초록
<P><B>Abstract</B></P><P>(<I>S</I>)‐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 (<I>S</I>)‐mandelic acid <I>via</I> cascade biotransformation. Enhanced production of (<I>S</I>)‐mandelic acid from styrene <I>via</I> 4‐step enzyme cascades was achieved with <I>Escherichia coli</I> (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 (<I>S</I>)‐mandelic acid in 70% yield. A strategy with the recycling and reuse of <I>Escherichia coli</I> cells, unreacted substrate, and organic solvent was developed to enhance the productivity of (<I>S</I>)‐mandelic acid through repeated batches, affording 190 mM (95% yield) and 328 mM (82% yield) product in two and four batches, respectively. (<I>S</I>)‐mandelic acid was also produced from bio‐derived <I>L‐</I>phenylalanine <I>via</I> 6‐step enzyme cascades. Biotransformation of <I>L‐</I>phenylalanine with <I>Escherichia coli</I> (LZ37) cells expressing all enzymes for the reactions gave 160 mM (<I>S</I>)‐mandelic acid in 80% yield. Moreover, (<I>S</I>)‐mandelic acid were synthesized from glycerol or glucose <I>via L‐</I>phenylalanine biosynthesis pathway and the 6‐step enzyme cascade. Coupling of <I>Escherichia coli</I> (NST74‐Phe) with <I>Escherichia coli</I> (LZ37) enabled the sustainable production of 63 mM (10 g/L) or 52 mM (8 g/L) (<I>S</I>)‐mandelic acid from renewable feedstocks glycerol and glucose, respectively.</P>