To examine the dependence of H2 evolution on external acetate, glucose and incubating pH, P. subcordiformis cells were incubated in S-deprived medium in dark for 32 h (flushed with N2 for 5 min at the start) and then illuminated under light.
H2 evolution was very sensitive to the medium pH (Fig. 4). Low H2 production was observed at pH below 6 and above 10.
Maximum H2 evolution was achieved at pH 8, which is about 7.8- and 5.4-fold higher than that at pH 6 and pH 10, respectively (Fig. 4).