Anaerobic biodegradation of pharmaceutical compounds: New insights into the pharmaceutical-degrading bacteria

Antibiotics and hormones are among the most concerning trace contaminants in the environment. Therefore, the present work aimed to identify anaerobic microorganisms with the ability to remove pharmaceutical products (PhPs) belonging to these two classes (ciprofloxacin, 17β-estradiol and sulfamethoxazole) under different anaerobic conditions, and to elucidate the bio-removal mechanisms involved. Ciprofloxacin was efficiently biodegraded under both nitrate- and sulfate-reducing conditions reaching a PhP removal superior to 80%, whereas 17β-estradiol was only biodegraded under nitrate-reducing conditions reaching a removal of 84%. No biodegradation of sulfamethoxazole was observed. In nitrate-reducing conditions the ciprofloxacin-degrading community was composed of Comamonas, Arcobacter, Dysgonomonas, Macellibacteroides and Actinomyces, genera while Comamonas and Castellaniella were the main bacteria present in the 17β-estradiol-degrading community. In sulfate-reducing conditions the community was mainly composed by bacteria affiliated to Desulfovibrio, Enterococcus and Peptostreeptococcus. Interestingly, the PhP under study were biodegraded even in the absence of additional carbon source, with 85% of ciprofloxacin removed under sulfate-reducing conditions and 62% and 83% of ciprofloxacin and estradiol removed, respectively, under nitrate-reducing conditions. This work provides new insights into anaerobic bioremediation of PhP and novel PhP-degrading bacteria.