Influence of Different CO2 Concentrations on Microalgae Growth, alpha-Tocopherol Content and Fatty Acid Composition

A prerequisite for the growth of microalgae on an industrial scale is the optimization of cultivation conditions and the reduction of production costs. The nutrient elements, heat and carbon dioxide provided by flue gas can be used to increase biomass production. The aim of this study was to investigate the effects of different CO2 concentrations on algal strains with regard to biomass production, alpha-tocopherol content, fatty acid composition and fatty acid content. For this, we grew the three microalgae Coccomyxa sp., Desmodesmus sp. and Muriella terrestris that were isolated from two tufa-forming karstwater creeks characterized by high CO2 partial pressures. No significant differences in biomass production rate were observed when the cultures were gassed with air or 15% (v/v) CO2. However, cell growth increased substantially when 5% (v/v) CO2 was used. The content of alpha-tocopherol increased in the stationary phase compared to the logarithmic phase in all investigated strains. In contrast, it decreased significantly when the cultures were aerated with either 5% (v/v) CO2 or 15% (v/v) CO2. The saturation level of fatty acids was significantly higher in cultures aerated with CO2 in the stationary phase compared to the logarithmic phase. In contrast, it decreased in the stationary phase when the cultures were gassed with air. Fatty acid contents increased in the stationary phase compared to the logarithmic phase. It was also higher by gassing with 5% (v/v) CO2 and decreased when the cultures were aerated with air or 15% (v/v) CO2. When the biomass production rates were taken into consideration together with contents of alpha-tocopherol and total fatty acid, the productivity of both increased considerably when the cultures experienced gassing by a 5% (v/v) CO2.