Combination of multi-enzyme expression fine-tuning and co-substrates addition improves phenyllactic acid production with an Escherichia coli whole-cell biocatalyst

•Whole-cell catalytic ability improved by regulating the expression of multi-enzymes.•Co-substrates addition could increase cofactor concentration and cell stability.•Wheat straw hydrolysate was a promising cost-effective co-substrate.•Established whole-cell catalytic system produced 54.0 g/L of phenyllactic acid. The aim of this study was to develop an environmentally safe and efficient method for phenyllactic acid (PLA) production using whole-cell cascade catalysis with l-amino acid deaminase (l-AAD), lactate dehydrogenase (LDH), and formate dehydrogenase (FDH). The PPA titer was low due to relatively low expression of LDH, intermediate accumulation, and lack of cofactors. To address this issue, ribosome binding site regulation, gene duplication, and induction optimization were performed to increased the PLA titer to 43.8 g/L. Then co-substrates (glucose, yeast extract, and glycerol) were used to increase NADH concentration and cell stability, resulting that the PLA titer was increased to 54.0 g/L, which is the highest reported production by biocatalyst. Finally, glucose was replaced with wheat straw hydrolysate as co-substrate to decrease the cost. Notably, the strategies reported herein may be generally applicable to other whole-cell cascade biocatalysts.