Removal of ciprofloxacin from aqueous media by Chlorella pyrenoidosa, Scenedesmus obliquus, and isolated Stichococcus bacillaris: A comparative study on toxicity, removal mechanism and biochemical composition

This study investigates the acute toxicity and removal capacity of the native isolated species Stichococcus bacillaris towards Ciprofloxacin (CIP) and compared its efficiency with the most explored algal species Chlorella pyrenoidosa and Scenedesmus obliquus in antibiotic removal. The toxicity assessment revealed that 24 hr EC50 values are in the order of Stichococcus bacillaris (64 mg/L) > Chlorella pyrenoidosa (52 mg/L) > Scenedesmus obliquus (42 mg/L) and 24 hr LC50 values are in the order of Stichococcus bacillaris (313 mg/L) > Chlorella pyrenoidosa (228 mg/L) > Scenedesmus obliquus (197 mg/L). Furthermore, CIP (5 mg/L) was spiked into the algal medium to study their removal potential for 7 days. Stichococcus bacillaris and Scenedesmus obliquus reported higher removal efficiency (40%) compared to Chlorella pyrenoidosa (28%) with biodegradation as the major contributing removal mechanism in all the species with the order of Stichococcus bacillaris (84%) > Scenedesmus obliquus (80%) > Chlorella pyrenoidosa (59%). Biochemical characterization revealed that Scenedesmus obliquus is a suitable candidate for biodiesel production as the lipid production (830 mg/L) is higher in this species and Stichococcus bacillaris is suitable for bioethanol production as the carbohydrates production (609 mg/L) is substantial in this species.