Fig. 3

Studies on the enantioselectivity of the hydantoinase from A. crystallopoietes toward pNO₂PheDU ((R/S)-4a). a Chiral separations in order to determine the enantioselectivity of the hydantoinase pNO₂PheDU ((R/S)-4a) as substrate in whole cell biocatalysis with recombinant E. coli JM109. Solid line separation of 2 mM NCarbpNO₂ βPhe standard ((R/S)-5a), dashed line separation of NCarbpNO₂ βPhe ((R/S)-5a) after 24 h biotransformation. b Concentrations of the (S)- and (R)-enantiomer (empty circles and filled circles) and enantiomeric excess (filled triangles) during the reaction progress. Reactions and measurements were carried out in triplets and error bars show the standard deviations of the means. Detection by HPLC Agilent 1200 system [Chiralpak QN-AX column, 257 nm, 30 °C, 0.3 mL/min; isocratic mobile phase: 98 % (v/v) methanol (0.2 % v/v ammonium formate) and 2 % (v/v) acetic acid (0.2 M, adjusted to pH 6 with ammonia)]