Safe utilization of bioresources in gentamicin mycelial residues by thermal treatment: Antibiotic degradation, resistance gene inactivation and available nutrients promotion

Gentamicin mycelium residues (GMRs) abundant in organic substances were generated during the production of gentamicin. Inappropriate handling techniques not only waste valuable resources, they could also result in residual gentamicin into the natural environment, leading to the generation of antibiotic resistance genes (ARGs), which would cause a significant threat to ecological system and human health. In the present work, the effects of thermal treatment on the removal of residual gentamicin in GMRs, as well as the changes of associated ARGs abundance, antimicrobial activity and bioresources properties were investigated. The results indicated that the hazards of GMRs was significantly reduced through thermal treatment. The degradation rate of residual gentamicin in GMRs reached 100 %, the total abundance of gentamicin resistance genes declined from 8.20 to 1.14 x 10(-5) and the antibacterial activity of the decomposition products of GMRs on Vibrio fischeri was markedly reduced at 200 C-degrees for 120 min. Additionally, the thermal treatment remarkably influenced the bioresource properties of GMRs-decomposition products. The release of soluble organic matters including soluble carbohydrates and soluble proteins have been enhanced in GMRs, while excessively high temperatures could lead to a reduction of nutrient substances. Generally, thermal treatment technology was a promising strategy for synergistic reducing hazards and utilizing bioresources of GMRs.