An effective bioremediation approach for enhanced microbial degradation of the veterinary antibiotic sulfamethazine in an agricultural soil

Background The veterinary antibiotic Sulfamethazine (SMZ) contaminates soils via manure applications. Like other soil contaminants (herbicides, fungicides, and nematicides), it has to be degraded. The main challenge is that SMZ biodegradation with bacteria is impeded, since SMZ is a bacteriostatic antibiotic, designed to block microbes in their growth. Results In this study, we enriched the indigenous soil microbial community (including the single strain Microbacterium sp. C448, adapted to SMZ degradation) from a Canadian soil and we present a suitable approach, for soil remediation by inoculating a German soil with this microbial community established on carrier particles, at environmentally relevant concentrations of 1 mg kg −1 . When compared with the isolated SMZ-degrading strain (also obtained from Canada), the microbial community outperformed the mineralization rates of the isolated strain in soil. The negligible soil native SMZ mineralization was successfully increased to 44 and 57 % within 46 days, by the microbial community. The sustainability of this increased SMZ mineralization capacity was proven by the rapid mineralization of a second application of 14 C-SMZ 112 days after the first. Conclusions The pronounced SMZ mineralization and the high amount of non-extractable 14 C-residues (NER) in the inoculated soil indicate that the NER are mainly of biogenic origin (metabolically fixed 14 C). Therefore, the applied inoculation approach decreased the risk of persistent non-extractable SMZ residues. Together with our former studies, this specific soil inoculation approach was tested for three substances with different physico-chemical properties, indicating that this soil bioremediation technique might also be used for other substances. Graphical abstract Biodegradation of sulfamethazine. The veterinary antibiotic sulfamethazine can be excreted by treated animals and introduced to soils via manure application. In our approach we decontaminated soil in a lab experiment with a SMZ degrading strain and the appropriate soil microbial community. With this approach 57 % of the applied SMZ were mineralized within 46 days in soil.