Effect and removal of bisphenol A by two extremophilic microalgal strains (Chlorophyta)

The effects and the removal efficiency of bisphenol A (BPA) on two extremophilic Chlorophyta strains, an alkaliphilic Picocystis and a thermophilic Graesiella , were assessed. BPA was shown to inhibit the growth and photosynthesis of both species, but to a greater extent for Graesiella . The growth IC 50 (4 days) was 32 mg L −1 for Graesiella and higher than 75 mg L −1 for Picocystis . Oxidative stress was induced in both strains when exposed to increasing BPA concentrations, as evidenced by increased malondialdehyde content. BPA exposure also resulted in an over-expression of antioxidant activities (ascorbate peroxidase, glutathione S -transferase and catalase) in Picocystis whereas they were repressed in Graesiella . Both species exhibited high BPA removal efficiency, reaching 72% for Picocystis and 52.6% for Graesiella at 25 mg L −1 . BPA removal was mostly attributed to biodegradation for both species. Overall, according to its extended tolerance and its removal capacity, Picocystis appeared to be a promising species for the BPA bioremediation even at high contamination levels.