Electrochemical enhancement of the accumulation of photosensitive components in anoxygenic phototrophic bacteria extracellular: A new insight into the preparation of degradable microbial photosensitizer for water treatment.

Extracellular polymeric substances (EPS) are promising biomaterials for environmental remediation, but their application is hindered by low production efficiency and limited pollutant degradation capacity. In this study, photosynthetic electron extraction enabled Rhodopseudomonas palustris (R. palustris) to efficiently produce EPS enriched with functionalized components. The enhanced EPS (0.2V-EPS), produced from electrically domesticated R. palustris, achieved an 82 % degradation rate of sulfamethoxazole (SMX) within 10 hours, an 18 % improvement compared to EPS produced under open-circuit conditions (OP-EPS). Mechanistic analysis revealed that photosynthetic electron extraction enriched EPS with photosensitive molecules, including tryptophan, humic acid, fulvic acid, which significantly promoted the generation of reactive species. The primary reactive species identified were triplet-excited EPS (³EPS*), ¹O₂, and •OH, with ¹O₂ as the dominant contributor to SMX degradation. The steady-state concentration of ³EPS*, ¹O₂, and •OH increased by 73 %, 34 % and 16 %, respectively, compared to the control. Structural modifications of 0.2V-EPS, including increased hydrophilicity, electronegativity, and aromaticity, enhance its physicochemical properties, thereby facilitating interactions with pollutants. Furthermore, an 88 % reduction in biofilm polysaccharides diminished free radical scavenging activity, promoting the generation of reactive species. This study provides a sustainable strategy for enhancing EPS functionality and offers insights into the metabolic regulation of microorganisms for pollutant degradation.