The Study On Asymmetric Reduction Of 2'-chloro-acetophenone Catalyzed By Immobilized Yeast Cells In Buffer-Ionic Liquids Biphasic System

Ionic liquids are salts consisting of positively charged cations and negatively charged anions.They are liquids below 100℃.Depending upon their nontoxicity,low volatility,nonflammability,high thermal stability,recycle using and the substituent for other volatile organic solvents,they are widely used in processes of separation, chemical reaction and biocatalysis.For their specific properties.Ionic liquids are called "green solvent".Chiral compounds have been widely applied in pharmaceuticals,food,pesticide and chemical industry due to their special optical activity.With the progress in pharmacology of chiral pharmaceuticals and the strict regulation on the application of new racemic drug in recent years,the research and development of chiral pharmaceuticals have become the new focus and direction.Enantiomerically pure alcohols are important intermediates for synthesis of pharmaceuticals.Asymmetric reduction of pro-chiral ketones catalyzed by microorganism or the oxidoreductase in the cell has been an important method of synthesis enantiomerically pure alcohols.In this work,using 2'-chloroacetophenone as the mode substrate,the reaction characteristics of the reduction of aromatic ketone by whole cell of yeast in Ionic liquid/aqueous biphasic system were studied.The conversion was improved by optimizing reaction conditions.By the comparation of different system,it was proved that the ionic liquid [BMIM]PF₆/aqueous biphasic system is more suitable for whole cell of yeast's reduction than other organic solvent/aqueous biphasic system and pure aqueous phase system,especially when the substrate concentration was high.Under the substrate concentration of 64.72 mmol/L(10g·L^-1)and catalyzed by free cells,the conversion was 54.5%after optimizing,nearly 300%as that in the pure water system.The production e.e.value was 98.6%.After being immobilized by Sodium alginate-CaCl₂,the yeast cell's catalysis activity was increased.Based on this conclusion,the reaction conditions were optimized.The optimal conditions were:Immobilized cell's content of 360 g/L; V_I.L/V_aqof 1:15;buffer pH of 7.2;shaker frequency of 200rpm;reaction time of 45h; reaction temperature of 30℃;adding glucose of 10%twice.Under these conditions, the maximum conversion was 75.4%with the substrate concentration of 64.72 mmol/L.The production e.e.value was around 99.1%.