Biodegradation of the fungicide Pyraclostrobin by bacteria from orange cultivation plots.

ABSTRACT

The pesticides belonging the strobilurin group are among the most common contaminants in the environment. In this work, biodegradation studies of the strobilurin fungicide Pyraclostrobin by bacteria from orange cultivation plots were performed aiming to contribute with the development of a bioremediation method. Experiments were performed in triplicate with validated methods, and optimization was performed by Central Composite Design and Response Surface Methodology. The strains were evaluated in liquid nutrient medium containing 100 mg L-1 of Pyraclostrobin, and decreased concentrations of 61.5 to 100.5 mg L-1 were determined after 5 days at 37 °C and 130 rpm, showing the importance of strain selection. When the five most efficient strains (Bacillus sp. CSA-13, Paenibacillus alvei CBMAI2221, Bacillus sp. CBMAI2222, Bacillus safensis CBMAI2220 and Bacillus aryabhattai CBMAI2223) were used in consortia, synergistic and antagonistic effects were observed accordingly to the employed combination of bacteria, resulting in 64.2 ± 3.9 to 95.4 ± 4.9 mg L-1 residual Pyraclostrobin. In addition, the formation of 1-(4-chlorophenyl)-1H-pyrazol-3-ol was quantified (0.59-0.01 mg L-1), and a new biodegradation pathway was proposed with 15 identified metabolites. Experiments were also performed in soil under controlled conditions (30 °C, 0-28 days, 100 mg kg-1 pesticide), and the native microbiome reduced the pesticide concentration to 70.4 ± 2.3 mg L-1, whereas the inoculation of an efficient bacterial consortium promoted clearly better results, 57.2 ± 3.9 mg L-1 residual Pyraclostrobin. This suggests that the introduction of these strains in soil in a bioaugmentation process increases decontamination. However, the native microbiome is important for a more efficient bioremediation.