Key microbial clusters and environmental factors affecting the removal of antibiotics in an engineered anaerobic digestion system

anaerobic digestion (AD) systems, the dynamic characteristics of antibiotics, physiochemical factors, microbial communities and functional genes were investigated by 16S rRNA and metagenome sequencing. The results showed that antibiotic removal occurred mainly in the first 21 days, and sulfonamides had the highest removal rate. The key microbial clusters related to the biodegradation of antibiotics consisted mainly of Firmicutes and Bacteroidetes. The key enzymes consisted of deaminases, peptidases, C-N ligases, decarboxylases and alkyl-aryl transferases. Structural equation modelling indicated that low concentrations of propionic acid promoted the biodegradation activities of key microbial clusters in the first 21 days, but their activities were inhibited by the accumulated propionic acid after 21 days. Thus, propionic acid should be regulated in engineered AD systems to prevent the adverse effect of acid inhibition on antibiotic-degrading bacteria.

Automated summary

This study investigated the dynamic characteristics of antibiotics in anaerobic digestion (AD) systems, including physiochemical factors, microbial communities, and functional genes. The results revealed that antibiotic removal mainly occurred in the first 21 days, with sulfonamides having the highest removal rate. Key microorganisms involved in antibiotic biodegradation belonged to Firmicutes and Bacteroidetes. Key enzymes involved in the process included deaminases, peptidases, C-N ligases, decarboxylases, and alkyl-aryl transferases. Structural equation modeling showed that low concentrations of propionic acid promoted microbial activity during the first 21 days, but its accumulation inhibited activity afterwards. Therefore, regulating propionic acid in engineered AD systems is important to prevent the adverse effect of acid inhibition on antibiotic-degrading bacteria.