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.