Effects of sulfamethoxazole on the microbial community dynamic during the anaerobic digestion process

The practice of fertilizing soils with livestock manure, containing veterinary antibiotic residues, is known to spread antibiotic resistance in agricultural soil. In contrast, the fate of antibiotic residues in anaerobic digesters fed with manure is still poorly understood. For example, it is not clear if the biocide action of the antibiotic prevails by reducing the activity of the microbial community responsible for the anaerobic digestion process or if the overall microbial community is able to degrade antibiotics. This work aims to improve knowledge on these questions, evaluating if the energetic valorisation of manure through anaerobic digestion can be a treatment able to reduce the concentration of antibiotics in the resulting digestate, commonly used as fertilizer to replace chemical ones. Sulfamethoxazole (SMX) is one of the most detected antibiotics in agricultural ecosystems and its presence in cattle-manure can affect the anaerobic digestion process. New data about the effects of SMX on the anaerobic digestion process in terms of both biogas production (CH4 and H2) and shifts in the microbial community involved are presented. Moreover, the effect of SMX addition on the selection of ARG harboring bacteria are also evaluated and discussed.