Isolamento, seleção e avaliação do potencial de biodegradação de glifosato (n-(Fosfonometil)glicina) por microrganismos isolados de solo de lavoura, em Laranjeiras do Sul, PR.

Abstract

The abusive use of glyphosate, one of the most widely used pesticides in Brazil is related to health issues and the environment. Therefore, this study aimed to isolate, evaluate the growth capacity or degradation and subsequently identify indigenous microorganisms degrading glyphosate in a soil with intensive use of this pesticide. The 12 samples were collected randomly soil (0-10 cm depth), homogenized and them 1 g of the sample was transferred in a flask containing 50 ml of mineral medium (MM) (g/L KCl 0.7; KH2PO4 2.0; Na2HPO4, 3.0; NH4NO3 1.0; MgSO4 1.0; FeSO4 4.0; MnCl2, 0.2; CaCl2 0.2; pH 7.2) with 100 mg/L glyphosate (as sole carbon source) 3 subsequent transfers (1 ml) every five days and incubation at 28 ° C. Bacteria and fungi morphologically different were isolated on nutrient agar, and Sabouraud with 300 mg/L of glyphosate, respectively. The following fungi were incubated on solid MM agar with 300 mg/l glyphosate as sole carbon source at 28 ° C by 14 days. The radial mycelial growth was daily measured and the growth rate were calculated by linear regression using the colonies rays. Of the total of 18 fungal isolates, 11 used glyphosate as a carbon source. eight genera of filamentous fungi and two false fungi, with the highest rates of radial growth were identified. The genres that stood out were: Aspergillus, Fusarium sp, Penicillium sp... and Geotrichum sp. 25 Bacteria were isolated (47% gram-negative bacilli), these six remained viable by the experiment of glyphosate degradation. To prepare the inoculum, was transferred to a Erlenmeyer flasks with 100 ml of nutrient broth and 300 mg/L of glyphosate, incubated at 150 rpm by 48 h. After three washes (MM), the inoculum was standardized using McFarland scale. The potential for degradation of the test isolates was performed with incubation inoculum (5x106 CFU/ml) in MM in the absence or presence of different concentrations of glyphosate (300, 500 and 700 mg/L) using redox indicator 2,6-dichlorophenol-indophenol (DCPIP), incubated in a greenhouse (28 °C) and spectrometric measured at 600 nm in 0-120h period. The 6 bacterial strains tested showed DCPIP degradation rate at the concentrations tested, indicating that possibly used glyphosate as a carbon source. The B8 bacteria in relation to the others, was the most reduced the amount of DPCIP. The results suggest that microorganisms are tolerant and have a high potential for glyphosate degradation and can be used in future studies of bioremediation of soils contaminated with this pesticide.