Effect of growth conditions on advantages of hup- strain for H2 photoproduction by Rubrivivax gelatinosus

H-2 photoproduction by growing cultures of hup(-) mutant and parental strain RL2 of Rubrivivax gelatinosus was compared. We checked the influence of different substrates, presence of air and N-2, culture shaking, inoculum concentrations. At low inoculum concentration, hur strain demonstrated significant advantage over the parental strain in microaerobic conditions, while under N-2-Ar atmosphere it was lower and vanished in anaerobic conditions (Ar only). This advantage was evident when using substrates with low degree of reduction (malate and succinate). Culture shaking under microaerobic conditions and in presence of N-2 completely prevented H-2 production by both strains. The high inoculum concentration inhibited H-2 production under microaerobic conditions and in presence of N-2, unlike to anaerobic conditions. With inoculum concentration increase, H-2 production decreased not gradually but stepwise which means some metabolic shift. H-2 production by hup strain seems to be more tolerant to air traces than by parental strain. (C) 2017 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.