Acesulfame degradation within a methane-fed biofilm: a novel and efficient biodegradation route

Acesulfame (ACE), a persistent organic pollutant, is frequently detected across diverse aquatic environments, yet its environmental remediation remains challenging due to the inherently slow biodegradation. Here, we unveil a highly efficient ACE removal strategy using a methane-fed biofilm, achieving a degradation rate of 59.6 mg ACE/g VSS/h. Comprehensive analyses of transformation products (TPs) and toxicity profiles revealed that the biofilm mediated important and effective biodegradation pathways, promoting deep ACE degradation. Microbial community analysis, methane interruption experiments and pure culture studies implicated aerobic methanotrophs Methylococcus sp. and Methylomonas sp. as key players in ACE degradation. Metagenomic and metatranscriptomic analyses demonstrated that these methanotrophs exhibited high expression levels of particulate methane monooxygenase (pMMO) and cytochrome P450 monooxygenase (CYP450) genes within the biofilm community. Enzyme inhibition assays, combined with TP profiling, suggested that pMMO and CYP450 initiated the degradation of ACE. Scavenging experiments further suggested that hydroxyl radicals (•OH) generated through the catalytic activity of pMMO and CYP450 are crucial mediators in the ACE hydroxylation pathway. These findings provide the first evidence of ACE degradation in a methane-fed biofilm system, offering a promising and sustainable approach for the removal of recalcitrant organic contaminants from wastewater.