Study On The Lipase-catalyzed Synthesis Of Glucose Esters In Organic Solvent

Sugar esters are non-ionic surfactants with carbon hydrate as hydrophilic group and fatty acids as hydrophobic group. They are widely used in the food, cosmetic, detergent and phar-maceutical industry because its high emulsifying capacity, nontoxicity, wide range of HLB value (1-16) and biodegradability. In additon , sugar esters have the effect of lubriacting ,detergency , foaming, anti-ageing, anti-crystallizing and anti- bacteria etc. Sugar esters are recommended food addiitives by FAO and WHO.The presented paper deals with the lipase catalyzed synhtesis of glucose esters, the purification of lauroyl monoesters, the optimization of batch synthesis of monoester and the measurement of surfactant properties of monoesters.A serie of glucose esters (lauroyl ester, cardamom ester, palmitic ester and stearic ester) were sythesized in actone solvent catalyzed by lipase NOVO435. The esters were identified by LC/MS, which showed that only monoester and diesters were synthesized. The optimal agent for thin layer chromatography (TLC) was tested and optimized, the final developing agent was the mixture of methylbenzene, acetic ester, methanol, and water with the volumic proportion of 10:40:4.5:1.0. This developing agent was applied to silica gel column chromatography as mobile phase for separation and purification of glucose monoesters. The purified monoesters were analyzed by HPLC-ELSD and LC-MS, confirming the purity of the monoester.The batch synthesis of lauroyl glucose was optimized.The influences of differnt factors ( organic solvent, temperature, time , molar ratio of fatty acid and glucose , the amount of lipase and molecular sieve etc.) were studied. The method of response surface analysis gave the optimal conditions in acetone as follows: the molar ratio of lauric to glucose 5:1, the amount of molecular sieve 68 g/L, the amount of lipase 30g/L, the shaking speed of the water bath 150r/min , the temperature 50℃, the reaction time 30 hours. The conversion ratio of the lauric glucose monoester reached 80.2% in this optimized condition.The surfactant properties such as the solubility , the HLB value , the emulsifing ability, foaming ability of four purified glucose monoesters were measured. The solubility was analysised by HPLC method, which showed that glucose monoesters had small solubility in water. The HLB value was studied by calculation and water titration , the HLB value of four monoesters confirmed by water titration were 11.3, 10.0, 9.3 and 8.5 respectively which were higher than the results obtained by calculation. The influences of temperature, concentration, different fatty acids on the emulsifing and foaming ability of glucose monoesters were also studied.