Influence of zinc on biogas production and antibiotic resistance gene profiles during anaerobic digestion of swine manure

This study determined the accumulated biogas, methane content, and absolute abundances (AAs) of 14 common antibiotic resistance genes (ARGs) and two integrons during the anaerobic digestion of swine manure for 52 days with different amounts of added zinc. The accumulated biogas increased by 51.2% and 56.0% with 125 mg L-1 (L) and 1250 mg L-1 (H) zinc, respectively, compared with the control with no added zinc (CK), but there was no significant difference between L and H. Compared with CK, excluding tetW and tetC, all the other ARGs detected in this study increased in the L and H reactors. However, the low concentration of zinc (L reactor) caused greater increases in the AAs of ARGs in the AD products. Redundancy analysis showed that NO3-N and bio-zinc significantly explained the changes in genes, where they accounted for 60.9% and 20.3% of the total variation in the environmental factors, respectively.