Analysis of photosynthetic pigments pathway produced by CO2-toxicity- induced Scenedesmus obliquus

The coal-to-gas process produces carbon dioxide, which increases global warming, and its wastewater treatment gen-erates sludge with high organic toxicity. Scenedesmus obliquus is a potential solution to such environmental problems, and photosynthetic pigments are the focus of this study. The optimal concentration of CO2 for the growth of Scenedesmus obliquus was found to be 30 % after increasing the concentration of CO2 (0.05 %-100 %). The accumula-tion of photosynthetic pigments during cultivation could reach 31.74 +/- 1.33 mg/L, 11.21 +/- 0.42 mg/L, and 5.59 +/- 0.19 mg/L respectively, and the organic toxicity of sludge extract could be reduced by 44.97 %. Upregulation of A0A383VSL5, A0A383WMQ3, and A0A2Z4THB7 as photo systemic oxygen release proteins and propylene phosphate isomerase resulted in oxygen-evolving proteins in photosystem II, electron transport in photosystem I, and intermedi-ates in carbon fixation. This is achieved by increasing the intracellular antennae protein and carbon fixation pathway, allowing Scenedesmus obliquus to both tolerate and fix CO2 and reduce the organic toxicity of sludge. These findings provide insights into the innovative strategy underlining the fixation of CO2, treatment and disposal of industrial resid-ual sludge, and the enhancement of microalgal biomass production.