Chromium (VI) bioremediation by a bacterial strain isolated from tannery sediments.

AMBROSIO, L; PAISIO CE; ONTAÑÓN, O; AGOSTINI E; GONZALEZ PS

Mar del Plata

Congreso; VIII Congreso Argentino de Microbiologia General SAMIGE; 2012

SAMIGE

Chromium is used in several industrial processes such as steel and iron production, tanning of leather, petroleum refining and others. The industrial effluents generated are frequently released to water sources, mainly without previous treatment, producing serious environmental and anthropological problems, due to its high toxicity. In this sense, bioremediation constitutes a possible alternative to remediate contaminated environments. The aims of this research were: a) to identify and characterize a strain isolated from tannery sediments, using biochemical and molecular methods, b) to evaluate the capability of the isolated strain to tolerate and reduce Cr (VI), c) to determinate optimum conditions of pH, temperature, medium composition, carbon source and initial inoculum concentration to obtain the highest efficiency of the process. The strain namely C8 was characterized as a Gram positive, catalase-positive, oxidase-negative bacterium. Several biochemical tests were performed in order to characterize the strain. This was identified as Serratia sp. by 16S rDNA gene PCR amplification. The strain was able to tolerate until 175 mg/l Cr (VI) in rich medium (TY) and 50 mg/l in mineral medium. Chromium reduction was carried out in both liquid culture media. C8 strain was able to reduce almost completely 5 mg/l, 55% of 20 mg/l and 50% of 50 mg/l in TY medium. To determine the optimum conditions for Cr (VI) reduction, sodium acetate, sucrose, glucose and citric acid were added to TY medium. Different pH (4-9), temperature (20-40 °C) and initial inoculum concentrations (1-10%) were assayed. Serratia sp could reduce 75% of 20 mg/l Cr (VI), in a medium containing 1 g/l of glucose, at pH 6-7, in broad range of temperature, as optimal conditions, using 5% inoculum concentration. In conclusion, Serratia sp. could be a suitable microorganism for Cr (VI) bioremediation of tannery sediments and effluents or even in other environments contaminated with chromium.