Potential for biodiesel production and carbon capturing from Synechococcus Elongatus: An isolation and evaluation study

The freshwater cyanobacterium Synechococcus elongatus was isolated from a Ramsar hot spring in the north of Iran and cultivated in BG11 medium. For genetic identification and purification, due to the presence of symbiotic bacteria, axenic culture was prepared by using an antibiotic, UV radiation and serial dilution. It was found that combination of serial dilution and UV radiation at 280 nm for 10 min and light intensity of 730 lx is an effective method for preparation of axenic culture. Using 16s-rRNA along with morphological comparisons, the cyanobacteria was identified as Synechococcus elongatus. Sixteen days after cultivation, the cell density was measured at 1.63±0.0758 g/L and the biomass productivity was estimated at 0.116 g/L/day. The lipid content and lipid productivity were 18.5% of dry cell weight and 0.02 g/L/day, respectively. This study aims mainly at removal efficiency of high amount of carbon dioxide (CO2) with a high cyanobacterial growth rate. For this purpose, 2, 5 and 10% CO2 in inlet air with flow rates of 32, 52 and 72 mL/min were investigated. The highest growth rate was observed at the flow rate of 72 mL/min with 2% CO2. The highest CO2 removal efficiency (100%) was achieved at input flow rate of 32 mL/min and 2% CO2 concentration. However, when the inlet gas flow rate was 52 mL/min with 2% CO2 in the inlet air, in addition to having a higher growth rate, the removal efficiency reached about 96%. Thus, this condition is introduced as an optimum operating condition.