Effect of feed glucose and acetic acid on continuous biohydrogen production by Thermotoga neapolitana

This study focused on the effect of feed glucose and acetic acid on biohydrogen production by Thermotoga neapolitana under continuous-flow conditions. Increasing the feed glucose concentration from 11.1 to 41.6 mM decreased the hydrogen yield from 3.6 (±0.1) to 1.4 (±0.1) mol H2/mol glucose. The hydrogen production rate concomitantly increased until 27.8 mM of feed glucose but remained unaffected when feed glucose was further raised to 41.6 mM. Increasing the acetic acid concentration from 0 to 240 mM hampered dark fermentation in batch bioassays, diminishing the cumulative hydrogen production by 45% and the hydrogen production rate by 57%, but induced no negative effect during continuous operation. Indeed, throughout the continuous flow operation the process performance improved considerably, as indicated by the 47% increase of hydrogen yield up to 3.1 (±0.1) mol H2/mol glucose on day 110 at 27.8 mM feed glucose.