Evaluation of chlorpyrifos tolerance and degradation by no-toxigenic Aspergillus section Flavi strains isolated from agricultural soils

Abstract

This study was conducted to evaluate the in vitro tolerance, utilization and degradation of chlorpyrifos by no-toxigenic Aspergillus section Flavi strains natives of agricultural soils. The tolerance assay showed that all strains were able to grow at the highest insecticide concentration (700 mg L-1). In media supplied with chlorpyrifos, the highest values of growth rate were observed in the full Czapek Dox medium (CZ) (7.2 to 8 mm day-1) and the lowest values were registered in the medium where the insecticide replaced the carbon source (CZC) (3.6 to 4.4 mm day-1). In media where the insecticide replaced the nitrogen (CZN) and phosphorous (CZP) source, the values of growth rate were significantly higher than in CZC and lower than in CZ. Degradation assays showed that the degradation percentage was 75% at 0.98 and 0.95 of water activity, in all concentrations (1753, 3506 and 7012 mg L-1). A fast decrease of chlorpyrifos was observed within the first day of incubation, and then the biodegradation rate decreased over time. This study provides evidence on the effective growth ability and degradation of no-toxigenic Aspergillus section Flavi in presence of high chlorpyrifos concentrations and under optimal growth conditions (aW and temperature).