Cascade synthesis of D-phenyllactic acid using amorphous metal-organic framework-modified Escherichia coli

Abstract

D-phenyllactic acid is an important medical intermediate and a potential green preservative. Due to its extensive use and high demand, there has been significant research interest in developing efficient synthesis methods. In this study, we aimed to efficiently produce D-phenyllactic acid from L-phenylalanine through a two-step cascade reaction using a coupled catalytic system consisting of two bacteria strains (E. coli/pET28a-lrldh and E. coli/pET28a-ladd2). To enhance the stability of this catalytic system, we encapsulated the two recombinant E. coli strains with amorphous ZIF-90, which was thoroughly characterized using various methods including SEM, FT-IR, TGA, XRD, XPS, and CLSM analysis. Compared to free cells, the immobilized living materials (amorphous ZIF-90@E. coli) showed good stability in harsh environments and superior recyclability. When applied to the production of D-PLA, the amorphous ZIF-90@E. coli system achieved a yield of 9.00 g/L and a conversion of 89.4 %. This successful coupling catalysis from L-phenylalanine to D-PLA indicates the potential of aZIF-90@E. coli for biosynthesis of D-phenyllactic acid in future industrial applications.