Chemoenzymatic synthesis of d(−)phenylglycine using hydantoinase of Pseudomonas desmolyticum resting cells

We screened 125 Pseudomonas strains from our culture collection for the production of hydantoinase activity using dl-phenylhydantoin as a substrate. Pseudomonas desmolyticum NCIM 2112 was found to be the best hydantoinase (dihydropyrimidinase E.C. 3.5.2.2) producer. The enzymatic reactions were carried out using 18–20-h grown cells in nutrient broth and 5-phenylhydantoin as the substrate. Optimization studies for the biotransformation reaction were performed to increase product yield. The optimum pH and temperature for d(−) N-carbamoylphenylglycine production were 9.5 and 30°C, respectively. Biotransformation under these alkaline conditions allowed the complete conversion of 27.0 g l −1 of dl-phenylhydantoin to 26.5 g l −1 of N-carbamoylphenylglycine within 24 h, with a molar yield of 90%. The hydantoinase involved in this biotransformation process was strictly d-stereospecific, because the product isolated was pure d(−) N-carbamoylphenylglycine. This pure product was further chemically converted to d(−)phenylglycine using nitrous acid with an 80% chemical yield. Thus, the overall conversion efficiency of dl-5-phenylhydantoin to d(−)phenylglycine was found to be 65–68%.