Aerobic biodegradation of acesulfame by sediment-enriched microbial consortia: Kinetics, pathway, and...

Artificial sweetener acesulfame (ACE), an emerging pollutant frequently detected in aquatic environments, exhibits potential ecological toxicity and risk accumulation effects. However, its environmental fate and microbial degradation mechanisms within sedimentary environments remain inadequately characterized. Herein, we established a sediment-based microcosm system to quantitatively characterize the degradation kinetics of ACE, track associated shifts in microbial community structure and function, and decipher the underlying molecular mechanisms. The results showed that successive enrichment cycles significantly augment the aerobic biodegradation of ACE by sediment microbial communities. Under aerobic conditions, the degradation rate constant increased from 0.58 to 3.60 d^-1 following enrichment, significantly exceeding the rate under the anoxic conditions. Metagenomic analysis revealed that ACE treatment reshaped the microbial community structure, with Pseudomonadota remaining the dominant phylum (60.2-65.8%). Genes encoding ACE-degrading sulfatase and amidase were linked to Chelatococcus and Devosia, both of which showed dramatic enrichment in treated samples, underscoring their critical contribution to ACE degradation. A two-step hydrolytic pathway for ACE degradation via sulfonate ester and amide bond hydrolysis was elucidated through combined product analysis. This biodegradation process coincided with significant changes in the abundance of genes governing carbon, nitrogen, and sulfur metabolism, reflecting a functional restructuring of the microbial community. Toxicity assessment indicated that most transformation products exhibited lower toxicity than the parent compound, suggesting an overall reduction in environmental risk. These findings elucidate the microbial degradation mechanisms of ACE, facilitating the assessment of its environmental risks and the development of effective bioremediation strategies.