H2 PRODUCTION FROM CHEMOSTAT FERMENTATION OF GLUCOSE BY CLOSTRIDIUM-BUTYRICUM AND CLOSTRIDIUM-PASTEURIANUM IN AMMONIUM-LIMITATION AND PHOSPHATE LIMITATION

In ammonium-limitation (4.55 mM NH4+) at a dilution rate (D)=0.081 h-1, Clostridium butyricum produced 2 mol H2 per mol glucose consumed at pH 5.0, but at a low fermentation rate. At higher pH, important amounts of extracellular protein were produced. Phosphatelimitation (0.5 mM PO4-3) at D=0.061 h-1 and pH 7.0 were the best conditions tested for hydrogen gas production (2.22 mol H2 per mol glucose consumed) at a high fermentation rate. Steady-state growth at lower pH and with 0.1 mM PO4-3 resulted in proportional higher glucose incorporation into biomass and lower H2 production. C. pasteurianum in NH4+ limitation showed higher fermentation rates than C. butyricum and a stabilized H2 production around 2.08 (±0.06) mol per mol glucose consumed at various defined pH conditions, although the acetate/butyrate ratio increased to 1 at pH 7.0. The latter was also observed in phosphate-limitation, but here H2 production was maximal (1.90 mol. per mol glucose consumed) at the lowest pH (5.5) tested. © 1990 Kluwer Academic Publishers.