Immobilized Candida Antarctica B Lipase Catalyzed Synthesis Of Medium Chain Diacyglycerol And Sucrose Ester

Polyol ester is a nonionic surfactant, and it attracts the considerable attention recently, just for its safty, nutritional and multifunctional properties. The enzymatic synthesis of diacylglycerol (DAG) has been reported widely; but a systematical comparative study is still needed on the synthetic procedures based on batch and packed bed reactor, as well as the pathway via esterification and glycerolysis. In this work, the medium chain diacylglycerol and sucrose ester were synthesized using lipase Novozym 435 (from Candida antarctica) catalyzed, respectively.1. The esterification reaction was performed in a batch reactor first in order to select suitable reaction conditions. We found that petroleum ether was suitable for the esterification, which is considerable in case a solvent is needed to reduce the viscosity of reaction mixture without deactivating the lipase. However, solvent-free is an economical process and provided closer result as that in petroleum ether; therefore, no solvent was employed in following experiments. Metal ion did no effect to the catalytic activity of lipase; Different initial water content only changed the initial reaction rate; at the big open area (diameter was 29 mm), the conversion of caprylic acid was higher than normal, and the 4? molecular sieve was useless on dehydration. Besides, a suitable temperature and molar ratio had effects on the conversion of caprylic acid and the content of DAG in the reaction mixture. After the investigation, the optimum condition for the synthesis of diacyglycerol was that 30 mmol caprylic acid, 15 mmol glycerol, initial water content (5 wt% of glycerol), lipase of 250 U/g caprylic acid, open vessel (d=29 mm), 60 oC, 10 h, the highest conversion of caprylic acid was 94.21%, while the DAG content (45.07%) was obtained, with a yield of 43.76%. Furthermore, the microwave irradiation was applied to accelerate the esterification by 1.56 times.2. Reactions in the packed bed reactor usually provide better efficiency. However, many differences exist in the procedures executed in packed bed reactor and batch reactor, such as the heat transfer efficiency, reactant reserve time (represented as space velocity or appeared as the ratio of height to radio of the reactor) and mass transfer. As a comparison, the same esterification was carried out in a packed bed reactor as following investigation. Several reaction parameters, such as temperature, molar ratio of the reactants, charging method, enzyme loading, fill mode and ratio of height to diameter of the reactor on the esterification were studied. The conversion of caprylic acid and DAG content in the packed bed reactor reached 82.30% and 77.26%, with a DAG yield of 65.33%, catalyzed by 200 U Novozym 435 lipase/g caprylic acid, with 10% initial water content, 34 h-1 space velocity at 65 oC for 7 h. There was negligible loss in lipase activity in the packed bed reactor even after repeated use for 15 times. As a result, the packed bed reactor may provide higher DAG content with poorer caprylic acid conversion. If a well designed and scheduled constant feeding of caprylic acid was employed, better result could be expected.3. To consider the price of raw material and the cost of reaction, glycerolysis of medium chain triacylglycerols (GTCC) and glycerol was conducted in the presence of Novozyme 435 lipase. And t-butanol was found the only solvent suitable to the glycerolysis, for it can decrease the mass transfer resistance. In addition, it can be expected that the DAG content can be improved by raising the lipase loading or extending the reaction time. Under the optimum condition, glycerolysis in t-butanol yielded 21.04% MAG, 53.17% DAG, with a GTCC conversion of 74.21%. Besides, the microwave irradiation obviously accelerated the reaction rate as expected, and the DAG content is notably higher than that obtained via conventional heating.4. The pilot study was conducted on the synthesis of lauric acid sucrose ester, through the esterification of lauric acid and sucrose, catalyzed by lipase Novozym 435. And thin-layer chromatography combined with MS was used to analysis the products. After the investigation, the optimal condition for the synthesis of lauric acid sucrose ester was that molar ratio of sucrose to lauric acid was 1, quantity addition of t-butanol was 2.92 (w/w, substrate), 1700 U Novozym 435 lipase/g sucrose, 4% (w/w, substrate) buffer solution, 65oC, 24h, the conversion of lauric acid reached 22.17%. In addition, the microwave irradiation was applied again, and it could obviously accelerate the reaction rate as see before. But the effect of microwave irradiation became weaker as the time prolonged.