title: Simultaneous decolorization of sulfonated azo dyes and reduction of hexavalent chromium under high salt condition by a newly isolated salt-tolerant strain Bacillus circulans BWL1061.
abstract: The co-existence of dyes, Cr(VI) and high concentration of salt in dyeing wastewater causes serious and complex environmental problems. In this study, a salt-tolerant strain Bacillus circulans BWL1061 was reported to simultaneously remove 50mg/L methyl orange and 50mg/L Cr(VI) under the anaerobic condition with 60g/L NaCl. During the decolorization process, the Cr(VI) reduction occurred preferentially over the dye decolorization due to the dominate utilization of electron by Cr(VI). The analysis of enzyme activities suggested that azoreductase, NADH-DCIP reductase, and laccase were associated with decolorization of methyl orange. A possible degradation pathway was proposed based on the metabolites analysis. The decolorization of methyl orange is involved in the symmetric cleavage of azo bond, which formed N,N-dimethyl p-phenylenediamine and 4-amino sulfonic acid, or the asymmetric cleavage of azo bond, which formed 4-(dimethylamino) phenol and 4-diazenylbenzene sulfonic acid. Phytotoxicity assays showed that strain BWL1061 could decrease the toxicity of methyl orange to Triticum aestivum, Pogostemon cablin and Isatis indigotica Fort during the decolorization process. In this study, Bacillus circulans is reported for the first time that could simultaneously remove azo dyes and Cr (VI) under high salt condition.
authors.affiliation: School of Life Science, The Key Laboratory of Biotechnology for Medicinal Plant of Jiangsu Province, Jiangsu Normal University, Xuzhou 221116, Jiangsu Province, China. Electronic address: leonliu2013@126.com.
authors.forename: Weijie
authors.initials: W
authors.lastname: Liu
authors.affiliation: School of Life Science, The Key Laboratory of Biotechnology for Medicinal Plant of Jiangsu Province, Jiangsu Normal University, Xuzhou 221116, Jiangsu Province, China.
authors.forename: Cong
authors.initials: C
authors.lastname: Liu
authors.affiliation: School of Life Science, The Key Laboratory of Biotechnology for Medicinal Plant of Jiangsu Province, Jiangsu Normal University, Xuzhou 221116, Jiangsu Province, China.
authors.forename: Liang
authors.initials: L
authors.lastname: Liu
authors.affiliation: School of Life Science, The Key Laboratory of Biotechnology for Medicinal Plant of Jiangsu Province, Jiangsu Normal University, Xuzhou 221116, Jiangsu Province, China.
authors.forename: Yanting
authors.initials: Y
authors.lastname: You
authors.affiliation: School of Life Science, The Key Laboratory of Biotechnology for Medicinal Plant of Jiangsu Province, Jiangsu Normal University, Xuzhou 221116, Jiangsu Province, China.
authors.forename: Jihong
authors.initials: J
authors.lastname: Jiang
authors.affiliation: School of Life Science, The Key Laboratory of Biotechnology for Medicinal Plant of Jiangsu Province, Jiangsu Normal University, Xuzhou 221116, Jiangsu Province, China.
authors.forename: Zhengkun
authors.initials: Z
authors.lastname: Zhou
authors.affiliation: School of Life Science, The Key Laboratory of Biotechnology for Medicinal Plant of Jiangsu Province, Jiangsu Normal University, Xuzhou 221116, Jiangsu Province, China.
authors.forename: Zhen
authors.initials: Z
authors.lastname: Dong
mesh_terms: D000693:Anaerobiosis; D001391:Azo Compounds / Q000032:analysis* / Q000737:chemistry; D001407:Bacillus / Q000201:enzymology / Q000254:growth & development* / Q000378:metabolism; D001673:Biodegradation, Environmental; D002857:Chromium / Q000032:analysis* / Q000737:chemistry; D004396:Coloring Agents / Q000032:analysis* / Q000737:chemistry; D042845:Laccase / Q000378:metabolism; D009247:NADH, NADPH Oxidoreductases / Q000378:metabolism; D009601:Nitroreductases; D011808:Quinone Reductases / Q000378:metabolism; D055049:Salt Tolerance; D012965:Sodium Chloride / Q000378:metabolism; D062065:Wastewater / Q000737:chemistry; D018508:Water Purification / Q000379:methods*
chemical_list: D001391:Azo Compounds; D002857:Chromium; D004396:Coloring Agents; D042845:Laccase; D009247:NADH, NADPH Oxidoreductases; D009601:Nitroreductases; D011808:Quinone Reductases; D012965:Sodium Chloride; D062065:Wastewater; C074702:chromium hexavalent ion; C100258:methyl orange; C033633:dichlorophenolindophenol reductase; C021106:azoreductase
keywords: Azo dye; Azoreductase; Bacillus circulans; Decolorization; Hexavalent chromium; Methyl orange