Dissimilarity of different cephalosporins on volatile fatty acids production and antibiotic resistance genes fates during sludge fermentation and underlying mechanisms

The distinct influences of cephalosporins (CEPs, i.e., cefamandole nafate and cefpirome sulfate) affiliated to different generations on the volatile fatty acids (VFAs) production and antibiotic resistance genes (ARGs) fates during waste activated sludge (WAS) fermentation were unveiled. The presence of CEPs mainly exhibited negative effects on the total VFAs production (5%–15% reduction), especially the cefamandole nafate, which is quite different to previous understanding. Further investigation revealed that the CEPs contributed to the solubilization and hydrolysis but inhibited the acidification process by affecting the functional microbial populations (i.e., Tissierella) and general microbial metabolic activities (i.e., pyruvate metabolism and VFAs biosynthesis). In addition, CEPs (especially the cefpirome sulfate) caused the propagation of ARGs (i.e., blaTEM, tetX and mexF) during WAS fermentation. CEPs enhanced the cell membrane permeability to promote the antibiotics mechanism of efflux pump and the horizontal transfer of ARGs. Also, the CEPs altered the regulatory systems (i.e., two component system) and microbial populations associated with ARGs, resulting in the proliferation of specific ARGs. Overall, the dissimilarity of different CEPs impacts on the WAS fermentation for VFAs production and ARGs variations enlightened the diverse environmental behaviors of anthropogenic pollutants and evoked the caution of ecological risks.