Microalgae strategy in anoxic atmospheres with various CO2 concentrations – Environmental and (astro)biotechnological perspectives

Abstract

The current study examines the survival strategy of microalgae in closed systems with anoxic atmospheres and the possibility of creating an oxygenic atmosphere through the photosynthetic management of solar radiation. The complete absence of CO2 seems to be addressed initially by the catabolism of cellular organic matter through the respiratory process (possibly by using NO2 instead of O2), which produces CO2. This CO2 supports the photosynthetic process, which produces O2, part of which is used primarily for the O2 enrichment of the atmosphere and the rest for the respiratory procedure and biomass production. Microalgae showed a tolerance to exogenously supplied extreme CO2 concentrations (1 %–40 %) in an anoxic atmosphere and displayed a significantly higher photosynthetic activity compared with that of microalgae cultures grown in an oxygenic atmosphere. This response of microalgae to extreme high CO2 concentrations under anoxic conditions enhances immediately the level of O2 in the atmosphere as well as the culture growth without any stress responses. Since this strategy of microalgae is particularly effective in converting CO2 into O2 in CO2-rich atmosphere, it could help to combat the greenhouse effect by integrating microalgae cultures into toxic gas detoxification systems with extremely high CO2 concentrations. The ability of microalgae to turn hostile atmospheres swiftly into O2-rich atmospheres could be used in the future for the continuous recycling of the atmosphere of human settlement on other planets. Additionally, the increased microalgae biomass under these conditions is an ideal module for important (astro)biotechnological applications.