Tylosin in anaerobic reactors : degradation kinetics, efects on methane production and on the microbial community.

Abstract

Tylosin eliminated in animal waste, during therapeutic treatment, can be efciently removed in anaerobic systems. The present study investigated the infuence of tylosin concentration and assessed its degradation kinetics and the microorganisms involved in each stage of its anaerobic digestion (hydrolysis/ acidogenesis; acetogenesis; methanogenesis). The results showed a stimulating efect on methane production with increasing tylosin concentration in the poultry litter up to 80 mg kg−1 tylosin (232.9 NL CH4 kg SV−1). As for tylosin degradation, greater removal of antibiotics was observed in the methanogenic phase (88%), followed by acetogenic (84%) and hydrolytic/acidogenic (76%) phases. The higher rate of tylosin degradation obtained in the methanogenic step, is mainly related to the co-metabolic efect exerted by the presence of acetate and its degradation by acetoclastic methanogens. Indeed, metagenomic analyses suggested a syntrophic action between archaea of the genus Methanobacterium, and bacteria such as Clostridium and Flexilinea, which seemed decisive for tylosin degradation.