Transformation of Roxarsone by bacterial consortium Isolated from soil in aerobic condition

Roxarsone (ROX), an organoarsenical compound used as food additive in the poultry industry, has the potential risk to contaminate the environment, mainly by the use of poultry industry manure as fertilizer. The aim of this work was to isolate and characterize a bacterial consortium from agricultural soil, capable of degrading ROX under aerobic conditions. Soil samples were collected from a poultry industry (Bio Bio Region, Chile) and were enriched in 9.1% (weight/volume) R2A broth at room temperature. The selected bacterial consortium was grown in the absence and presence of 0.5 mM ROX at 25 C with agitation (125 rpm) and under aerobic conditions. The consortium was characterized by DGGE coupled to a multidimensional scaling analysis (MD S). Shannon-Weaver (H') and Pielou (J') indexes were determined. In addition, effects of abiotic factors (temperature and pH) and carbon sources on the transformation of ROX were evaluated in a chemically defined medium (CDM). The results showed that the growth rate was 1.38-fold higher in ROX presence and that ROX degradation was 41.6% after 168 h of incubation. MDS results demonstrated that the consortium structure changes from 70% to 50% similarity while a decrease and increase in indexes of H' and J', respectively, was observed in the presence of ROX. Abiotic factors assessment showed that after 120 h incubation, at 37 degrees C and pH 7, when using lactate as carbon source ROX reduction reached 57.8% but when glucose was used ROX biotransformation reached 62.3%, exceeding other carbon sources used. Microbiological degradation of ROX under aerobic conditions has been rarely reported and it has a potential environmental impact on agricultural soils fertilized with ROX contaminated manure.