Fig. 4

Growth (a) and H₂ production (b) of the FO strain in a bioreactor under oxic conditions omitting the addition of reducing agent Na₂S, autoclaving, and inert gas purging. The wild-type (circles) and FO (inverted triangles) strains were cultured under oxic (open symbols) or anoxic (closed symbols) conditions in a 3-L bioreactor with 4 g L⁻¹ of yeast extract and 400 mM sodium formate as a substrate. Cell growth was monitored by measuring the optical density at 600 nm (OD₆₀₀). pH was adjusted to 6.1–6.2 using 2 N HCl containing 3.5% NaCl or 0.5 M citric acid containing 4% NaCl. Error bars indicate standard deviation of three independent cultures of the FO strain, and the data for the wild-type strain under anoxic conditions were adapted from previously reported data [23]