Algae-mediated bioremediation of ciprofloxacin through a symbiotic microalgae-bacteria consortium

The ciprofloxacin treating via microalga and its microalgae-bacteria consortium was investigated for discussing the potential application of microalgae-mediated bioremediation. As results, the maximum removal efficiency of ciprofloxacin by pure microalgae and the consortium was 87.5 +/- 3.5 % (5 mg/L) and 96.1 +/- 0.07 % (40 mg/L), respectively. The consortium enhanced the degradation rate to 0.81 d-1 compared with the pure microalgae (0.27 d-1). To reveal the symbiotic mechanism, extracellular polymeric substances, pigments contents, antiox-idant enzymes and symbiotic bacterial community were analyzed. The malondialdehyde content in the pure microalgae (1622.6 +/- 38.7 nmol/mg protein) was higher than that in the consortium (298.34 +/- 2.4 nmol/mg protein), and there were obvious chlorophyll b accumulations (approximately 90 %) in consortium. In addition, the symbiotic bacteria had a positive effect on microalgal secretion of fulvic acid-type components. As mecha-nism, symbiotic bacteria improved ciprofloxacin biodegradation by reducing cell damage and secreting fulvic acid. The presence of Phycisphaeraceae and Rhizobiaceae, nitrogen fixation bacteria, in the consortium suggest that improvement of ciprofloxacin biodegradation might be associated with nitrogen co-metabolism as well. Collectively, this work elucidates the mechanism of enhancing elimination of ciprofloxacin via microalgae-bacteria consortium and accelerates development of microalgae-mediated aquaculture tailwater bioremediation.