Bioreduction of Cr(VI) by Indigenously Isolated Bacterial Strains from Stream Sediment Contaminated with Tannery Waste.

The potential of indigenously isolated bacteria from the Estância Velha stream to reduce Cr(VI) was evaluated and also the chromium contamination over the past ten years was verified in one of the most important industrial centers of Brazil, the "Brazilian Capital of Tanneries," Estância Velha municipality in the Rio Grande do Sul State, South Brazil. Samples were collected from the Estância Velha stream at the source (P1), as well as at upstream (P2) and downstream (P3) of the most demographically area. The bacterial strains reduced between 52.5 and 61.6% of 250 mg L ^-1 Cr(VI) in 48 h. The genus Acinetobacter was the most abundant and could efficiently reduce 500 mg L ^-1 of Cr(VI); for example, P2.8 and P2.9 strains of Acinetobacter ursingii reduced 21.3 and 24.5% of 500 mg L ^-1 of Cr(VI), respectively, after 48 h. Moreover, an analysis of Cr levels in the stream sediment reported up to 3594 mg. L ^-1 of total Cr and up to 138 mg. L ^-1 of Cr(VI) in 2009. Acinetobacter strains were identified as the most abundant and efficient in reducing Cr(VI), makes them an ideal candidate for cleaning environments contaminated with tannery effluents, an approach that is more cost-effective than the traditional methods.