Effect of carbon dioxide and temperature on H2 producing cultures of the extreme thermophile, Caldicellulosiruptor saccharolyticus

摘要

Carbon dioxide could replace nitrogen gas as stripping gas to relieve cultures of theextreme thermophile, Caldicellulosiruptor saccharolyticus, of the inhibition by H2,provided that the pH is kept below 7.0. Above this pH, ≥77 mM sodium bicarbonatewill be introduced as an extra salt burden to the culture. High concentrations ofsolutes contribute to the inhibition of H2 production. The underlying cause is mostprobably osmolality. As a consequence, using CO2 as stripping gas might lower themaximum allowable acetate concentration in the culture, and therefore theproductivity. With CO2, lower yields of biomass and hydrogen were obtained,whereas the maximum specific growth rate was not affected. In a thermodynamicstudy an estimations of the activation enthalpies were made for both hydrogenproduction and thermal deactivation, being 45.9 kJ/mol and 160.1 kJ/mol,respectively. Hydrogen production showed a wider temperature range (estimated 40 -90 °C) than growth (49.6 – 85.7 °C).