determination of inhibitory concentration of oxytetracycline on methanogenic bacteria by in vitro study

introduction: 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. methods: 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 inhibitory effect of antibiotic was evaluated by monitoring biogas production. results: based on the findings from each batch, complete inhibitory concentration of oxy tetracycline was in concentration of 800 mg l -1 . significant relation was seen between inoculated antibiotic concentrations and methane production (r=-0.86). conclusion: 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.