title: Hexavalent chromium reduction by chromate-resistant haloalkaliphilicHalomonassp. M-Cr newly isolated from tannery effluent.
abstract: The current study aimed to isolate and characterize a chromate-resistant bacterium from tannery effluent, able to reduce Cr(VI) aerobically at high pH and salinity. Environmental contamination by hexavalent chromium, Cr(VI), presents a serious public health problem. Enrichment led to the isolation of 12 bacteria displaying different degrees of chromate reduction. Phenotypic characterization and phylogenetic analysis based on 16S rDNA sequence comparison indicated that the most potent strain belonged to the genusHalomonas. The new strain designated asHalomonassp. M-Cr was able to reduce 82% of 50 mg L-1Cr(VI) in 48 h, concomitant with discolouring of yellow colour of the medium and formation of white insoluble precipitate of Cr(III). It exhibited growth up to 3500 mg L-1Cr(VI), 20% NaCl and showed strong Cr(VI) reduction under alkaline condition, pH 10. Scanning electron microscopy revealed precipitation of chromium hydroxide on bacterial cell surfaces, which showed characteristic peak of chromium in energy-dispersive X-ray analysis. Plackett-Burman design was used to evaluate the influence of related parameters for enhancing Cr(VI) reduction. Glucose, yeast extract and KH2PO4were confirmed as significant variables in the medium. Data suggestHalomonassp. M-Cr as a promising candidate for bioremediation of Cr(VI) contaminated effluents particularly in saline and alkaline environments. Up to our knowledge, this is the first report on isolation of haloalkaliphilicHalomonassp. from tannery effluent.
authors.affiliation: Botany Department, Faculty of Science, Damanhour University , Damanhour , Egypt.
authors.forename: Mona E M
authors.initials: ME
authors.lastname: Mabrouk
authors.affiliation: Botany Department, Faculty of Science, Damanhour University , Damanhour , Egypt.
authors.forename: Mervat A
authors.initials: MA
authors.lastname: Arayes
authors.affiliation: Botany and Microbiology Department, Faculty of Science, Alexandria University , Alexandria , Egypt.
authors.forename: Soraya A
authors.initials: SA
authors.lastname: Sabry
keywords: Cr(VI) reduction; Halomonas sp. M-Cr; Plackett–Burman design; bioremediation; haloalkaliphilic; scanning electron microscopy