Thermosynechococcus sp. CL-1 (TCL-1) as an efficient cyanobacterium in CO₂ fixation, C-phycocyanin production, and removal of Cd and Pb

Photosynthetic microorganisms achieve a tremendous CO₂ fixation rate and heavy metal removal. This study assessed the performance of Thermosynechococcus sp. CL-1 for CO₂ fixation, heavy metals (Cd and Pb) removal, and C-phycocyanin production. The tests were conducted under various light intensities (500–2,000 µE/m²/s) and the concentration of additional Cd and Pb. Cultivation was carried out in a flat-panel photobioreactor at a temperature of 50 ^oC for 12 h for examination of CO₂ fixation rate, heavy metal removal, and phycocyanin production. Increasing light intensity promoted TCL-1 growth performance and only a slight decline was caused by the heavy metals. Supply of 2,000 µE/m²/s light intensity with 5 MF, 2.5 mg-Cd/L, and 0.5 mg-Pb/L achieved CO₂ fixation rates of 118.1±12.5, 106.9±30.1, and 114.1±26.9 mg/L/h, respectively. Total Cd removal was presented under 2,000 µE/m²/s light intensity, but only 36–67% Pb removal was achieved. Removal of heavy metals was dominated by the bio-adsorption process by the functional groups on the surface of the cells. Besides, heavy metals also reduced C-phycocyanin production by TCL-1. Thus, TCL-1 can be a potential candidate for simultaneous CO₂ fixation and heavy metal removal.