Prolongation of H2 production during mixed carbon sources fermentation in E. coli batch cultures: New findings and role of different hydrogenases

Hydrogen (H2) gas production in batch cultures was studied upon utilization of the mixture of glucose, glycerol and formic acid by Escherichia coli BW25113 wild type (wt) at pH of 5.5-7.5. At pH 7.5H2 was continuously produced during 240 h but at pH 6.5 and 5.5 it was detected till 168 h and 120 h, respectively. Specific growth rate (μ) of wt was the highest (1.05 h−1) at pH 6.5. Moreover, at pH 5.5 in hycE μ decreased by ∼4.14 fold compared to wt, suggesting major role of Hyd-3 in cell growth. H2 yield (8.8 mmol H2 L−1) was the highest at pH 7.5. In hybC H2 yield was increased ∼1.62 fold than in wt. These data might be applied for biomass and biohydrogen production from various organic wastes where mixtures of carbon sources are present.