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

Abstract

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, α-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 α-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 α-tocopherol and total fatty acid, the productivity of both increased considerably when the cultures experienced gassing by a 5% (v/v) CO₂.

Keywords:

• carbon dioxide gassing
• content of α-tocopherol
• content of total fatty acid
• fatty acid composition
• microalgae biomass production rate

Acknowledgments

We thank Sandra Pusch for cultivation of the investigated strains, Prof. Dr. Wolfgang Bilger and Jens Hermann for the tocopherol analysis. Kathrin Lindner is acknowledged for assisting during cultivation as well as for the analysis of tocopherol and fatty acids. Dr. Katrin I. Mohr is acknowledged for providing the three strains investigated in this study; their establishment was made possible through a grant of the Deutsche Forschungsgemeinschaft (DFG) awarded to TF (FR 905/13-2, 3). NR and TF acknowledge the assistance in maintenance of the studied strains at the SAG culture collection by Ilse Kunkel, Marlis Heinemann, Hella Timmermann and Dr. Maike Lorenz.

Funding

This paper is publication # 56 of the Research Unit 571 “Geobiology of organo- and biofilms” funded by the German Research Foundation (DFG-FOR 571, FR905/13). FR905/13). This research was supported by Biomassekompetenzzentrum Schleswig-Holstein.