Study On Asymmetric Reduction Of Acetophenone Using Photosynthetic Bacteria In Non-aqueous Medium

With optical pure chiral compounds market demand is growing, using biocatalyst will dive chiral compounds, chemical synthesis of precursor substances or racemize derivatives into a single enantiomers products in medicine, materials, spices, pesticides and fine chemical products production which will become increasingly important. People have come to realize that biocatalyst in asymmetric biological transformation of the applications of the huge potential, but previous studies limited in water phase system, it has many shortcomings,such as low solubility of substrate, substrate is more harmful to biocatalyst and recycling or separation of product is difficult, which greatly hindered the development of industrial applications. However, the above disadvantages all can overcome through non-aqueous phase media biological catalytic reaction. In recent years, activity and stability of enzymes and cells have get greatly breakthrough progress in non-aqueous phase media system.Currently people advocate organic synthesis process green and cut off the cost of the economy, which foster development of non-aqueous phase media application system. Biocatalysis in non-aqueous phase system has become an important subject, which have been successfully used in a variety of organic synthesis and kinetic resolution reaction.Based on one individual strain of the laboratory,called photosynthetic bacteria-Rhodobacter sphaeroicles and no oxygen produced, thus established a model of catalyzed acetophenone produce chiral alcohols, on the basis of the study in water phase system previously, this paper discusses the mechanism of photosynthetic bacteria in organic solvent, ionic liquids and perfluorocarbons system in biocatalytic asymmetric reduction. Through the research we found that non-aqueous phase media system have their advantages compare with water phase system, photosynthetic bacteria in which needed to maintain catalytic activity and stability, the reaction selectivity and product yield has obviously improved. In addition, this paper is also pilot study on the treatment of photosynthetic bacteria permeability.The results show that the0.2%CTAB (Hexadecyl trimethyl ammonium Bromide) process made the photosynthetic bacteria in the production rate increase, and its corresponding changes in selective, produced R-phenylethanol, ee value could up to100%.Main contents are as follows:1. Constructing water-organic solvent system and researching asymmetric reduction by immobilized photosynthetic bacteria. Examine the metabolic activity retention of photosynthetic bacteria in different organic solvents, determine the best reaction conditions through activity of photosynthetic bacteria, organic phase volume fraction and substrate concentration, the results show that optimal reaction conditions for asymmetric reduction:aqueous:organic3:2, substrate concentration25mmol/L, pH7.5, reaction time48h. The mainly product for S-phenylethanol.2. Choose a kind of hydrophobic ionic liquid [BMIM][PF6] and two hydrophilic ionic liquids [BMIM][BF4] and [EMIM][EtSO4], constructing the catalytic reaction system that discusses the reduction mechanism of immobilized photosynthetic bacteria as biocatalyst. From growth activity of photosynthetic bacteria in ionic liquids and distribution coefficient of substance, we choose hydrophilic ionic liquid [HMIM][EtSO4] for research. We found that ionic liquid volume fraction is15%, and substrate concentration35mmol/L, the yield of product could amount to80.3%, much higher than traditional organic phase and aqueous phase system. Meanwhile, recycling of reaction medium and biocatalyst could still keep its basic vitality.3. Choose two common perfluorocarbons called perfluorohexane and perfluorooctane together with buffer, Which were used to construct asymmetric reduction system, through study we found that under the optimal reaction conditions; the yield of product could up to78.6%,enantioselectivity value of S-phenylethanol more than95%. And compared with perfluorohexane, perfluorooctane was more application prospect and could be recycled under mild conditions.4. Choose CTAB as a treatment reagent for permeability of photosynthetic bacteria, through measuring treatment concentration, freezing-thawing time and processing times, determined the optimal treatment combinations:processing bacteria15min using0.2%CTAB, freezing-thawing time12h, repeated operation two times, permeable cells in buffer solution system used for biological transformation reaction, the yield of product increases,the product was R-phenylethanol and ee value could up to100%.