ABSTRACT The synthesis of enantiomerically pure d ‐amino acids is of growing interest due to their applications in pharmaceuticals, agrochemicals, and as building blocks in fine chemicals. While chemical synthesis methods are often environmentally unfriendly, enzymatic cascades offer a greener and more selective alternative. In this study, a one‐pot enzymatic cascade was established consisting of the soluble l ‐amino acid oxidase from Hebeloma cylindrosporum ( Hc LAAO4), a catalase, and a ( R )‐selective transaminase from Enterococcus italicus ( d ‐TA Ei ) for the conversion of l ‐amino acids into the corresponding d ‐enantiomers. The cascade efficiently produced a range of d ‐amino acids including phenylalanine, methionine, histidine, and tryptophan in enantiomerically pure form. Optimization of enzyme concentrations revealed that balanced loading of Hc LAAO4 and d ‐TA Ei achieves high conversions of up to 93% with >99% enantiomeric excess. Co‐immobilization of the enzymes on glutaraldehyde‐functionalized hexylamine (HA GA ) beads enhanced catalytic efficiency and speed, resulting in up to 80% conversion. Moreover, immobilization significantly affected the pH range of both d ‐TA EI and Hc LAAO4. These findings demonstrate the potential of combining broad‐substrate LAAOs with d ‐specific TA for sustainable and preparative‐scale production of d ‐amino acids.
Berelsmann et al. (Sun,) studied this question.