Acesulfame Anoxic Biodegradation Coupled to Nitrate Reduction by Enriched Consortia and Isolated Shinella spp

Acesulfame (ACE) is considered to be an emerging pollutant associated with growing concerns. Although aerobic biodegradation of ACE has been observed in wastewater treatment plants worldwide and verified in pure cultures, limited information is available on ACE biodegradation under anoxic conditions, which are ubiquitous in natural environments. Here, we found that ACE could be mineralized completely via a process coupled with nitrate reduction by enriched consortia, with the highest degradation rate of 9.95 mg ACE/g VSS·h^-1. Meanwhile, three novel ACE-degrading strains affiliated with Shinella were isolated, examined, and sequenced, revealing that the isolates could utilize ACE as the sole carbon source under both aerobic and anoxic conditions, with maximum degradation rates of 30.3 mg ACE/g VSS·h^-1 and 8.92 mg ACE/g VSS·h^-1, respectively. Additionally, the biodegradation of ACE was suspected to be a plasmid-mediated process based on comparative genomic analysis. In ACE-degrading consortia, 83 near-complete metagenome-assembled genomes (MAGs) were obtained via Illumina and Nanopore sequencing, showing that Proteobacteria and Bacteroidetes were the dominant phyla. Moreover, nine MAGs affiliated with Hyphomicrobiales were proposed to be the major ACE degraders in the enrichments. This study demonstrated that ACE could be degraded under anoxic conditions, providing novel insights into ACE biodegradation in the environment.