Enzymatic Production of D-Amino Acids

Optically pure amino acids are of increasing industrial importance as chiral building blocks for the synthesis of food ingredients, pharmaceuticals, drugs, and drug intermediates. Highly stereoselective enzymatic processes have been developed to obtain either D- or L-amino acids from D,L-mono-substituted hydantoin derivatives. The initial enzymatic reaction step of D,L-mono-substituted hydantoin hydrolysis is catalyzed by a D-hydantoinase after the subsequent racemization of L-isomer to D-isomer and leads to N-carbamoyl-D-amino acid. It is further hydrolyzed to D-amino acid by D-carbamoylase. Agrobacterium radiobacter and some other Agrobacterium species discussed in this chapter posses both the enzymes viz. D-hydantoinase and D-carbamoylase. In this chapter, D-p-hydroxyphenylglycine production from D,L-p-hydrox-yphenyl hydantoin has been studied in more detail. The purpose of this chapter is to provide the comprehensive idea to the readers directly from producing biocatalyst, analytical methods, harvesting the D-amino acids, and its characterization.