Hydrothermal treatment of erythromycin fermentation residue: Harmless performance and bioresource properties

Erythromycin fermentation residue (EFR) is a byproduct of bio-fermentation process for producing erythromycin, representing both an economic and environmental burden for the pharmaceutical industry. While hydrothermal treatment (HT) can solve the pollution and toxic problems, the impacts of HT on harmless performance and the bioresource properties of the complex EFR matrix remain unclear. In this study, the abatement of residual erythromycin, its associated antibiotic resistance genes and antimicrobial activity were investigated to evaluate the harmless performance of HT for EFR, and the feasibility of recycling hydrolysates as bioenergy was also assessed. The results showed that raising HT temperature significantly improved the harmless performance. The removal rate of residual erythromycin in EFR reached over 88% and the total absolute abundance of erythromycin resistance genes decreased by more than 3 logs with HT at 160 degrees C for 60 min, but the hydrolysates still existed specific antimicrobial activity against S. aureus.. Additionally, the HT temperature remarkably influenced the bioresource properties of EFR-hydrolyzed products. The release of the protein-like polymers into the liquid phase was enhanced, while high HT temperature worsened the nutrient substances. The elevated drying property of solid products from EFR was observed along with the higher heating value of around 20 MJ/kg, indicating a potential of recycling solid products as biofuel. Total energy production from biogas conversion and biofuel incineration treating 1.0 kg raw EFR was 1875 kJ. Hydrothermal technology was proved to realize the harmless treatment of EFR and meanwhile to be promising for recycling EFR as bioenergy.