Enhancing biohydrogen production of the alkalithermophile Thermobrachium celere

In this study the effect of different buffering agents, pH control and N2 sparging on biohydrogen production in Thermobrachium celere was investigated in batch cultivations. Among the tested buffers, none was able to prevent the medium acidification resulting in a premature interruption of the hydrogen production. Controlling the pH helped to sustain the growth, the complete substrate consumption and the H2 production. However, in these conditions the increase of H2 partial pressure induced a partial metabolic shift towards ethanol production resulting in a decreased H2 yield. Analysis of formate accumulation during growth suggests that this compound might play a relevant role in the anabolic routes in T. celere. When frequent N2 sparging was applied for H2 removal, together with pH control, the H2 yield was remarkably enhanced from 2.26 to 3.53 mol H2/mol glucose, and the maximum H2 production rate and specific H2 production rate reached 41.5 mmol H2/l/h and 142.3 mmol H2/h/g, respectively. This result suggests that under proper conditions T. celere is able to produce hydrogen at high yield and production rate.

► Effect of buffering agents, pH control and N2 sparging on biohydrogen production in Thermobrachium celere.► Medium acidification and elevated H2 concentration negatively affected the hydrogen production. ► Combining pH control and N2 sparging was effective to enhance the hydrogen production in T. celere.► H2 yield of 3.53 mol H2/mol glucose and maximum H2 production rate of 41.5 mmol H2/l/h were achieved. ► Highest H2 production rate observed in thermophilic species.