Fig. 4
Optimization studies and reductive amination employing mutant M3-2. Influences of temperature (a), pH (b), NH4+ concentration (c), and NAD+ concentration (d) on the reductive amination of 2-OPBA using M3–2. Reductive amination of 2-OPBA in presence of 0.2–0.5 M substrate (e) and application of a combination of substrate fed-batch with product removal (f). Conversion of 2-OPBA was determined by monitoring the concentration of 2-OPBA in the reaction mixture with HPLC analysis. Absolute configuration and ee value of l-HPA were established and calculated by comparing the obtained values with those from authentic reference material after derivatization. The biotransformation experiment was performed in triplicate, and error bounds represent ± sd