Effects of enrofloxacin and sulfamethoxazole on Haematococcus lacustris

In this study, we investigated the pigments, biochemical composition, and oxidative stress responses in control cultures of Haematococcus lacustris and in cultures supplemented with varying concentrations (0.1, 1, 10, 100, and 1,000 mg/L) each of enrofloxacin (ENR) and sulfamethoxazole (SMX) throughout the life cycle of H. lacustris. Among ENR-supplemented cultures, the highest levels of chlorophyll (chl) a, chl b, and total carotenoids were observed in the culture treated with ENR-100 mg/L on day 9. For SMX-supplemented cultures, the SMX (1 mg/L)-treated culture had the highest chl a and chl b on day 9, while the SMX (10 mg/L)-supplemented culture had higher astaxanthin and total carotenoids than the control on day 9. On day 15, the cultures treated with each of SMX-100 mg/L and ENR-1,000 mg/L achieved the highest biomass dry weight and yielded the highest cell density. At the same time point, culture supplemented with ENR-1,000 mg/L demonstrated the highest levels of total protein. The cultures supplemented with each of ENR-1 mg/L and SMX-1 mg/L exhibited the highest total carbohydrate content on day 15. Superoxide dismutase activity was higher than the control for the SMX-1 mg/L treated culture on day 12 and for the SMX-10 mg/L treated culture on days 9, 12, and 15, while malondialdehyde levels were higher than the control for the ENR-1 mg/L treated culture on day 6 and for the ENR-(0.1, 10, and 100 mg/L) and SMX-1 mg/L treated cultures on day 9. The EC50 values for ENR and SMX on H. lacustris were 16.91 mg/L and 20.19 mg/L, respectively. Supplementation of low doses of antibiotics increased the pigment levels in H. lacustris, while higher doses boosted the cell growth and biomass DW.