1H-1,2,4-Triazole biodegradation by newly isolated Raoultella sp.: A novel biodegradation pathway

In this study, a novel 1H-1,2,4-triazole (TZ) degrading strain was isolated from activated sludge acclimated by TZ and was identified as Raoultella sp. The biodegradation test showed that Raoultella sp. could utilize TZ as the sole carbon and nitrogen source. TZ was completely removed at incubation temperature of 30 °C, initial pH of 7.0 and initial concentration of 100 mg L−1 within 288 h, which was accompanied by obvious TOC removal, NH4+ release, pH increase, biomass growth, biotoxicity reduction and excitation emission matrix (EEM) variation. TZ biodegradation profile by Raoultella sp. was well fitted by the first-order degradation kinetic model, confirming the inhibitory nature of TZ. Based on HPLC/MS analysis, a distinct TZ biodegradation pathway including hydroxylation, carbonylation, carboxylation and ring cleavage, was proposed for the first time. Compared with other TZ degrading species such as Shinella sp., Raoultella sp. showed relatively higher TZ removal efficiency, demonstrating great potential for the application in biological treatment of wastewater containing TZ in practice.