ABSTRACT
The enantioselective resolution of (R,S)-2,3-dichloro-1-propanol ((R,S)-DCP) to (S)-DCP by whole cells of a recombinant Escherichia coli expressing halohydrin dehalogenase (HHDH) activity was limited by product inhibition. To solve this problem to improve the productivity of (S)-DCP, an n-heptane-aqueous biphasic system was adopted in this work. The influential operational parameters including phase volumetric ratio, buffer pH and reaction temperature were optimized. Under the optimal reaction conditions, significant improvements of substrate concentration and biocatalyst productivity (375 mM and 7.64 mmol (S)-DCP g(-1) cell) were achieved in this n-heptane-aqueous biphasic system compared with aqueous single-phase system (150 mM and 2.97 mmol g(-1)cell). The scale-up biosynthesis of (S)-DCP was successfully performed in a 2-L stirred reactor, resulting in a 128.8 mM (S)-DCP with enantiomeric excess of 99.1% and average productivity of 2.07 g (S)-DCPL(-1) h(-1), respectively.
Subject(s)
Chlorohydrins/chemical synthesis , Heptanes/chemistry , Water/chemistry , Biocatalysis , Bioreactors , TemperatureABSTRACT
Biotransformation of 1,3-dichloro-2-propanol (DCP) to epichlorohydrin (ECH) by the whole cells of recombinant Escherichia coli expressing halohydrin dehalogenase was limited by product inhibition. To solve this problem and improve the ECH yield, a biotransformation strategy using resin-based in situ product removal (ISPR) was investigated. Seven macroporous resins were examined to adsorb ECH: resin HZD-9 was the best. When 10 % (w/v) HZD-9 was added to batch biotransformation, 53.3 mM ECH was obtained with a molar yield of 88.3 %. The supplement of the HZD-9 increased the ECH volumetric productivity from 0.5 to 2.8 mmol/l min compared to without addition of resin. In fed-batch biotransformation, this approach increased ECH from 31 to 87 mM. These results provide a promising basis for the biosynthesis of ECH.
