Preparation Of Dialdehyde Starch And The Application To Immobilize Lipase

In this paper, the influences of different aldehyde contents on the physicochemical properties of DAS were investigated, immobilized lipase using DAS as carrier was first established and the effect of pretreatment of lipase before immobilization was studied. The preparation, separation process and physicochemical properties of L-ascorbyl oleate through transesterification of ascorbic acid and oleic acid in non-aqueous catalyzed by immobilized lipase was described. This study extended the application of DAS and domestic lipase, promoted the synthesis of immobilized lipase and L-ascorbyl oleate.(1) The process conditions of dialdehyde corn starch (DAS) with different aldehyde contents were investigated. It was founded that the aldehyde contents of DAS were24.35%,49.37%,71.10%and90.05%by controlling the amount of sodium periodate. The morphological, crystalline and thermal properties of DAS with different aldehyde contents were characterized and analyzed in detail.(2) On the basis of discussing the effect of temperature, reaction time, pH, the amount of carrier and olive oil, the preparation technology of immobilized lipase using DAS as carrier was optimized. It was indicated that conditions were pretreatment of lipase with100μL olive oil at37℃for30min, reaction time20h, temperature30℃, pH7.0and amount of DAS500mg. Finally, the stability of immobilized lipase was studied.(3) The optimal preparation process of L-ascorbyl oleate was established. The results indicated that the conditions were reaction time30h, reaction temperature35℃, amount of immobilized lipase80mg, amount of molecular sieve0.6g, the molar ratio of L-ascorbic acid to oleic acid was at1:5. Under this condition, L-ascorbyl oleate was obtained with a yield of38.2%. After the reaction, the result of thin layer chromatography showed that reaction product was composed of L-ascorbic acid, oleic acid and new substance.(4) The crude product of L-ascorbyl oleate which was separated and purified from the reaction solution was white solid. Meanwhile, we designed a solution for shortcomings of separation process of L-ascorbyl oleate. In the FT-IR spectra of L-ascorbyl oleate, the peaks at3397cm-1and2922cm-1,2852cm-1correspond to OH and C-H stretching, while the peaks at1734cm-1was the most characteristic band of C=O vibrations in L-ascorbyl oleate. The band at1599cm-1was due to the C=C band stretching of L-ascorbyl oleate. An intense band at824cm-1is present, which can be assigned to the RCH=RCH bound in the oleic acid. There were several discernible absorptions at1465,1292,719cm-1, which can be attributed to the structure of L-ascorbyl oleate.