Determination of Inhibitory Concentration of Oxytetracycline on Methanogenic Bacteria by in Vitro Study

Antibiotics have the potential to adversely affect the microbial community. For anaerobic digestion, a sufficient methanogenic population needs to be preserved in the system.The main aim of this study was determination of inhibitory concentration of oxytetracycline on methanogenic bacteria. A 120 mL jacketed bioreactor with a 90 mL working volume was inoculated granular sludge from an anaerobic digester, substrate and different concentration of oxytetracycline with 10 days cycles and intermittent mixing. The reactor was operated at 35 ± 2 ° C. The inhibitoryeffect of antibiotic was evaluated by monitoring biogas production. Based on the findings from each batch, complete inhibitory concentration of oxytetracycline was in concentration of 800 mg L-1.Significant relation was seen between inoculated antibiotic concentrations and methane production (r=-0.86). The addition of antibiotics to the biomass affected the utilization of fatty acids, resulting in unfavorable effects on methanogenesis. Thus, overusing of antibiotics can adverse effects of intestinal flora.