzyme localization in ther reverse micellar microstructure resulting from the liophilic character of protein and the availability of substrates. The results also showed that W has a strong impact on the enzyme activity. Maximum reaction rate was observed at W 6 and the rates obtained were found to be 50-100 times those obtained in general oil/water media.