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3 Polish Journal of Microbiology

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Enterobacter asburiae KUNi5, a nickel resistant bacterium for possible bioremediation of nickel contaminated sites

100%

Paul A. , Mukherjee S. K.

Polish Journal of Microbiology

2016

tom 65

nr 1

Nickel resistant bacterial strain Enterobacter asburiae KUNi5 was isolated and showed resistance up to 15 mM and could remove Ni optimally better at 37°C and pH 7. Maximum removal was found at initial concentration of 0.5 to 2 mM, however, growth and Ni removal were affected by other heavy metals. Major amount of the metal was accumulated in the membrane fractions and certain negatively charged groups were found responsible for Ni binding. KUNi5 could also produce 1-aminocyclopropane-1-carboxylate deaminase, indole-acetic acid and siderophore. It seems that KUNi5 could be a possible candidate for Ni detoxification and plant growth promotion in Ni-contaminated field.

Chromate reduction by cell-free extract of Bacillus firmus KUCr1

80%

Sau G. B. , Chatterjee S. , Mukherjee S. K.

Polish Journal of Microbiology

2010

tom 59

nr 3

Microbial enzymatic reduction of a toxic form of chromium [Cr(VI)] has been considered as an effective method for bioremediation of this metal. This study reports on the in vitro reduction of Cr(VI) using cell-free extracts from a Cr(VI) reducing Bacillusfirmus KUCr1 strain. Chromium reductase was found to be constitutive and its activity was observed both in soluble cell fractions (S₁₂and S₁₅₀) and membrane cell fraction (P₁₅₀). The reductase activity of S₁₂ fraction was found to be optimal at 40 μM Cr(VI) with enzyme concentration equivalent to 0.493 mg protein/ml. Enzyme activity was dependent on NADH or NADPH as electron donor; optimal temperature and pH for better enzyme activity were 70°C and 5.6, respectively. The Km value of the reductase was 58.33 μM chromate having a Vmax of 11.42 μM/min/mg protein. The metabolic inhibitor like sodium azide inhibited reductase activity of membrane fraction of the cell-free extract. Metal ions like Cu²⁺, Co²⁺, Ni²⁺ and As³⁺ stimulated the enzyme but others, such as Ag⁺, Hg²⁺, Zn²⁺, Mn²⁺, Cd²⁺ and Pb²⁺, inhibited Cr(VI) reductase activity.

Isolation and characterization of a Cr[VI] reducing Bacillus firmus strain from industrial effluents

80%

Sau G. B. , Chatterjee S. , Sinha S. , Mukherjee S. K.

Polish Journal of Microbiology

2008

tom 57

nr 4

A chromium resistant bacterial strain KUCr1 exhibiting potential Cr(VI) reducing ability under in vitro aerobic condition is reported. The bacterial strain showed varied degree of resistance to different heavy metals. The MIC of chromium to this strain was found to be 950 mM under aerobic culture condition in complex medium. The factors affecting Cr(VI) reduction by this strain under culture condition were evaluated. Maximal Cr(VI) reduction was observed at the pH 8 to 10 and at a temperature of 35°C. Higher concentration of Cr(VI) slowed down the reduction, eventually all the metal could be reduced with longer incubation time. Different toxic metals showed differential effect on reduction. Cadmium and zinc were found to inhibit reduction. Cr(VI) reduction and bioremediation were found to be related to the growth supportive condition in terms of carbon, phosphorous and nitrogen supply in wastewater fed with tannery effluent indicating cell mass dependency of Cr(VI) reduction. Through biochemical characterization and 16S rDNA sequence analysis, the strain KUCr1, as the name given to it, was identified as a strain of Bacillus firmus.