Biodegradation of triazine herbicide metribuzin by the strain Bacillus sp. N1

Abstract

By enrichment culturing of soil contaminated with metribuzin, a highly efficient metribuzin degrading bacterium, Bacillus sp. N1, was isolated. This strain grows using metribuzin at 5.0% (v/v) as the sole nitrogen source in a liquid medium. Optimal metribuzin degradation occurred at a temperature of 30ºC and at pH 7.0. With an initial concentration of 20 mg L⁻¹, the degradation rate was 73.5% in 120 h. If the initial concentrations were higher than 50 mg L⁻¹, the biodegradation rates decreased as the metribuzin concentrations increased. When the concentration was 100 mg L⁻¹, the degradation rate was only 45%. Degradation followed the pesticide degradation kinetic equation at initial concentrations between 5 mg L⁻¹ and 50 mg L⁻¹. When the metribuzin contaminated soil was mixed with strain N1 (with the concentration of metribuzin being 20 mg L⁻¹ and the inoculation rate of 10¹¹ g⁻¹ dry soil), the degradation rate of the metribuzin was 66.4% in 30 days, while the degradation rate of metribuzin was only 19.4% in the control soil without the strain N1. These results indicate that the strain N1 can significantly increase the degradation rate of metribuzin in contaminated soil.

Keywords:

• Metribuzin
• triazine herbicide
• biodegradation
• Bacillus sp. N1
• GC
• phylogenetic analysis

Acknowledgments

Hao Zhang and Yubin Zhang contributed equally to this work and are co-first authors. This study is supported by grants from the National Science and Technology Pillar Program during the Twelfth Five-Year Plan Period (2012 BAD19B04 to H. Pan), the Jilin Science and Technology Development Plan (20120742 to H. Zhang), the Ministry of Agriculture Public Benefit Industry of the P. R. China (20113016 to H. Pan), and the World Bank Jilin Agricultural Product Quality and Safety Project (2011-Z28). We thank Dr. Steven Clough at the USDA and the Department of Crop Sciences at the University of Illinois at Urbana-Champaign for helping us edit English of our manuscript.