Hydrogen photoproduction by growing cultures of Anabaena variabilis and A. azollae did not occur under air+CO2 or argon+CO2 atmospheres at saturating light but did take place under argon alone. It was shown that CO2 inhibited photoproduction of H2 as a result of the photosynthetic production of O2 whereas photoreduction of C2H2 by these cyanobacteria was not inhibited by O2 concentrations up to 20% in the assay gas phase. In contrast to the wild type of A. variabilis and of A. azollae, H2 photoproduction by the hydrogenase-impaired mutant A. variabilis PK84 showed only a slight dependence on O2 concentration. Thus, in the wild-type Anabaena the decrease in the observed rate of H2 evolution at elevated O2 concentrations could be the result of an increase in hydrogenase-mediated uptake of H2 via an oxyhydrogen reaction. Copyright (C) 1998 Federation of European Microbiological Societies.
Tsygankov, A. A., Serebryakova, L. T., Rao, K. K., & Hall, D. O. (1998). Acetylene reduction and hydrogen photoproduction by wild-type and mutant strains of Anabaena at different CO2 and O2 concentrations. FEMS Microbiology Letters, 167(1), 13–17. https://doi.org/10.1016/S0378-1097(98)00361-9