Ampicillin biotransformation by a nitrifying consortium.

ABSTRACT

Ampicillin is a widely used ß-lactam antibiotic that has been detected in various effluents and can alter biological processes used in wastewater treatment such as nitrification. Physiological and kinetic behaviour of a nitrifying consortium in the presence of ampicillin (AMP) (10, 25, and 50 mg/L) was evaluated in batch cultures. Under the experimental conditions (320 ± 8 mg bacterial protein/L, C/N = 2.4, 24 h), the nitrifying behaviour was very similar among the controls without AMP and the assays with antibiotic, as there was no AMP effect on efficiency (ENH4+ = 99.7 ± 4.2%), yields (YNO2- = 0, YNO3- = 1.0 ± 0.1 mg N/mg NH4+-N consumed), neither specific rates of NH4+ oxidation and NO3- formation. Therefore, nitrifying bacteria were insensitive to AMP presence. At all assayed concentrations, after 24 h, 70.5 ± 3.7% of AMP was removed from the cultures through abiotic (16.0-16.5%), biosorption (23.2-47.0%), and biotransformation (10.0-29.8%) processes. With the increase in the initial AMP concentration, a greater participation of the biotransformation process, associated to an increase in the specific AMP consumption rate was attained. The sludge was able to completely oxidize NH4+ to NO3- by nitrification and eliminate AMP biologically, but without reaching its full mineralization.