Isolation and characterization of a bacterial consortium with high ability to simultaneously remove phenol and chromium

ONTAÑÓN, O; GONZALEZ P; MEDINA MI; AGOSTINI E

Mar del Plata

Congreso; VIII Congreso Argentino de Microbiologia SAMIGE; 2012

SAMIGE

According to the U. S. Environmental Protection Agency?s National Priority List (NPL), forty percent of the hazardous waste sites are co-contaminated with organic pollutants and metals. Although bioremediation has taken great importance in the last years, few biological systems are described for their ability to simultaneously remediate toxic organic compounds and heavy metals. For this reason, the aim of the present work was to isolate and characterize pure or mixed microbial cultures capable to grow with high phenol and chromium concentrations from tannery effluents and sediments of a polluted area, located in Elena (Córdoba). Thirty percent of the isolated microorganisms tolerated concentrations higher than 350 mg/l of phenol and 70 mg/l of chromium (VI). This group of microorganisms was mostly constituted by Gram negative bacilli and coccobacilli, and three isolates were mixed cultures. All isolates were analyzed for their capabilities to remove phenol and to reduce Cr (VI), independently and simultaneously in liquid medium. The highest removal of both compounds was achieved by 2 mixed cultures. Among them, the consortium SFC 500-1 was selected as the most efficient system.  Bacterial strains of this consortium were identified as Acinetobacter sp. and Bacillus sp., on the basis of morphological and biochemical properties, 16S rRNA gene sequencing and phylogenetic analysis. SFC 500-1 was able to completely remove high phenol concentrations (100 to 1000 mg/l) in presence and absence of chromium (VI), in TY and mineral medium. Furthermore, high chromium reduction was achieved in TY medium containing Cr (VI) concentrations from 10 to 100 mg/l. Finally, simultaneous removal of both pollutants was evaluated. In all cases, 100% phenol removal was achieved but just 10 mg/l of chromium was fully reduced in presence of phenol. It was observed that the limiting compound for removal was chromium because its reduction declined with increasing initial concentrations. However, increments on phenol concentration from 100 to 750 mg/l did not affect significantly Cr (VI) removal. The consortium SFC 500-1 showed high removal efficiencies in a wide range of temperature (20ºC to 35ºC), pH (5 to 10) and agitation rate (100 to 250 rpm). In conclusion, these results showed the higher efficiency of mixed cultures compared with pure cultures on phenol and chromium removal and allowed us to select the consortium SFC 500-1 as an interesting system for bioremediation of these pollutants.