Study On Enzymatic Synthesis Of Sucrose-6-ester

Sucrose-6-acetate is the key intermediate when we synthesizing the super-sweetener sucralose. Sucralose is a perfect and competitive sweetener as its high sweetness, strong security, powerful stability, pure sweet as well as no energy. In the study of the synthesis of sucrose esters, more research was focus on the biocatalyst synthesis because of its mild reaction condition and high regioselectivity. In this paper, synthesis of sucrose-6-acetate using lipase to catalyze acyl donor and sucrose in non-aqueous medium was studied. The product sucrose-6-acetate was separated and purified from the reaction catalyzed with lipase. Moreover, the synthesize sucralose applying the way of enzyme-chemical as well as synthesizing sucrose-6-laurate using the similar catalysis system were also tried.Firstly, the mensuration of sucrose-6-acetate with High Performance Liquid Chromatography was tested. The analysis condition was following:HPLC (Agilent 1100 series), column (Diamonsil C185μm250×4.6 mm); detector (Alltech Inc.):Evaporative Light Scattering Detector, mobile phase was methanol:water (10:90,V/V), the flow rate was 0.8mL/min, the column temperature was 35℃, and the injection volume was 1μL. This method could effectively distinguish sucrose-6-acetate and sucrose-4-acetate and its isomers.Secondly, the factors influence on synthesis of sucrose-6-acetate using lipase as catalysis in non-aqueous were investigated. Results showed that lipase Lipozyme TLIM was an efficient catalyst in the transesterification of vinyl acetate and sucrose, in which DMSO and tert-butyl alcohol used as the non-aqueous medium. The optimized reaction conditions were:volume ratio of DMSO to tert-butyl alcohol 1:4, mole ratio of vinyl acetate to sucrose 10:1, and the amount of immobilized lipase Lipozyme TLIM was 1.0 IUN/(mg-sucrose). The yield of sucrose-6-acetate could reach 89.3% when the transesterification of 0.06 mmoL/mL sucrose concentration was performed at 30℃and 200 r/min rotate speed for 9 h.After transesterification, the solids and low-boiling point liquid were removed by centrifugation and evaporating. Crude sucrose-6-acetate was deposited by adding triple volume of methylene chloride. Crystal sucrose-6-acetate was got through column chromatography, concentration and crystallization, its degree of purity could come up to 99.7%. This product was identified as sucrose-6-acetate by HPLC-MS, IR, NMR, etc.Preparation of sucralose was tried from sucrose to sucrose-6-acetate by enzymatic, as well as chlorinated and deacetylation with chemical means. The total yield was about 31.7%.Preparation of sucrose-6-laurate was also attempted using the similar reaction system that used in synthesis of sucrose-6-acetate. In the medium of DMSO/tert-butyl alcohol, the yield of sucrose-6-acetate could reach 97.1% under the reaction conditions were temperature at 30℃,200 r/min of rotation speed,9 h of reaction time, and which the dosage of Lipozyme TLIM was 1.0 IUN/(mg-sucrose) and the mole ratio of lauric acid vinyl ester to sucrose was 10 times. The result showed that the system was applicability to the preparation of sucrose-6-ester by enzymatic.