Evaluation of the phycoremediation potential of microalgae for captan removal: Comprehensive analysis on toxicity, detoxification and antioxidants modulation

Abstract

Captan is one of the most widely used organochlorine fungicides, its frequent application contaminates both terrestrial and aquatic ecosystems and negatively affects their key ecological processes. This study demonstrated the toxicity and efficient removal of captan by two different taxonomic species; the green microalga Scenedesmus obliquus and cyanobacterium Nostoc muscorum. After a week of exposure to mild (15 mg/L) and severe (30 mg/L) captan doses, the intracellular captan uptake, degradation and metabolic regulation of captan detoxification were studied. Compared to N. muscorum, S. obliquus accumulated more captan, but efficiently degraded it into two safe eco-friendly by-products; phthalic acid and 1,2,3,6-tetrahydro phthalimide. S. obliquus showed less decrease in cell growth, photosynthesis activity and related parameters including Chla content and activity of PEPC and RuBisCo enzymes. Captan at the severe dose induced oxidative damage particularly in N. muscorum, as expressed by the high levels of H2O2, MDA, NADPH oxidase and protein peroxidation. Both species invested glutathione-s-transferase enzyme in captan detoxification however, induction of antioxidant defence system e.g. ascorbate and glutathione cycle was more pronounced in S. obliquus which could explain its tolerance ability. This study provided a better understanding of the environmental risks of captan and introduced S. obliquus as a promising captan phycoremediator.