title: Reduction of Cr(VI) by Escherichia coli BL21 in the presence of redox mediators.
abstract: Anthraquinone-2,7-disulfonate (2,7-AQDS), anthraquinone-1-sulfonate (α-AQS), anthraquinone-2-sulfonate (AQS), anthraquinone-2,6-disulfonate (AQDS) and anthraquinone-1,5-disulfonate (1,5-AQDS) were selected as redox mediators for Cr(VI) reduction by Escherichia coli BL21. In the presence of 0.8mmoll(-1) AQS, the Cr(VI) reduction efficiency was 98.5% in 7.5h, whereas it was only 21-34% in the absence of a mediator or in the presence of α-AQS, 1,5-AQDS, AQDS, 2,7-AQDS. A linear correlation, k=0.768C(AQS)+1.5531 (R(2)=0.9935), was found for the reaction constant, k (mg Cr(VI) g(-1) dry cell weight h(-1)) and the AQS concentration (C(AQS)). The Arrhenius equation described the Cr(VI) reduction in the tested temperature range, and the pre-exponential factor A was 13.249mg Cr(VI) g(-1) dry cell weight h(-1),and the activation energy Ea was 28.01kJmol(-1). Glucose was the best carbon sources, and the optimum pH was 6.0. The Cr(VI) reduction rate obtained with AQS is a significant improvement over low conventional anaerobic reduction rates.
authors.affiliation: School of Environmental Science and Engineering, Hebei University of Science and Technology, Yuhua East Road 70#, Shijiazhuang 050018, China. jianbguo@yahoo.com.cn
authors.forename: Jianbo
authors.initials: J
authors.lastname: Guo
authors.forename: Jing
authors.initials: J
authors.lastname: Lian
authors.forename: Zhifang
authors.initials: Z
authors.lastname: Xu
authors.forename: Zhenhua
authors.initials: Z
authors.lastname: Xi
authors.forename: Jingliang
authors.initials: J
authors.lastname: Yang
authors.forename: William
authors.initials: W
authors.lastname: Jefferson
authors.forename: Chun
authors.initials: C
authors.lastname: Liu
authors.forename: Zaixing
authors.initials: Z
authors.lastname: Li
authors.forename: Lin
authors.initials: L
authors.lastname: Yue
mesh_terms: D000880:Anthraquinones / Q000494:pharmacology*; D001673:Biodegradation, Environmental / Q000187:drug effects; D002244:Carbon / Q000494:pharmacology; D002857:Chromium / Q000378:metabolism*; D004926:Escherichia coli / Q000187:drug effects* / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration / Q000187:drug effects; D010084:Oxidation-Reduction / Q000187:drug effects; D013696:Temperature
chemical_list: D000880:Anthraquinones; D002857:Chromium; C074702:chromium hexavalent ion; C023554:anthraquinone sulfonate; D002244:Carbon