Carbamazepine toxicity and its co-metabolic removal by the cyanobacteria Spirulina platensis

Bioremediation of pharmaceutical-contaminated wastewater using microalgae has attracted increasing attention. Cyanobacteria, which are important prokaryotic microalgae, are widely distributed in different water environments, and have the advantages of simple culture and a fast growth rate. However, studies on either the toxicity of pharmaceutical contaminants (PhCs) to cyanobacteria or the removal of PhCs by cyanobacteria are scarce. In this study, carbamazepine (CBZ) and Spirulina platensis were selected as model PhCs and cyanobacteria, respectively. CBZ (>1 mg/L) had toxicity effects on S. platensis, showing maximal growth inhibition (34.0%) at 100 mg/L after 10 days of cultivation. At CBZ 25 mg/L S. platensis showed a trend similar to that of eukaryotic microalgae in increasing superoxide dismutase and catalase activities and content of chlorophylls, carotenoids, carbohydrates, and lipids. These results indicated that S. platensis had a similar protective mechanism to CBZ toxicity as that of the eukaryotic microalgae. Increasing CBZ concentration (50-100 mg/L) significanctly decreased these biochemical characteristics and photosynthetic activity owing to the serious damage of the structure and function of S. platensis. However, with increasing cultivation lime, the growth and photosynthetic activity of S. platensis recovered from the toxicity of CBZ. S. platensis showed a maximum of 30.97 +/- 1.30% removal of CBZ (1 mg/L), mainly through biodegradation. Addition of 0.3 mg/L glucose enhanced this removal efficiency to 50.13 +/- 2.51% via co-metabolism. These findings indicated that S. platensis can be used for the removal of CBZ or other PhCs from wastewater. (C) 2019 Published by Elsevier B.V.