Metagenomic analysis elucidates the dose-dependent impact of ofloxacin on sludge anaerobic fermentation for short-chain fatty acid production

Antibiotics significantly impact the anaerobic fermentation of waste activated sludge (WAS). However, only a few studies have been conducted on the influence of ofloxacin (OFL) on the production of short-chain fatty acids (SCFAs) and its underlying mechanisms during WAS anaerobic fermentation. This study aimed to elucidate the impact of OFL on SCFA production from alkaline-pretreated WAS fermentation. The results showed that the addition of 10 mg OFL/kg SS led to a peak concentration of 2931.85 mg COD/L, resulting in a 1.1-fold increase in SCFA production compared to the control group. Further exploration revealed that OFL simultaneously promoted WAS solubilization, hydrolysis and acidification. Additionally, a low concentration of OFL increased the abundance of hydrolytic acidifying bacteria but decreased the abundance of SCFA-consuming bacteria. Metagenomic analysis revealed an enhanced abundance (103.76–134.56%) of critical genes related to extracellular hydrolysis (i.e., malZ , bglX , and degP ), membrane transport (i.e., msmX , gtsA , and gltI ), substrate metabolism (i.e., glk , glnA , and gdhA ), and SCFAs biosynthesis (i.e., ackA and fabG ) in the presence of low OFL concentration. These findings broadened our understanding regarding the influence exerted by OFL on WAS anaerobic fermentation.