The time-series evaluation of biohydrogen production by photosynthetic bacteria under fluctuating illumination pattern

In recent years, world climate change and global warming have been big issues. One of the solutions is to use renewable energies; however, renewable energies have an intermittent nature. In the case of photovoltaic arrays, the intermittency is mainly caused by fluctuating irradiation from sunlight due to clouds. In this study, biohydrogen production from photosynthetic bacteria was focused for the use of fluctuating sunlight irradiation. Previous researches have revealed some characteristics of biohydrogen production, and these results enable one to expect that photosynthetic bacteria have fluctuating light tolerance of biohydrogen production, in which the bacteria are able to produce biohydrogen continuously under fluctuating light irradiation. There have been quite a few studies to evaluate time-course changes of biohydrogen production under fluctuating irradiation, and therefore time-course evaluations have been performed. A 10-min light/dark illumination pattern was set for the fluctuating irradiation and the magnitude of the fluctuation was used to evaluate the fluctuation of the hydrogen production rate and irradiation light. The results indicated that the fluctuation was 0.22 times smaller through the photosynthetic bacteria. The results of this study indicate that photosynthetic bacteria have fluctuating light tolerance. Biohydrogen production, having fluctuating light tolerance, would be useful for realistic use of sunlight energy as renewable energy.