Highly efficient and secure recycling of neomycin fermentation residue by optimum temperature: Nutrients release, neomycin degradation and safety evaluation

The neomycin fermentation residues (NFR) are a solid waste during neomycin production, possessing high recycling value due to their rich organic content. However, the environmentally friendly use of NFR was hindered by its rigid matrix structure and residual neomycin. In this study, the effect of temperature on the structure and bioresource properties of NFR were investigated. Meanwhile, the effect of temperature on the degradation of residual neomycin, the toxicity of neomycin degradation products, and the safety of NFR were assessed. The results indicated that the content of soluble organic matter was increased by appropriate temperature treatment through the disruption of the rigid matrix structure of the NFR. However, excessively high temperatures led to the mineralization of organic matter. Simultaneously, appropriate temperature facilitated the transformation of organic substances to humic-like acids. The neomycin in NFR was effectively degraded with the increasing temperature, and the degradation efficiency exceeded 99 % under 220 °C for 120 min. In addition, the applicability of using appropriate temperatures to degrade antibiotics in similar other AFR has been demonstrated. Neomycin degradation occurred primarily through the cleavage of the glycosidic bond and ring ether, the detachment of the amino group, and the addition of hydroxyl groups. Meanwhile, the developmental toxicity and acute toxicity of neomycin were effectively mitigated by the appropriate temperature, and a significant reduction in ecotoxicity was observed. As a result, optimum temperature treatment proved to be an efficient method for the secure recycling of NFR.