Hydrogen production by Escherichia coli during glucose fermentation: Effects of oxidative and reductive routes used by the strain lacking hydrogen oxidizing hydrogenases 1 (hya) and 2 (hyb)

Escherichia coli growth and hydrogen production in batch culture upon formate alone and with glycerol co-fermentation at different pHs

“…ORP kinetics and H 2 production were measured in bacterial batch cultures by the difference of pair of redox Pt and TieSi electrodes readings [12,16,21,36,38,41]. In the cells grown under fermentative conditions on glucose in the presence of 30 mM formate at pH 7.5 it was observed that H 2 production became mostly Hyd-3 dependent [21,22,32,34].…”

“…Bacteria from overnight culture were grown anaerobically in batch culture (glass vessels with plastic press-caps) in the liquid growth medium with the composition of 20 g L À1 peptone, 2 g L À1 K 2 HPO 4 , 5 g L À1 NaCl, 10 g L À1 glycerol and/or 10e50 mM formate at pH range of 5.5e7.5, and 37 C [9,12,16,21,22,34]. The pH was measured by a pH-meter with selective pH-electrode (HJ1131B, Hanna Instruments, Portugal) and adjusted with 0.1 M NaOH or 0.1 N HCl.…”

“…The operational direction of Hyd enzymes is variable; it depends on many factors, such as carbon (glucose or glycerol) source, and medium pH. Recently, it was shown that Hyd-1 and Hyd-2 operate in H 2 oxidation upon growth with glucose and H 2 formation modes upon glycerol fermentation [10,11,15,16]. Moreover, optimal activity of Hyd-1, encoded by the hya operon, was observed under anaerobic conditions, at acidic pH [17] and in the presence of formate [18], whereas Hyd-2, encoded by the hyb operon, was active under more reducing conditions [19] and at alkaline pH [17].…”