Effects of hydrostatic pressure and supercritical carbon dioxide on the viability of Botryococcus braunii algae cells

In bio-based industries, Botryococcus braunii is identified as a potential resource for production of hydrocarbons having a wide range of applications in chemical and biopolymer industries. For a sustainable production platform, the algae cultivation should be integrated with downstream processes. Ideally the algae are not harvested, but the product is isolated while cultivation and growth is continued especially if the doubling time is slow. Consequently, hydrocarbons can be extracted while keeping the algae viable. In this study, the effects of pressure on the viability of B. braunii cells were tested hydrostatically and under supercritical CO2 conditions. Viability was determined by light microscopy, methylene blue uptake and by re-cultivation of the algae after treatments to follow the growth. It was concluded that supercritical CO2 was lethal to the algae, whereas hydrostatic pressure treatments up to 150 bar have not affected cell viability and recultivation was successful.