Effects of different antibiotic operation modes on anaerobic digestion of dairy manure: Focus on microbial population dynamics

Abstract The inhibition effect of four antibiotics, i.e. ampicillin (AMP), tylosin (TYL), florfenicol (FLO) and sulfamethazine (SMT), was investigated in dairy manure digesters for both single dosing and semi-continuous dosing operations over a period of 40 days. High throughput 16 S rRNA sequence analysis revealed that dosing mode did have significant impact on microbial community, i.e. antibiotics had a notable effect on bacteria in single dosing digesters, while archaea were the major population affected in the semi-continuous dosing operations. FLO shows the most severe inhibition on biogas production and remarkably effected bacterial communities, which led to a complete upset of the whole community. Although the effect of SMT on biogas production was marginal, methanogens populations were notably shifted. A four-stage inhibition process on microbial community was proposed based on the ratio of the affected bacteria to archaea to shed new light on microbial population dynamics during anaerobic digestion. Moreover, we found that the semi-continuous operation mode of antibiotics is more efficient in terms of microbial community changes, which may guide the formulation of veterinary drug doses and cycle intervals.