Recycling of neomycin fermentation residue using SEA-CBS technology: Growth performance and antibiotic resistance genes

Antibiotic fermentation residue (AFR) is a form of bioavailable matter, that represents a typical category of hazardous waste associated with drug production in China. The disposal of these residues seriously restricts the sustainable development of the pharmaceutical industry. In this study, the steam explosion and aerobic composting (SEA-CBS) system was developed to thoroughly convert neomycin fermentation residue to organic fertilizer. The results implied that the ultimate removal rate of antibiotics was as high as 99.9% in all cases, including macrolide (kitasamycin and spiramycin), lincosamide (lincomycin), and beta-lactam (cephalosporin and penicillin) antibiotic biowastes. Pot experiments were also conducted to study the attenuation rule of antibiotic residues in the soil, and the distribution of antibiotic resistant genes from trace antibiotics. The produced fertilizer presented the better performance on mustard growth than conventional fertilizers. The average plant height and biomass were increased by 14.33%-55.83% and 136.71%-326.83%, respectively, after SEA-CBS pretreatment. Moreover, neomycin was the primary selective pressure, and six antibiotic resistance genes (ARGs) correlated with neomycin were screened. The acc(6')ib gene was identified as the target ARGs, the main resistance mechanism was antibiotic inactivation, and the absolute and relative abundances were 1.06 × 105 ± 3.80 × 104 copies/g and 6.23 × 10-4 ± 1.75 × 10-4 copies/16 s in the NFR-amended soils. The microbial community analysis showed that the variation of the soil microbial community was not dominated by neomycin fermentation residue (NFR) at initial concentrations below 0.42 μg/kg soil. This work demonstrated that the SEA-CBS system not only functioned as an efficient technology for concurrent neomycin sulfate removal and NFR composting, but also applied to a wide range of other antibiotic bio-wastes, which may benefit the recycling of AFR, as well as the data provide a theoretical basis for future agricultural utilization and safe evaluation.