Simultaneous 17β-estradiol degradation, carbon dioxide fixation, and carotenoid accumulation by Thermosynechococcus...

Thermosynechococcus sp. CL-1 (TCL-1) has a high potency to utilize CO₂ under extreme conditions including high temperature, alkaline condition, and the occurrence of 17β-estradiol (E2). In this study, TCL-1 cultivation with E2 addition in the range of 0-20 mg/L was combined with various growth arrangements (light intensity and dissolved inorganic nitrogen/DIN level). After 120 h cultivation, the 1.0 mg/L E2, 200 µmol photons/m²/s light intensity, and 5.8 mM available nitrogen performed the best growth with 4.58 ± 0.18 mg/L/h biomass productivity, 94.9 ± 3.3% total estrogen removal, and 11.41 ± 0.11 mg/L/h CO₂ fixation rate. Estrogen degradation was mainly carried out by biodegradation route which started from E2 conversion into estrone/E1 and with only 4-6% influence from the abiotic factors. Compared with the accumulated zeaxanthin, β-carotene was dominantly generated with a productivity of 0.043 ± 0.019 mg/L/h. Therefore, TCL-1 cultivation is an efficient strategy for simultaneous CO₂ fixation, estrogen removal, and carotenoid accumulation as valuable byproducts.