The Catalytic Properties of HTAB-Alkanol-Hydrocarbon-Water Microemulsion System for Esterification

Microemulsions have been widely reviewed, not only as effective media for enzyme reactions requiring hydrophobic solvents but have also attracted wide interest as possible low-toxicity, low-cost media for tertiary oil recovery, formation of nanoparticles and decomposition of toxic pollutants. These fluids can be tuned for specific applications by adjusting their compositions. A water-in-oil (w/o) microemulsion system was developed in this study based on cationic surfactant, tert-amyl alcohol, aliphatic hydrocarbon and aqueous buffer. The microemulsion – HTAB/2M2B-Hexane/buffer – was then used as a reaction medium for lipase-catalysed esterification of sucrose and lauric acid. The synthetic activities of Lipozyme and Novozyme in the microemulsion were compared with activities in four other reaction media: hexane, isoocatane, tert-amyl alcohol (2M2B) and HTAB/2M2B/buffer. The microemulsion was found to be the best medium for the synthesis of sucrose lauryl esters, with Lipozyme showing higher activity compared to Novozyme. Lipozyme activity was found to increase as the incubation time increased; reverse effect was observed with Novozyme. Microemulsion system with 5/95 surfactant ratio and 5% water gave the highest yield of sugar ester by Lipozyme. This microemulsion can be proposed as a highly potential reaction medium for high productions of the industrially-important sugar ester.