Asymmetric Reduction of Acetophenone by Candida Valida under Compressed CO2
|Keywords||High pressure CO2 Asymmetric reduction Catalytic reaction of microbial cells Candida valida Acetophenone (R)-α- phenyl ethanol|
Microbial cell asymmetric reduction of prochiral substances synthesis of chiral compounds with high efficiency and high stereoselectivity characteristics, chiral synthesis has become the most promising methods. Changing environment in which the reaction medium, but also the improvement of chiral synthesis is an important research direction. This work was chosen rough shape Candida Candida valida asymmetric reduction of acetophenone as a model reaction to study the high-pressure CO 2 environmental impact of the reaction. First investigated by high-pressure CO 2 cells treated Candida valida under atmospheric pressure asymmetric reduction of acetophenone reactions. The results showed that, with untreated cells, the treated cells can efficiently Candida valida catalyzed asymmetric reduction of acetophenone, generate R-enantiomer excess of α-phenylethyl alcohol, but the reaction ee of only 70 ~ 80%. By examining the cell processing time, pressure and temperature on the subsequent response of pressure, found that as the extension of treatment time, the increase in pressure and temperature increased, the yield of the product will significantly decreased, while showing slightly ee of changes. Secondly, the effects of high pressure CO 2 environment Candida valida asymmetric reduction of acetophenone properties. The effects of substrate concentration, cells, reaction temperature, pressure, pH value of the reaction system, the auxiliary substrate and the stirring effect on the reaction, and found that Candida valida in the high pressure CO 2 environment still have Good ability of asymmetric reduction of acetophenone. The optimum reaction conditions: reaction system 20mlPBS (0.2mol / L, pH7.0) buffer, acetophenone initial concentration 24.4mmol / L, the auxiliary substrate is glucose 0.1g/ml, cell dosage 0.4g / ml, at 6.0MPa, 30 ℃ under the conditions of reaction 30h. α-phenyl ethanol yield of up to 90%, ee value of 80 to 90%. Compared with the reaction pressure was allowed to stand, α-phenylethyl alcohol increases the yield of 30 ~ 40%, ee value is also increased by about 10%. Finally, try to control the high pressure CO 2 environment Candida valida asymmetric reduction of acetophenone stereoselectivity investigated thermal pretreatment of cells, changing the cell culture conditions and methods such as bacteria, discovered aerobic fermentation The cells in the logarithmic growth phase showed a better response stereoselectivity; thermal pretreatment of cells did not make the reaction ee value increased; Candida valida than bread yeast catalyzed reaction product of higher yields, which is obtained S-enantiomer excess of α-phenyl ethanol. High CO 2 environment reuse Candida valida three times, the reaction product yield and ee values ??have decreased significantly.