Journal of Microbiology

Journal Article

Cr(VI) removal from aqueous solution by thermophilic denitrifying bacterium Chelatococcus daeguensis TAD1 in the presence of single and multiple heavy metals: Han Li , Shaobin Huang , Yongqing Zhang; J. Microbiol. 2016;54(9):602-610. Published online August 31, 2016; DOI: https://doi.org/10.1007/s12275-016-5295-5

Abstract: Cr(VI) pollution is increasing continuously as a result of ongoing industrialization. In this study, we investigated the thermophilic denitrifying bacterium Chelatococcus daeguensis TAD1, isolated from the biofilm of a biotrickling filter used in nitrogen oxides (NOX) removal, with respect to its ability to remove Cr(VI) from an aqueous solution. TAD1 was capable of reducing Cr(VI) from an initial concentration of 10 mg/L to non-detectable levels over a pH range of 7–9 and at a temperature range of 30–50°C. TAD1 simultaneously removed both Cr(VI) and NO3 −-N at 50°C, when the pH was 7 and the initial Cr(VI) concentration was 15 mg/L. The reduction of Cr(VI) to Cr(III) correlated with the growth metabolic activity of TAD1. The presence of other heavy metals (Cu, Zn, and Ni) inhibited the ability of TAD1 to remove Cr(VI). The metals each individually inhibited Cr(VI) removal, and the extent of inhibition increased in a cooperative manner in the presence of a combination of the metals. The addition of biodegradable cellulose acetate microspheres (an adsorption material) weakened the toxicity of the heavy metals; in their presence, the Cr(VI) removal efficiency returned to a high level. The feasibility and applicability of simultaneous nitrate removal and Cr(VI) reduction by strain TAD1 is promising, and may be an effective biological method for the clean-up of wastewater.

Research Support, Non-U.S. Gov't

Purification and Characterization of NADPH-Dependent Cr(VI) Reductase from Escherichia coli ATCC 33456: Woo-Chul Bae , Han-Ki Lee , Young-Chool Choe , Deok-Jin Jahng , Sang-Hee Lee , Sang-Jin Kim , Jung-Hyun Lee , Byeong-Chul Jeong; J. Microbiol. 2005;43(1):21-27.; DOI: https://doi.org/2143 [pii]

Abstract: A soluble Cr(VI) reductase was purified from the cytoplasm of Escherichia coli ATCC 33456. The molecular mass was estimated to be 84 and 42 kDa by gel filtration and SDS-polyacrylamide gel electrophoresis, respectively, indicating a dimeric structure. The pI was 4.66, and optimal enzyme activity was obtained at pH 6.5 and 37^oC. The most stable condition existed at pH 7.0. The purified enzyme used both NADPH and NADH as electron donors for Cr(VI) reduction, while NADPH was the better, conferring 61% higher activity than NADH. The K_m values for NADPH and NADH were determined to be 47.5 and 17.2 umol, and the V_max values 322.2 and 130.7 umol Cr(VI) min^-1mg^-1 protein, respectively. The activity was strongly inhibited by N-ethylmalemide, Ag^2+, Cd^2+, Hg^2+, and Zn^2+. The antibody against the enzyme showed no immunological cross reaction with those of other Cr(VI) reducing strains.

Reduction of Hexavalent Chromium by Escherichia coli ATCC 33456 in Batch and Continuous Cultures: Woo Chul Bae , Tae Gu Kang , In Kyong Kang , You Jung Won , Byeong Chul Jeong; J. Microbiol. 2000;38(1):36-39.

Abstract: Toxic hexavalent chromium, Cr(VI), was reduced to a less toxic trivalent chromium form by E. coli ATCC 33456. The suitable electron donor for Cr(VI) reduction was glucose. E. coli ATCC 33456 was more resistant to metal cations than other reported Cr(VI) reducing microorganisms. Cell growth was inhibited by the presence of Cr(VI) in a liquid medium and Cr(VI) reduction accompanied cell growth. With a hydraulic retention time of 20 h, Cr(VI) reducing efficiency was 100% to 84% when Cr(VI) concentration in the influent was in the range of 10 to 40 mg L^-1. Specific rate of Cr(VI) concentration in the influent was 2.41 mg Cr(VI) g DCW^-1 h^-1 when 40 mg :^-1 of Cr(VI) influent was used. This result suggested the potential application of E. coli ATCC 33456 for the detoxification of Cr(VI) in Cr(VI) contaminated wastewater.

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