Synechococcus elongatus BDU 130192, an Attractive Cyanobacterium for Feedstock Applications: Response to Culture Conditions

Marine cyanobacteria are attractive organisms as feedstock for bioethanol and biotechnological applications. Previously, a marine cyanobacterial strain Synechococcus elongatus BDU 130192 was identified which can accumulate high polyglucan levels without the need to resort to N-deprivation. In this study, among the three different temperatures (30, 34, and 38 °C) tested, the highest biomass accumulation and total carbohydrate occur at 34 °C. The biomass and total carbohydrate increased with increasing light intensities, while protein, chlorophyll, and carotenoid contents were reduced. The best growth occurred at 1.8% NaCl concentration, even though the strain could grow well until 5.8% NaCl. Among the different concentrations of CO2 tested, the best growth occurred at 5% CO2 in the air. NaNO3 gave the best growth, though the cells were able to grow well on urea and NH4Cl too. Tripling the concentration of either N or P in the medium led to a significant increase in growth rate. The strain does not require the addition of vitamin B12 for growth, and about 90% flocculation could be achieved in an hour with the addition of chitosan. High productivities of 0.5 g/L/day of biomass and 0.23 g/L/day of carbohydrates could be reached in a 3-L photobioreactor (PBR) bubbled with air. This work shows many unique properties of this strain such as high carbohydrate productivity, ability to tolerate high light intensities and high concentrations of salt and CO2, and efficient flocculation. These properties make Synechococcus elongatus BDU 130192 an attractive candidate as a feedstock for bioethanol and biotechnological applications.