Effect of Hydrothermal Pretreatment on Anaerobic Digestion of Erythromycin Fermentation Dregs: Biogas Production, Antibiotic Resistance Gene Evolution, and Microbial Community Dynamics

Abstract

The utilization of erythromycin fermentation dregs (EFD), one kind of solid biowaste, is limited due to the high-level residue of antibiotics. Hydrothermal pretreatment (HT) has great potential to remove residual antibiotics. However, its harmless performance and influence on the EFD anerobic digestion (AD) process remains unclear. In this study, HT was conducted for erythromycin removal before EFD AD with the temperature ranging from 80 to 180°C. Moreover, changes in biogas yield, antibiotic resistance genes (ARGs), and microbial communities in the EFD AD process were compared among different treatments. The results showed that under the optimal hydrothermal temperature of 160°C, more than 85% of erythromycin was eliminated. In addition, HT significantly reduced the ARGs in the EFD AD process and ermT and mefA relative abundance decreased by one order of magnitude. Mobile genetic elements (IntI1 and Tn916/1545) also showed decreased tendency with the hydrothermal temperature elevation. The maximum methane production of 428.3 ml g−1 VS was obtained in the AD system of EFD with hydrothermal treatment at 160°C. It is attributed to the cooperation of hydrolysis and acidogenesis bacteria (e.g., Aminicenantales and Sedimentibacter) and methylotrophic methanogens (Candidatus_Methanofastidiosum and Methanosarcina), and they presented the highest relative abundance in this group. The results indicated that methylated substance reduction was the major methanogenesis route. Hydrothermal technology was of great potential to realize the harmless treatment of EFD and for recycling EFD via AD.