Mechanisms involved in chromium (VI) removal by Serratia sp. C8

AMBROSIO, LAURA FERNANDA; PAISIO, CINTIA ELIZABETH; ONTAÑON, ORNELLA MAILEN; AGOSTINI ELIZABETH; GONZALEZ, PAOLA SOLANGE

Mar del Plata

Congreso; XI Congreso de Microbiología General; 2013

Different processes by which microorganisms remove chromium (Cr VI) have been described, including bioadsorption, bioaccumulation and enzymatic reduction to the less toxic form Cr (III). The present work deals with the study of the mechanisms involved in Cr (VI) removal in Serratia sp. C8, a strain previously isolated from tannery sediments with ability to tolerate and reduce this heavy metal. Two different methodologies (cell inactivation by heat and acid pH) were used to demonstrate that the strain was capable to bioadsorb around 7.5-8.5% of 10 mg/l Cr on their surface. Extracellular chromate reductase activity was not detected in Serratia sp. C8, however the results suggested that the enzyme would be present in cytoplasm, since the soluble fraction was responsible of 34% Cr (VI) reduction. To determine the final localization of initially incorporated Cr (VI) to the culture media, total Cr (Cr VI and Cr III) was determined in biomass and supernatant. Approximately 46 and 54% of total chromium was detected in supernatant and in the biomass, respectively. The metal accumulated in the cells would be probably in the state of Cr (III), which could be associated to the catalytic activity of intracellular chromate reductase. In conclusion, the mechanisms involved in Cr (VI) removal by Serratia sp. C8 were bioadsoption to the biomass and reduction catalyzed by an intracellular chromate reductase.