Effect of physico-chemical parameters on biohydrogen production and growth characteristics by batch culture of Rhodobacter sphaeroides CIP 60.6

In this paper, Rhodobacter sphaeroides CIP 60.6 strain was newly used for the biohydrogen production in a perfectly shaken column photobioreactor, grown in batch culture under anaerobic and illumination conditions, to investigate the effects of some physico-chemical parameters in microbial hydrogen photofermentation. Luedeking-Piret model was considered for the data fitting to find out the mode of hydrogen generation and the relationship between the cell growth and hydrogen production. The results show that, both growth cells and resting cells can produce hydrogen at light intensities greater or equal to 2500 lux, however, at the weak intensities hydrogen is a metabolite associated to growth. Growth rate and hydrogen production rate increase with the increasing of light intensity. Moreover, hydrogen production rate become higher in stationary phase than that in logarithmic phase, with the enhancement of light intensity. Maximum hydrogen production rate obtained was 39.88 ± 0.14 ml/l/h, at the optimal conditions (4500-8500 lux). Modified Gompertz equation was applied for the data fitting to verify the accuracy and the agreement of the model with experimental results. It is revealed that, in the modified Gompertz equation, the lag time represents time for which hydrogen production becomes maximal, not the beginning time of hydrogen production. The stop of stirring reduced hydrogen production rate and created unstable hydrogen production in reactor. The pH ranges of 7.5 ± 0.1 were the favorable pH for hydrogen production.