Effects of culture medium salinity on the hydrocarbon extractability, growth and morphology of Botryococcus braunii

Here, we investigated the effects of culture medium salinity on the hydrocarbon extractability, growth and morphology of Botryococcus braunii strain Showa. At all tested salinities, the hydrocarbon recovery rate increased during the first or second cell division, which occurred within 7 days. Algal growth in modified Chu13 medium did not differ significantly from that in medium with 0.3% seawater salinity (0.3%SM) to which seawater (3.6%, salinity was 36 g L−1) was diluted. In contrast, culturing in 0.3% seawater salinity improved hydrocarbon extractability and shortened the time required for hydrocarbon extraction. This change supposed to be due to the decrease in the production of polysaccharides which prevent non-polar solvent from contacting hydrocarbons. Additionally, there was an increase in the colony sizes and flotation of the alga when cultured in 0.3% seawater salinity. The results of our experiments suggest that culturing B. braunii in a medium with the appropriate salinity can reduce the input energy and the costs incurred from harvest to hydrocarbon extraction without decreasing biomass production.