Physiological response and oxidative transformation of 2,2′,4,4′-tetrabromodiphenyl ether (BDE-47) by a Chlorella isolate

Polybrominated diphenyl ethers (PBDEs) are ubiquitous, toxic and persistent pollutants in environments. Microalgae frequent exposed to these pollutants may possess defense mechanisms against their toxicity and have the ability to metabolize them, thus are important in bioremediation. This study investigated the mechanism of a Chlorella isolate to degrade BDE-47, a common PBDE congener, and its subcellular responses to BDE-47 stress. Results showed that 86–98% of the spiked BDE-47 was removed by Chlorella via adsorption, uptake and metabolism. BDE-47 was metabolized through debromination, hydroxylation and methoxylation. The oxidative transformation to hydroxylated products was the initial and main metabolic process. BDE-47 induced the production of hydrogen peroxide (H₂O₂) in cell wall, plasma membrane and chloroplast of Chlorella, and such increase was regulated by nicotinamide adenine dinucleotide phosphate oxidase and H₂O₂-producing peroxidases (PODs). The activity of H₂O₂-consuming PODs and the content of glutathione were also significantly enhanced to detoxify the oxidative stress.