Effective asymmetric bioreduction of ethyl 4-chloro-3-oxobutanoate to ethyl (R)-4-chloro-3-hydroxybutanoate by recombinant E. coli CCZU-A13 in [Bmim]PF6-hydrolyzate media

It was the first report that the concentrated hydrolyzates from the enzymatic hydrolysis of dilute NaOH (3 wt%)-soaking rice straw at 30 degrees C was used to form [Bmim]PF6-hydrolyzate (50:50, v/v) media for bioconverting ethyl 4- chloro-3-oxobutanoate (COBE) into ethyl (R)-4-chloro-3-hydroxybutanoate[(R)-CHBE] (>99% e.e.) with recombinant E. coli CCZU-A13. Compared with pure glucose, the hydrolyzates could promote both initial reaction rate and the intracellular NADH content. Furthermore, emulsifier OP-10 (20 mM) was employed to improve the reductase activity. Moreover, Hp-beta-cyclodextrin (0.01 mol Hp-beta-cyclodextrin/mol COBE) was also added into this bioreaction system for enhancing the biosynthesis of (R)-CHBE from COBE by E. coli CCZU-A13 whole-cells. The yield of (R)-CHBE (>99% e.e.) from 800 mM COBE was obtained at 100% in the [Bmim]PF6-hydrolyzate (50:50, v/v) media by supplementation of OP-10 (20 mM) and Hp-beta-CD (8 mM). In conclusion, an effective strategy for the biosynthesis of (R)-CHBE was successfully demonstrated. (C) 2016 Elsevier Ltd. All rights reserved.