Hydrogen and organic acid production from dark fermentation of cheese whey without buffers under mesophilic condition

BioH(2) production from cheese whey (CW) was evaluated in two acidogenic reactors, UASB and structured fixed-bed (FB), without pH adjustment, under mesophilic conditions, and OLR of 25-90 g COD/L.d. Stage 1 was conducted as a control experiment using sucrose. BioH(2) production occurred under pH < 3.0 with maximum yields of 5.8 and 3.0 mol H-2/mol sucrose(consumed) for UASB and FB reactors, respectively. In Stage 2, CW was the only substrate and a negligible bioH(2) production was observed. Nevertheless, a maximum lactic acid concentration of 9.6 g/L was obtained, indicating that pH adjustment can be non-essential for lactic acid production from CW. In Stage 3, a strategy to enrich hydrogenogenic biomass was conducted by initially feeding the reactors with sucrose and gradually replacing it by CW. This strategy brought better bioH(2) results compared to Stage 2, but it could not bear over the long-term, as non-hydrogen producing bacteria became predominant. (AU)