The Biosynthesis Of Octenyl Succinic Anhydride Modified Starch And Saccharide Ester By Yeast Displayed Lipase

The paper systematically reviews the concepts of lipase, yeast surface display, glycolipids, SSOS and their application in various industries for the later theoretical basis of the experimental operation. This study try to lipase-catalyzed synthetize suger esters by the yeast surface display.In the experimental section, firstly the orthogonal optimization of the freeze-dried preservative for the yeast whole cell CALB has been studied. The composite preservative, 10% skim milk,6% trehalose,2% vitamin C,1.5% sodium glutamate, was identified, which can make the relative activity up to 88.32% after freeze-drying. In the freeze-drying process, the impact of skim milk was bigger than Vitamin C. The least impact is trehalose. After studying the enzymatic properties of the whole-cell lipase, we found that it had good thermalstability. it remained more than 50% activity at 50℃for 6h. The optimum temperature and pH value were 40℃and pH6.5. After analyzing the esterification and hydrolysis, it can be inferred that the lipase-catalyzed reaction may share the same active center.Whole-cell lipase could catalyze the synthesis of starch octenyl succinic acid ester in the semi-fixed starch state. It had different effects for the substitution degree and reaction efficiency, such as the temperature and time of gelatinization, the added amount of OSA and lipase and the pH value, temperature and time of the reaction. Based on single-factor test, the orthogonal test of esterification also was researched. The best combination had been idetified:gelatinization of 65℃15min,8% OSA,0.6% lipase, reaction temperature 40℃, time 30min, which could make the starch ester of 0.023 substitution degree. Modern analytical techniques investigated octenyl succinic acid groups connected with the starch molecules in the form of ester bonds. The crystal structure had no change. The shape and surface structure of starch granules were severely damaged. Compared with the original, the product has good flocculability, transparency and emulsion stability.In other glycolipid synthesis, whole-cell lipase could catalytize the synthesis of sucrose laurate and glucose laurate in the solvent system of tert-butanol and acetone. Using thin-layer chromatography, preliminary isolation and identification of the reaction mixture had been carried out. Separate agent of sucrose laurate was toluene:ethyl acetate:methanol:water=10:40:4.5:1.0. And Separate agent of glucose laurate was the literature method (chloroform:methanol:acetic acid:water=81:9:8:2). More than traditional chemical synthesis, the reaction temperature reduced significantly, with inhibition of byproduct. Because lipase firmly fixed on the cell surface by chemical action, its operational stability, heat resistance, reusability has been improved.