Seleção de bactérias resistentes a Fe3+ com potencial aplicação em biorremediação

Abstract

Bioremediation is a technique which uses the metabolism of microorganisms in the treatment of areas impacted with organic or inorganic toxic compounds, such as trace elements. The use of bacteria as agents in bioremediation processes of soil contaminated with trace elements, such as iron, manganese among others, is a promising alternative for recovering these environments. The objective of this work was to select bacteria isolated from preserved soils in the Cerrado region and of coffee and cocoa fruits capable of growing in different concentrations of Fe3+. The isolates belong to the Culture Collection of the Microorganism Physiology and Genetic Laboratory of the Biology Department of UFLA. The evaluation of growth capacity at high concentrations of iron was performed using the Chemically Defined (CD) medium, containing iron solution concentrations of 5, 500 and 1000 mg/L and the control with no addition of iron. The UFLACESB 127 (Bacillus simplex) bacteria of the Cerrado soil, UFLASCF 590 (Bacillus subtilis) coffee bacteria and UFLADR 6.12 (Acetobacter tropicalis) cocoa bacteria isolated were highlighted for presenting better growth when cultivated in CD with the maximum concentration of iron. The selection of the physical factors was performed using the Plackett-Burman (PB) type experimental planning, followed by a central rotatable composite design (CRCD). The studied variables were: pH, glucose concentration, iron concentration, inoculum concentration, nitrogen concentration, potassium concentration, phosphate concentration and ecoenzyme, with the response variable analyzed being iron absorption in 7 days of cultivating and the interpretation of the results done with the Design-Expert 8.0 program. Among the variables tested in the PB, those which presented significant results were pH 3.5 and iron concentration of 0.750 g/L, with these conditions optimized by the statistical program for the iron absorption process of the selected bacteria. After the optimization stage we obtained the efficiency of 99.22%, with validation performed in order to confirm the model for the experimental results. These results indicate that there is potential for the use of these isolates in removing iron when the conditions are adjusted, and may be a promising alternative to the conventional treatment methods of contaminated soils. However, it is necessary to understand the mechanisms and the capacity of iron removal of these isolated in different types of soil.