Lipase-catalyzed glyceride synthesis in a foam reactor.

Abstract

We have investigated the lipase-catalyzed glyceride synthesis in a foam reactor. From the experimental results, we conclude that the reaction yields have been significantly enhanced due to enhanced foaming. More importantly, the dominant products are valuable commercial emulsifiers, monoglycerides and diglycerides. In foam media, given that the foaming is carefully controlled and the operating conditions (molar ratio of fatty acid to glycerol 0.1, air flow rate 25 ml/min., pH 7 commercial phosphate buffer) are optimized, yields as high as 100% can be easily achieved within 24 hours. Results have indicated that nearly 55% of increase in the reaction yield is obtained due to the foaming of the reaction mixture. Therefore, foaming conditions are essential in achieving high reaction yields. When increasing the fatty chain length from caprylic acid to myristic acid, we find reaction yields increase approximately by 30% and 50% in Lipozyme- and Lipase PS30-catalyzed reactions, respectively. Though these two lipases do not show difference in the product distribution, they do possess different selectivity toward stereo-positions. We have also found that in performing the unsaturated fatty acid (oleic acid) esterification, nearly 98% of reaction conversion can be achieved when lipase from Pencillium cyclopium, reactant molar ratio ((oleic acid) /(glycerol)) of 0.05, and the initial water content of 20% are employed. The preferrence toward the formation of the 1,2-diglyceride can be enhanced by regulating reaction conditions such as increasing the reaction temperature and the air flow rate. A quantitative study has shown that approximately 20 to 30% of acyl transfer between the diglyceride isomers taking place in foam systems is non-enzymatic. The enzyme addition further increases the intramolecular acyl migration by another 20 to 30%.