Application of an immobilized bacterial consortium for xenobiotics bioremediation.

ONTAÑON ORNELLA M.; GONZÁLEZ, PAOLA S.,; AGOSTINI ELIZABETH

Workshop; II Workshop Latinoamericano sobre PGPR; 2014

Application of an immobilized bacterial consortium for xenobiotics bioremediation Ontañon O., González P., Agostini E. Departamento de Biología Molecular. Universidad Nacional de Río Cuarto, Río Cuarto, Argentina. Contact: pgonzalez@exa.unrc.edu.ar Bioremediation is an eco-friendly strategy to deal with environmental pollution. Since the majority of polluted sites contain complex mixtures of chemicals, including both inorganic and organic pollutants, it is important to find bacterial strains that can cope with multiple contaminants. For that, we employed the native consortium SFC 500-1 for the simultaneous remediation of Cr (VI) and phenol. SFC 500-1 was isolated from polluted soils and it is composed by two bacterial strains belonging to Acinetobacter and Bacillus genera. Many species from both genera have shown PGPB properties and interesting capabilities for pollutants bioremediation. The consortium SFC 500-1 was immobilized in a 3% Ca-alginate matrix and used for Cr (VI) and phenol simultaneous removal. Some parameters involved in removal were optimized and the formed products were detected by colorimetric techniques, atomic absorption spectrometry and HPLC. The removal efficiency of immobilized cells was compared to that obtained using free cells. Immobilized cells (1.5 X 109 CFU/ml) of SFC 500-1 removed high concentrations of both contaminants, employing phenol as the only carbon source in saline solution. The addition of glucose (0.3%) and the pre-adaptation of the consortium to the pollutants significantly improved the bioremediation process. The immobilized consortium reduced Cr (VI) to Cr (III) and degraded phenol to catechol and cis-cis-muconate, typical metabolites obtained by bacterial phenol oxidation. At the optimal conditions, the immobilized cells removed up to 15.5 mg/l of Cr (VI) and 300 mg/l of phenol after 6 h. However, free cells required 12 h to remove the same phenol concentrations and 10 mg/l of Cr (VI). Alginate beads were reutilized up to 5 cycles of removal, but their efficiency was significantly affected from the third reuse. SFC 500-1 degraded phenol up to 1,000 mg/l in the presence of Cr (VI) both in immobilized and free conditions, but the highest degradation rates were achieved with immobilized cells. Furthermore, immobilized consortium was able to fully remove even 1,500 mg/l of phenol, but free cells didn´t tolerate such concentration. The entrapped cells were also more efficient for Cr (VI) reduction, independently of incorporated phenol concentration. Thus, a protective effect of the alginate matrix on bacterial biomass was observed and cellular death was lower using immobilized cells than using free cells. The results indicated that SFC 500-1 has a potential to simultaneously remove Cr (VI) and phenol, and to decrease their toxicity through the biological process of reduction and mineralization, respectively. Therefore, biotransformation catalyzed by SFC 500-1 could be used as an effective biotechnological strategy to clean up co-polluted waters. Additionally, the presence of high concentrations of Cr (VI) and phenol have also been reported in soils from industrialized countries. This situation is a serious problem since it is known that these pollutants may be uptaken by plant roots, translocated to aerial parts and even they can enter to the food chain. On the basis of our recent findings, we propose using the immobilized consortium SFC 500-1 for the treatment of contaminated soils in order to contribute to the plant tolerance. These studies will be conducted in our laboratory.