Cheese whey as substrate of batch hydrogen production: Effect of temperature and addition of buffer

The aim of this work was to evaluate the effect of buffer addition and process temperature (ambient and 35°C) on H₂ production in batch fermentation of cheese whey (CW). When the H₂ production reached a plateau, the headspace of the reactors were flushed with N₂ and reactors were re-incubated. Afterwards, only the reactors with phosphate buffer showed a second cycle of H₂ production and 48% more H₂ was obtained. The absence of a second cycle in non-buffered reactors could be related to a lower final pH than in the buffered reactors; the low pH could drive the fermentation to solvents production. Indeed a high solvent production was observed in non-buffered bioreactors as given by low ρ ratios (defined as the ratio between sum of organic acid production and sum of solvents production). Regarding the process temperatures, no significant difference between the H₂ production of reactors incubated at ambient temperature and at 35°C was described. After flushing the headspace of bioreactors with N₂ at the end of the second cycle, the H₂ production did not resume (in all reactors).