Promoting extracellular polymeric substances to alleviate phenol toxicity in Arthrospira platensis at high carbon dioxide concentrations

Carbon dioxide (CO2) capture combined with phenol degradation by cyanobacteria can sequester carbon back to biosphere and purify coal-chemical flue gas. It was found that intracellular damages caused by phenol was alleviated in Arthrospira platensis under high CO2 concentrations. A high CO2 concentration locally around the cells promoted secretion of extracellular polymeric substances (EPS). The stimulated humic acid-like organics (main ingredients in EPS observed by excitation-emission matrix fluorescence spectroscopy) with strong adhesive properties, which worked as protective barriers to limit phenol transportation into the cells and created a microenvironment suitable for cells growth. The activity of phenol hydroxylase released into extracellular matrix was increased by 112.7% to enhance extracellular phenol degradation under 99.99 vol% CO2. The decreased abundances of intracellular superoxide dismutase and malondialdehyde suggested that elevated CO2 level protected cells by alleviating phenol toxicity and regulating intracellular redox state. Furthermore, the effective quantum yield of photosystem II was promoted by reducing the damage on photosynthetic membranes under phenol stress, leading to an increased biomass productivity by 35.1% during the first four days under 99.99 vol% CO2. These results have provided a new approach to simultaneously improve carbon-capture and flue gas purification.