In-situ remediation efficiency and mechanism of tylosin contaminated soil with biochar immobilized degrading enzyme.

Residues of veterinary antibiotics such as tylosin in soils can induce selective pressure on indigenous soil microbes and increase the dissemination risk of antibiotic resistance genes (ARGs) by horizontal gene transfer (HGT), which poses a serious threat to both soil and public health. While conventional bioremediation methods face challenges in efficiency and stability, enzyme-based approaches offer promising alternatives. This study developed a novel biochar-immobilized tylosin-degrading enzyme (BIE) system to simultaneously address tylosin contamination and antibiotic resistance gene (ARG) proliferation in agricultural soils. Using HPLC-MS, qPCR, and 16S rRNA sequencing, we comprehensively evaluated tylosin degradation kinetics, ARG dynamics, and microbial community responses during BIE treatment towards tylosin-contaminated soil. The results revealed the remarkable degradation efficiency of tylosin (99.85 %) by BIE within 7 days. In addition, after 20 days of BIE treatment, the relative abundances of ARGs and mobile gene elements (MGEs) significantly decreased by 11.63-100 % depending on the specific gene which favored the recovery of soil bacterial community diversity. Mechanistic studies revealed that biochar synergistically enhanced enzyme stability and provided protective microenvironments, enabling efficient lactone bond hydrolysis and tylosin detoxification. These findings establish biochar-immobilized degrading enzyme technology as a sustainable solution for dual challenges of antibiotic persistence and resistance spread in contaminated soils. Future research should focus on field validation, large-scale application protocols, and long-term ecological impacts to facilitate practical implementation of this innovative approach.