ABSTRACT
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 41.6â¯mM decreased the hydrogen yield from 3.6 (±0.1) to 1.4 (±0.1)â¯molâ¯H2/mol glucose. The hydrogen production rate concomitantly increased until 27.8â¯mM of feed glucose but remained unaffected when feed glucose was further raised to 41.6â¯mM. Increasing the acetic acid concentration from 0 to 240â¯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)â¯molâ¯H2/mol glucose on day 110 at 27.8â¯mM feed glucose.