Bioremediation of metribuzin-contaminated soil by corn straw biochar-immobilized Bacillus cereus N1

The bioremediation effects of metribuzin-degrading bacterium Bacillus cereus N1 immobilized with corn straw biochar (BC) were studied. The results showed that 72.15% of strain N1 and 15.31% of metribuzin was adsorbed by BC, with the highest absorption peak intensity obtained by the immobilized bacterial microspheres (PSBN1). The Mechanism of PSBN1 removal of metribuzin was investigated using scanning electron microscopy, distribution and mass transfer pathways of metribuzin in PSBN1, and adsorption kinetics and isotherms of BC. A total of 62.26% of metribuzin was degraded by PSBN1 in 120 d of storage at 4 °C, which could be reused for 7 times with the degradation efficiency maintained above 75%. The optimal degradation conditions of metribuzin were determined to obtain the degradation rate of 92.48% in 5 d. The degradation rates of metribuzin reached 84.12% and 83.73% in sterilized and non-sterilized soils, respectively, in 28 d. The bioremediation effect of PSBN1 was verified by the maximum recovery rate (183%) of fresh plant weight in metribuzin sensitive crop and the greatly restored soil enzymatic activities. To conclude, PSBN1 was suitable for extended storage time with high degradation efficiency maintained, providing strong experimental evidence to support the commercialization and long-term preservation of metribuzin-degrading microbial agents.