Production of phenyllactic acid by using whole-cell recombinant Escherichia coli

D- lactate dehydrogenase was expressed in recombinant Escherichia coli BL21( DE3),the expression conditions and bioconversion medium were optimized for the production of PLA with whole- cell transformation.Single factor experiments and orthogonal experiments were used to optimize induction conditions and the transformation conditions with the engineered whole- cells transformation. The optimized induction condition for D- ldh expression was IPTG 0.2mmol / L and inducing for 4h at 25℃ and OD6001.2,the optimized batch reaction conditions in phosphate buffer( p H7.0) were: 8g / L PPA,20 g / L glucose,20 g / L( dry cell weight),1% Tween- 80,37℃,200 r / min for 0.5h with PLA production of 4.91 g / L and conversion ratio of 56%.Based on the above optimized conditions,fed- batch fermentation was conducted by intermittent feed PPA and glucose. After 6h transformation,the final PLA concentration reached 17.23 g / L with the conversion ratio of 54%. Results showed that PPA was efficiently transformed into PLA through engineered E.coli BL21( DE3) / p ET28a- D- ldh.This study not only showed a good industrial application prospect,but also laid a foundation for metabolic engineering of E. coli for the production of PLA.