Hydrothermal treatment enhances the removal of antibiotic resistance genes, dewatering, and biogas production in antibiotic fermentation residues.

Antibiotics and antibiotic resistance genes (ARGs) are enriched in antibiotic fermentation residues (AFRs). In this study, we investigated the effect of hydrothermal treatment on dewatering, biogas production, and removal of ARGs in the penicillin fermentation residue (PFR). Solid, 120 µm particles in the PFR were disintegrated to 30 - 40 µm after 140 - 180 °C hydrothermal range. Of extracellular polymeric substance, 79.8 ± 0.4% was decomposed to release 82.2 ± 0.6% of bound water at 180 °C. The effective solid-liquid separation was achieved only after a hydrothermal treatment of 180 °C. More than 75% of organic matter in the filtrate was transformed into biogas by the upflow anaerobic sludge blanket (UASB). The absolute abundance of 16 S rRNA and ARGs decreased by 2.4 - 5.2 logs after hydrothermal treatment. The ratio of extracellular ARGs (eARGs) to total ARGs increased at 80 °C and decreased at higher temperature (>120 °C). The absolute abundance of ARGs increased by 0.7 - 1.6 logs in anaerobic digestion, and the relative abundances of ARGs based on 16 S rRNA plummeted by 3 logs. Most (98.7 ± 0.4%) ARGs were distributed in suspended solids and were removed by membrane filtration. Hydrothermal treatment demonstrated broad applicability to 10 varieties of AFRs.

Combined hydrothermal treatment, pyrolysis, and anaerobic digestion for removal of antibiotic resistance genes and energy recovery from antibiotic fermentation residues.

A process combining hydrothermal treatment (HT), pyrolysis, and anaerobic digestion can efficiently treat antibiotic fermentation residues (AFR). The process characteristics and antibiotic resistance genes (ARGs) removal efficiencies of each unit have been investigated. HT of 180 °C improved the biodegradability and dewaterability of the AFR. Pyrolysis of 500 °C and upflow anaerobic sludge blanket (UASB) of 6.5 ± 0.5 kg COD•(m3•d)-1 recovered the organic matter in filter cake and filtrate of AFR. The biogas and pyrolysis gas can compensate the energy this system needs. HT of 180 °C could reduce 16S rRNA, ARGs, and mobile genetic elements (MGEs) by 2.3 to 7.4 logs. UASB increased the copy numbers of ARGs and MGEs, but the relative abundances of ARGs normalized against 16S rRNA were significantly declined. The ARGs and MGEs were enriched in suspended solids of digestate. The application of this process can promote the resources recycling of fermentation waste.