Acetylene reduction and hydrogen photoproduction by wild-type and mutant strains of Anabaena at different CO2 and O2 concentrations

Abstract

Hydrogen photoproduction by growing cultures of Anabaena variabilis and A. azollae did not occur under air+CO P or argon+CO P atmospheres at saturating light but did take place under argon alone. It was shown that CO P inhibited photoproduction of H P as a result of the photosynthetic production of O P whereas photoreduction of C P H P by these cyanobacteria was not inhibited by O P concentrations up to 20% in the assay gas phase. In contrast to the wild type of A. variabilis and of A. azollae, H P photoproduction by the hydrogenase-impaired mutant A. variabilis PK84 showed only a slight dependence on O P concentration. Thus, in the wild-type Anabaena the decrease in the observed rate of H P evolution at elevated O P concentrations could be the result of an increase in hydrogenase-mediated uptake of H P via an oxyhydrogen reaction. z

Ultrastructure of the fresh water cyanobacterium Anabaena variabilis SPU 003 and its application for oxygen-free hydrogen production

“…With the increasing light, the amount of oxygen available for the reaction increases and thus no hydrogen was seen above a certain period of illumination. Tsygankov et al [8] have reported similar results with A. variabilis ATCC 29413 and A. variabilis PK84. The results are strongly supported from the fact that on providing increasing concentration of O 2 in the vials incubated in the dark, hydrogen production decreased.…”

High rates of photobiological H2 production by a cyanobacterium under aerobic conditions

“…In filamentous, heterocystforming diazotrophic strains, this is largely ascribed to the activities of an uptake hydrogenase enzyme system that is functionally closely associated with nitrogenase and oxidizes the H 2 produced 3, [33][34][35] . It has been shown that wild-type Anabaena variabilis cells can generate H 2 only under an argon atmosphere, whereas its uptake hydrogenase mutants PK84 and AVM13 can produce H 2 aerobically 27,[36][37][38] . A recent study also demonstrated H 2 production (~25 µmol per mg of Chl.h) from the vegetative cells of wild-type Anabaena variabilis under nitrogen atmosphere when strict anaerobic conditions are maintained 39 .…”

Hydrogenases and Hydrogen Metabolism of Cyanobacteria

“…The gas phase (214), the age and density of the culture, and the composition, pH, and temperature of the growth medium are also crucial to the final result. Most of the research on cyanobacterial hydrogen production has been carried out with nitrogen-fixing strains (31,55,106,111,166,205,206). In these organisms, the net hydrogen production is the result of hydrogen evolution catalyzed by nitrogenase and of hydrogen consumption catalyzed mainly by an uptake hydrogenase.…”