Cofactor self-sufficient whole cell biotransformation for 2-phenylethanol and D-phenyllactic acid

Whole cell biotransformation is a green and sustainable technology for chemical compounds production which may replace chemical process. The efficiency of the biocatalysts is often affected by the insufficient cofactor supply, redox imbalance or co-product inhibition. Here, we presented a self-sufficient whole cell biocatalysis strategy for 2-phenylethanol (2-PE) production by metabolic engineered Escherichia coli. Firstly, heterogeneous Ehrlich pathway was constructed in Escherichia coli for conversion of L-phenylalanine to 2-PE. Secondly, to balance the cofactors (L-glutamate/2-oxoglutarate and NAD(P)⁺/NAD(P)H ) of the system, coupling of glutamate dehydrogenase to transaminase and cascading with alcohol dehydrogenase were applied to make a self-sufficient whole cell biotransformation with redox balance and cofactor balance. Thirdly, zeolite was added in the resting buffer system to reduce the ammonium accumulation, which contributed to driving the reactions to 2-PE biosynthesis. By combining these manipulations of strain and process engineering, the yield of 2-PE was significantly increased and 5.86 g/L (48 mM) of 2-PE was achieved in 12 h with a conversion rate of 96 mol%. By in-situ product removal of 2-PE, 7.4 g/L of 2-PE was accumulated in 6 h bioconversion. Furthermore, the strategy of self-sufficient biotransformation was extended and applied in bioconversion of D-phenyllactic acid (D-PLA) from L- phenylalanine. The biotransformation efficiency of D-PLA was improved dramatically and the highest productivity of D-PLA (3.32 g/L/h) was achieved. This work offers a rationale to resolve cofactor and redox imbalance problem and demonstrates the feasibility of self-sufficient whole cell biotransformation strategy for enhanced production for chemicals.