Wang, P; Zhou, LM; He, JY; Zu, L; Sun, LM
A hydrophobic ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM] PF6) was used as the solvent for asymmetric bioreduction of ethyl acetoacetate (EOB) to prepare optically active ethyl (R)-3-hydroxybutyrate (R-EHB) with Pichia membranaefaciens Hansen cells. The suitable reaction conditions, such as [BMIM] PF6 content, pH value, co-substrate concentration, reaction temperature, substrate concentration, cell concentration and reaction time, were investigated, respectively. The results show that these factors obviously influence the yield and the optical purity of the prepared R-EHB. The optimum values of [BMIM] PF6 content, pH value, co-substrate concentration, reaction temperature, substrate concentration, cell concentration and reaction time are 20%, 7.8, 80 g·L-1, 30°C, 0.5 mol·L-1, 280 g·L-1 and 18 h, respectively. Under above optimal conditions, the maximum yield of 72.2% and 70.3% of e.e. of the prepared product were obtained, respectively. The results also demonstrate that the inhibition effect of EOB on R-EHB yield can be markedly reduced by the use of [BMIM] PF6 and the bioconversion is more efficient in [BMIM] PF6-buffer biphasic system than that in monophasic aqueous system or hexane-buffer biphasic system.
