Simultaneous photoinactivation of Microcystis aeruginosa and photocatalytic degradation of microcystin-LR by erythrosine-based photosensitizer

The simultaneous control of toxic cyanobacterial blooms and degradation of microcystins (MCs) remains a critical challenge for environmental risk reduction. Herein, we demonstrate the novel application of erythrosine (ERY), an Food and Drug Administration (FDA)-certified food additive, as a potent photoactive agent for concurrent control of cyanobacterial blooms and removal of microcystin-LR (MC-LR) contaminants. ERY treatment achieved effective growth inhibition of Microcystis aeruginosa. Mechanistic studies, including reactive oxygen species (ROS) quenching experiments, revealed that ERY-generated ROS caused comprehensive damage to cellular structures and photosynthesis systems. Notably, the ERY-treated samples showed a significantly greater reduction in extracellular MC-LR content compared to conventional H2O2 treatment, confirming its superior microcystin degradation efficiency. The degradation pathways of MC-LR were elucidated through LC-MS/MS analysis, with reactive sites confirmed by electrostatic potential (ESP) mapping and Fukui function calculations. Furthermore, ecotoxicological evaluation using Lemna minor and ERY decomposition kinetics (95.6% within 4 days) confirmed its minimal phytotoxicity and reduced secondary pollution risk. These findings position ERY as a promising and environmentally benign photosensitizer for harmful algal bloom mitigation.