Regioselective Lipase-Catalyzed Synthesis Of Sucrose-6-Acetate

Sucrose-6-acetate is essential intermediate for selectively preparing sucralose. Compared with traditional chemical synthesis, lipase-catalyzed synthesis of Sucrose-6-acetate has the advantages of high regioselectivity, simple process of preparation and mild reaction environment. This dissertation was based on medium engineering. The selectivity of lipases were investigated in the organic, microaqueous and aqueous two-phase systemsFirst, in the organic phase, four lipases which were Lipozyme TL IM (T), Novo 435 (N435), Candida lipase (CRL) and porcine pancreatic lipase (PPL) were used as catalysts to synthesize sucrose-6-acetate in 12 organic solvents. And three kinds of reactions were determined.1) With 2-butanol as reaction medium and Lipozyme TL IM as the catalyst, sucrose-6-acetate was synthesized.2) With tert-amyl alcohol as reaction medium and Lipozyme TL IM as the catalyst, sucrose-6-acetate was synthesized.3) With tert-amyl alcohol as the reaction medium and Candida rugosa lipase as the catalyst, sucrose-6-acetate was synthesized.Secondly, effect of buffer type and water content on lipase-catalyzed synthesis of sucrose-6-acetate was studied in microaqueous system. Three kinds of reactions were determined.1) In 2-butanol with 0.6% H2BO3-Na2B4O7 · 10H2O buffer solution, with Lipozyme TL IM as the catalyst, sucrose-6-acetate was synthesized by transesterification of sucrose with vinyl acetate.2) In tert-amyl alcohol with 1.0% Tris-HCl buffer solution, with Lipozyme TL IM as the catalyst, sucrose-6-acetate was synthesized by transesterification of sucrose with vinyl acetate.3) In tert-amyl alcohol with 0.8% Tris-HCl buffer solution, with Candida rugosa lipase as the catalyst, sucrose-6-acetate was synthesized by transesterification of sucrose with vinyl acetate. The lipase catalytic activity and selectivity were different between in organic system and in microaqueous system. In 2-butanol with 0.6% H2BO3-Na2B4O7 · 10H2O buffer solution, Lipozyme TL IM catalytic activity was about 10 times as high as that in 2-butanol. In tert-amyl alcohol with 1.0%Tris-HCl buffer solution, Lipozyme TL IM catalytic activity was about 5.7 times as high as that in tert-amyl alcohol, and the selectivity increased by 30%. In tert-amyl alcohol with 0.8% Tris-HCl buffer solution, Candida rugosa lipase catalytic activity was about 5.7 times as high as that in tert-amyl alcohol.Finally, in the buffer/tert-amyl alcohol two-phase system, Candida rugosa lipase-catalyzed synthesis of sucrose-6-acetate was investigated. The optimum reaction conditions were determined by single factor experiments. The buffer solution was Tris-HCl, Tris concentration was 0.1mmol/ml, vinyl acetate:sucrose was 3:1, initial pH was 7.0, tert-amyl alcohol volume content was 30%, reaction temperature was 35 ℃, and reaction time was 4 h. Under the reaction conditions, the yield and selectivity of sucrose-6-acetate respectively were 35.3% and 55.6%. In Tris-HCl buffer solution/tert-amyl alcohol two-phase system, Candida rugosa lipase catalytic activity was about 10 times as high that in microaqueous system, but the selectivity decreased.