Reversed Micelle Lipase-catalyzed Synthesis Of Isoamyl Butyrate Amyl

Lipase-catalyzed esterifications reaction of organic synthesis has become a fashioned tool of stereo-specific organic chemistry , which has been reported in many literatures . However, most of the work on lipase-catalyzed esterifications reported in the literatures have been based on reactions using longer-chain length substrates, the esterifications of short-chain fatty acids and alcohols have received little attention .Low molecular weight esters are responsible for the aroma of many fruits and constitute mainly short-chain fatty acid derivatives like acetate, propionate, butyrate and isobutyrate. For example, ethyl, butyrate and isoamyl isobutyrate are presented in the aroma of strawberry and banana, respectively. Isoamyl esters are valuable and high-demand flavour compounds of commercial importance, and are widely used in the food, beverage, cosmetic and pharmaceutical industries etc. Natural flavour esters extracted from plant sources are often in short supply or expensive. Moreover, flavour quality and quantity varies from region to region, Most of these esters can also be produced chemically by acid -catalyzed condensation of an alcohol and an acid at elevated temperatures . However, recent trends in consumer preference toward 'natural' products indicate that biocatalysis may have an advantage over chemical synthesis as products of biocatalysis may have a 'natural' label. It was also observed that fatty acid esters, synthesized by enzymes such as lipase, often have better odour and flavour characteristics compared to similar esters produced by conventional means.Presently, immobilized Rhizomucor miehei lipozyme IM-20 has been used to catalyze the esterification reaction between isobutyric acid and isoamyl alcohol to synthesize isoamyl isobutyrate in n-hexane, which has been proved to be an effective method. But it is not fit for industrialproduction because of the high price of the lipase . However, this esterification catalyzed by lipase in reversed micelles has not been reported . We use another easily obtained lipase (which has much lower activity than Rhizomucor meihie lipozyme IM-20 lipase has in n-hexane) with much lower price compared with the Rhizomucor miehei, and by investigating systematically the regularities of the effects of water content, pH of buffer, temperature and the ratio of substrate/enzyme optimize the suitable condition for the esterification reaction between isobutyric acid and isoamyl isobutyrate in two kinds of typical reversed micelles of AOT and CTAB. Experimental results show that the two kinds of reversed micelles both provide suitable environment for the lipase (CCL), which show superactivity-four and six times as that in n-hexane respectively. The activity of lipase(CCL) in AOT reversed micelles is close to that of Rhizonucor meihei lipozyme IM-20 in n-hexane, while the activity in CTAB reversed micelle is higher than that of Rhizonucor meihei in n-hexane reported in literature, which has certified sufficiently that the microstructure of reversed micelle has obvious superiority which can simulate the natural biological environment for lipase to perform its function, and can lay a foundation for the future work on esterification synthesis between short-chain fatty acids and alcohols.