Changes and distributions of antibiotic resistance genes in liquid and solid fractions in mesophilic and thermophilic anaerobic digestion of dairy manure

This study mainly explored the changes and distributions of antibiotic resistance genes (ARGs) in liquid fraction (L-F) and solid fraction (S-F) in anaerobic digestion (AD) of dairy manure. After mesophilic and thermophilic AD, the copy numbers of ARGs in L-F decreased by 0.06-1.80 logs while those in S-F increased by 0.08-7.85 logs, suggesting the enrichment of ARGs in S-F. Statistical analysis elucidated that high total solids promoted the enrichment of ARGs in S-F. The increased abundances of genera such as Ruminofilibacter, Treponema and Sphaerochaeta in S-F were responsible for the enrichment of most ARGs. These insights demonstrated the digested solid had the potential risks to promote the spread of ARGs in the environment, and the digested solid of livestock manure should be post-treated before the application.

Automated summary

The study explored changes and distributions of antibiotic resistance genes (ARGs) in the liquid and solid fractions during anaerobic digestion of dairy manure. It found that ARGs were enriched in the solid fraction after digestion, with high total solids promoting their enrichment. Increased abundances of certain bacterial genera were responsible for the enrichment of most ARGs in the solid fraction.