Fig. 4

Optimization of the cell factory for 5-hydroxyectoine production. a The E. coli strain FF4169 carrying plasmid pMP41 (the ectD gene from P. stutzeri A1501) was cultivated for 24 h in MMA containing ampicillin and 0.4 M NaCl in the presence of 10 mM ectoine (growth of the cultures is plotted on the right Y-axis) (black dots). The ectoine (grey) and 5-hydroxyectoine (red) content of the supernatants were examined via HPLC analysis (plotted on left Y-axis). b Samples from cultures of strain FF4169 (pMP41) propagated in MMA with 0.4 M NaCl and 15 mM ectoine were taken after 16, 18, 20, 22 and 24 h of growth and the ectoine (grey) and 5-hydroxyectoine (red) content of the supernatant was analyzed by HPLC. c The E. coli strain FF4169 (pMP41) was grown for 24 h in MMA containing ampicillin and 0.4 M NaCl in the presence of different ratios of ectoine and 5-hydroxyectoine. The amounts of both compounds in the supernatant were quantified by HPLC analysis; ectoine (grey) and 5-hydroxyectoine (red) bars. All values shown in parts (a), (b), and (c) are the means and standard deviations of at least two independent cultures