10.1021/es100198v.s001 Yangjian Cheng Yangjian Cheng Fenbo Yan Fenbo Yan Feng Huang Feng Huang Wangsheng Chu Wangsheng Chu Danmei Pan Danmei Pan Zhi Chen Zhi Chen Jinsheng Zheng Jinsheng Zheng Meijuan Yu Meijuan Yu Zhang Lin Zhang Lin Ziyu Wu Ziyu Wu Bioremediation of Cr(VI) and Immobilization as Cr(III) by <i>Ochrobactrum anthropi</i> American Chemical Society 2010 coordination Ochrobactrum anthropi system cell debris Cr 2010-08-15 00:00:00 Journal contribution https://acs.figshare.com/articles/journal_contribution/Bioremediation_of_Cr_VI_and_Immobilization_as_Cr_III_by_i_Ochrobactrum_anthropi_i_/2742910 Bioremediation of Cr(VI) through reduction relies on the notion that the produced Cr(III) may be precipitated or efficiently immobilized. However, recent reports suggest that soluble organo-Cr(III) complexes are present in various chromate-reducing bacterial systems. This work was designed to explore the factors that affect the immobilization of Cr(III) in the <i>Ochrobactrum anthropi</i> system. X-ray absorption fine structure analysis on the cell debris clearly verified that coordination of Cr(III) occurs on the surfaces via the chelating coordination with carboxyl- and amido-functional groups. However, competitive coordination experiments of Cr(III) revealed that the small molecules such as amino acids and their derivatives or multicarboxyl compounds hold stronger coordination ability with Cr(III) than with cell debris. We speculate that it is the preferential coordination of Cr(III) to the soluble organic molecules in the bacterial culture medium that inhibits effective immobilization of Cr(III) on the cells. On the basis of this understanding, a strategy with two-step control of the medium was proposed, and this achieved successful immobilization of Cr(VI) as Cr(III) by <i>O. anthropi</i> and <i>Planococcus citreus</i> in 5−50 L pilot-scale experiments.