P113: Photosynthetic accumulation of carbon storage compounds under CO2 enrichment by the thermophilic cyanobacterium Thermosynechococcus elongatus

The growth characteristics of Thermosynechococcus elongatus on elevated concentrations of CO₂ were examined in a photobioreactor. Cultures were also analyzed for their ability to sequester CO₂ in compounds with potential application as biofuels and biomaterials, such as polyhydroxybutyrate (PHB), lipids, and glycogen.  T. elongatus was able to grow on up to 20% CO₂. The maximum productivity and CO₂ fixation rates were 0.09±0.01 mg ml^-1 d^-1 and 0.17±0.01 mg ml^-1 d^-1 respectively, for cultures grown on 20% CO₂. The maximum amount of carbon sequestered was 1.15 g L^-1 over the course of the 9 day experiment. Lipids, PHB’s, and glycogen accounted for 60% of the total biomass carbon in cultures grown on atmospheric CO₂ levels (no supplemental CO₂), but only accounted for 40% of the total biomass carbon in cultures grown on 5-20% CO₂. Lipid content was around 20% (w/w) under all experimental conditions while PHB content reached 14.5% (w/w) in cultures grown on atmospheric CO₂ and decreased to around 2.0% (w/w) at 5-20% CO₂. Glycogen levels did not vary significantly and remained around 1.4% (w/w) under all test conditions.