Biodegradação de hidrocarbonetos por rizobactérias em solo de várzea da Região Amazônica contaminado com petróleo e óleo diesel

Abstract

Due to the great environmental impact caused by accidents involving petroleum activities and the difficulty of its treatment, bioremediation processes have been widely studied and, with this, microorganisms capable of degrading oil are increasingly used. This work evaluated the biodegradation potential of five rhizobacteria, identified as INPA R560 (Bradyrhizobim sp), R631 (Bradyrhizobim sp), R557 (Bradyrhizobim sp), R677 (Rhizobium sp) and R674 (Alicyclobacillus sp) and the mixture of them in samples of floodplain soil contaminated with 1% diesel oil and petroleum. For this purpose, an experiment was carried out using microbial suspension of each rhizobacterium and the consortium with the five bacteria in 500 g of autoclaved soil and diesel oil in one experiment and oil in another experiment as a carbon source. Two control samples were also used for each experiment, one containing sterile soil and the other non-sterile, using the same conditions as the samples, without the addition of microorganisms. To evaluate the degradation potential of aromatic and aliphatic hydrocarbons, collections were carried out at zero times, 48 hours and after the 21-day period in the experiment with diesel oil. In the oil experiment, evaluations were made at the same times, but with an additional evaluation in the period of 10 days. Among the five rhizobacteria evaluated, with the exception of the INPA R631 isolate, the removal values of n-alkanes by the other tested isolates were above 80% after the 21-day period. The consortia, with the mixture of the five species, also showed considerable removal rates of n-alkanes with a value of 67.57% in the experiment with diesel oil and 67.80% in the experiment with oil. Regarding PAH, the bacteria showed a high potential for degradation in the first 48 hours, especially the species INPA R557, INPA 677 and a consortium with the five isolates with degradation rates of 71.57%, 38.18% and 41.84 %, respectively. Of the tested isolates, two showed a total HPA degradation rate of 85.85% and 75.53% after the 21-day period, respectively, the consortium with the five species showed a biodegradation rate of 63.61%, below rate of one of the isolates individually. With high potential for biodegradation, the INPA R557 and INPA R677 isolates can be used for bio-augmentation techniques in soil in a clearing environment for the bioremediation of oil and its derivatives, since during the 21-day period, the levels of n-alkanes, HPA and compounds were reduced more complex, such as methyl styrene.