Multifunctional Thermosynechococcus sp. CL-1 cultivation in swine wastewater for nutrients utilization, CO₂ fixation, and C-phycocyanin production

Background: Combination of the CO₂ fixation and wastewater treatment process can be simultaneously and efficiently conducted using cultivation of photosynthetic microorganisms along with generation of byproducts as the alternative benefit. Method: In this study, a cyanobacterium, Thermosynechococcus sp. CL-1 (TCL-1), has been cultivated in unsterilized swine wastewater for assessment on nutrients (N and P) removal, CO₂ fixation rate, and accumulation of C-phycocyanin. Experiment was conducted using a flat panel photobioreactor and under supply of various light intensities of 500-2,000 µE/m²/s. Significant findings: The presence of ammonium and phosphate in the swine wastewater were favorable to support the growth of TCL-1. TCL-1 eliminated almost all the ammonium during 8 h of experimental test under illumination of higher light intensity (1,000 or 2,000 µE/m²/s). Similarly, compared to other tested light intensities, 2,000 µE/m²/s resulted in greater phosphate utilization. However, 500 µE/m²/s light intensity indicated a higher total phosphorus utilization. Besides, addition of dissolved inorganic carbon (DIC) in the swine wastewater resulted the highest CO₂ fixation rate of 145.1±12.1 mg/L/h. C-phycocyanin as a valuable pigment compound was accumulated by TCL-1 with concentration of 4.9 %dwc, productivity of 6.46±0.7 mg/L/h, and in the purity index range of 0.79-0.86.