Isolation and characterization of cyromazine-degrading bacteria from soil and its application in bioconversion by black soldier fly

Cyromazine, a widely used insect growth regulator, accumulates in livestock manure and poses risks to beneficial insects such as black soldier fly larvae (BSFL) during waste bioconversion. This study isolated two bacterial strains capable of degrading cyromazine, Bacillus subtilis CYR1 (CYR1) and Bacillus velezensis CYR2 (CYR2), from contaminated chicken manure. Both strains demonstrated significant degradation efficiency via hydrolysis of cyromazine to cyanuric acid, a less toxic metabolite. However, in chicken manure systems, degradation efficiency reached a plateau at approximately 20 %, likely due to preferential utilization of alternative nitrogen sources and inherent metabolic constraints. These findings highlight the potential of microbial remediation to mitigate cyromazine contamination while underscoring the need for strain optimization and comprehensive ecotoxicological assessments. The innovative and eco-friendly bioconversion process using black soldier fly larvae is a promising strategy for managing organic solid waste, such as livestock and poultry waste. However, the presence of cyromazine, a common insecticide, poses a significant threat to this process by causing 100 % mortality in larvae even at low concentrations. This graphical abstract highlights the discovery of two bacterial strains, Bacillus subtilis CYR1 and Bacillus velezensis CYR2, which effectively degrade cyromazine and mitigate its harmful effects on the black soldier fly larvae. The study underscores the potential of these bacteria to enhance the bioconversion system's resilience and efficiency, paving the way for large-scale applications in waste management and sustainable agriculture. • Cyromazine-degrading bacteria were isolated from contaminated soil. • Isolated strains efficiently and continuously degrade cyromazine. • Manure pretreatment enhances the growth of black soldier fly larvae (BSFL). • The degradation products and pathway of cyromazine were analyzed.