Whole Cell‐Based Cascade Biotransformation for the Production of (S)‐Mandelic Acid from Styrene, L‐Phenylalanine, Glucose, or Glycerol

Abstract ( S )‐Mandelic acid is a useful and high value chemical with many synthetic applications, but its synthesis often requires the use of toxic cyanide. Here, we report the development of several cyanide‐free methods to prepare ( S )‐mandelic acid via cascade biotransformation. Enhanced production of ( S )‐mandelic acid from styrene via 4‐step enzyme cascades was achieved with Escherichia coli (A‐M1_R‐M2) cells, giving 118–144 mM (18–21.9 g/L, 72–79% yield) product. The process was scaled up to 1.5 L to produce 140 mM (21.3 g/L) of ( S )‐mandelic acid in 70% yield. A strategy with the recycling and reuse of Escherichia coli cells, unreacted substrate, and organic solvent was developed to enhance the productivity of ( S )‐mandelic acid through repeated batches, affording 190 mM (95% yield) and 328 mM (82% yield) product in two and four batches, respectively. ( S )‐mandelic acid was also produced from bio‐derived L‐ phenylalanine via 6‐step enzyme cascades. Biotransformation of L‐ phenylalanine with Escherichia coli (LZ37) cells expressing all enzymes for the reactions gave 160 mM ( S )‐mandelic acid in 80% yield. Moreover, ( S )‐mandelic acid were synthesized from glycerol or glucose via L‐ phenylalanine biosynthesis pathway and the 6‐step enzyme cascade. Coupling of Escherichia coli (NST74‐Phe) with Escherichia coli (LZ37) enabled the sustainable production of 63 mM (10 g/L) or 52 mM (8 g/L) ( S )‐mandelic acid from renewable feedstocks glycerol and glucose, respectively. magnified image