共查询到20条相似文献,搜索用时 31 毫秒
1.
Okeke BC 《Journal of industrial microbiology & biotechnology》2008,35(12):1571-1579
Pollution of terrestrial surfaces and aquatic systems by hexavalent chromium, Cr(VI), is a worldwide public health problem.
A chromium resistant bacterial isolate identified as Exiguobacterium sp. GS1 by 16S rRNA gene sequencing displayed high rate of removal of Cr(VI) from water. Exiguobacterium sp. GS1 is 99% identical to Exiguobacterium acetylicum. The isolate significantly removed Cr(VI) at both high and low concentrations (1–200 μg mL−1) within 12 h. The Michaelis–Menten K
m
and V
max for Cr(VI) bioremoval were calculated to be 141.92 μg mL−1 and 13.22 μg mL−1 h−1, respectively. Growth of Exiguobacterium sp. GS1 was indifferent at 1–75 μg mL−1 Cr(VI) in 12 h. At initial concentration of 8,000 μg L−1, Exiguobacterium sp. GS1 displayed rapid bioremoval of Cr(VI) with over 50% bioremoval in 3 h and 91% bioremoval in 8 h. Kinetic analysis
of Cr(VI) bioremoval rate revealed zero-order in 8 h. Exiguobacterium sp. GS1 grew and significantly reduced Cr(VI) in cultures containing 1–9% salt indicating high salt tolerance. Similarly
the isolate substantially reduced Cr(VI) over a wide range of temperature (18–45 °C) and initial pH (6.0–9.0). The T
opt and initial pHopt were 35–40 °C and 7–8, respectively. Exiguobacterium sp. GS1 displayed a great potential for bioremediation of Cr(VI) in diverse complex environments. 相似文献
2.
A hexavalent chromium [Cr(VI)] reducing bacterial strain was isolated from chromium-containing slag. It was identified as
Pannonibacter phragmitetus based on physiological, biochemical characteristics and 16S rRNA gene sequence analysis. This bacterium displayed great Cr(VI)
reduction capability. The Cr(VI) could be completely removed in 24 h under anaerobic condition when the initial concentration
was 1,917 mg L−1, with the maximum reduction rate of 562.8 mg L−1 h−1. The Cr(VI) reduction rate increased with the increase of Cr(VI) concentration. P. phragmitetus was able to use many carbon sources such as lactose, fructose, glucose, pyruvate, citrate, formate, lactate, NADPH and NADH
as electron donors, among which the lactate had the greatest power to promote the reduction process. Zn2+, Cd2+ and Ni2+ inhibited, while Cu2+, Pb2+, Mn2+ and Co2+ stimulated the reduction. The optimum pH and temperature for reduction were 9.0 and 30 °C, respectively. The results indicated
that this strain had great potential for application in the bioremediation of chromate-polluted soil and water systems. 相似文献
3.
Jinxia Yang Minyan He Gejiao Wang 《World journal of microbiology & biotechnology》2009,25(9):1579-1587
Chromate-reducing microorganisms with the ability of reducing toxic chromate [Cr(VI)] into insoluble trivalent chromium [Cr(III)]
are very useful in treatment of Cr(VI)-contaminated water. In this study, a novel chromate-reducing bacterium was isolated
from Mn/Cr-contaminated soil. Based on morphological, physiological/biochemical characteristics and 16S rRNA gene sequence
analyses, this strain was identified as Intrasporangium sp. strain Q5-1. This bacterium has high Cr(VI) resistance with a MIC of 17 mmol l−1 and is able to reduce Cr(VI) aerobically. The best condition of Cr(VI) reduction for Q5-1 is pH 8.0 at 37°C. Strain Q5-1
is also able to reduce Cr(VI) in resting (non-growth) conditions using a variety of carbon sources as well as in the absence
of a carbon source. Acetate (1 mmol l−1) is the most efficient carbon source for stimulating Cr(VI) reduction. In order to apply strain Q5-1 to remove Cr(VI) from
wastewater, the bacterial cells were immobilized with different matrices. Q5-1 cells embedded with compounding beads containing
4% PVA, 3% sodium alginate, 1.5% active carbon and 3% diatomite showed a similar Cr(VI) reduction rates to that of free cells.
In addition, the immobilized Q5-1 cells have the advantages over free cells in being more stable, easier to re-use and minimal
clogging in continuous systems. This study provides potential applications of a novel immobilized chromate-reducing bacterium
for Cr(VI) bioremediation. 相似文献
4.
Bacterial consortium-AIE2 with a capability of contemporaneous Cr(VI) reduction and azo dye RV5 decolourization was developed
from industrial wastewaters by enrichment culture technique. The 16S rRNA gene based molecular analyses revealed that the
consortium bacterial community structure consisted of four bacterial strains namely, Alcaligenes sp. DMA, Bacillus sp. DMB, Stenotrophomonas sp. DMS and Enterococcus sp. DME. Cumulative mechanism of Cr(VI) reduction by the consortium was determined using in vitro Cr(VI) reduction assays.
Similarly, the complete degradation of Reactive Violet 5 (RV5) dye was confirmed by FTIR spectroscopic analysis. Consortium-AIE2
exhibited simultaneous bioremediation efficiencies of (97.8 ± 1.4) % and (74.1 ± 1.2) % in treatment of both 50 mg l−1 Cr(VI) and RV5 dye concentrations within 48 h of incubation at pH 7 and 37°C in batch systems. Continuous bioreactor systems
achieved simultaneous bioremediation efficiencies of (98.4 ± 1.5) % and (97.5 ± 1.4) % after the onset of steady-state at
50 mg l−1 input Cr(VI) and 25 mg l−1 input RV5 concentrations, respectively, at medium dilution rate (D) of 0.014 h−1. The 16S rRNA gene copy numbers in the continuous bioreactor as determined by real-time PCR assay indicated that Alcaligenes sp. DMA and Bacillus sp. DMB dominated consortium bacterial community during the active continuous bioremediation process. 相似文献
5.
A Bacillus sp. RE was resistant to chromium and reduced Cr(VI) without accumulating chromium inside the cell. When Cr(VI) was 10 and
40 μg ml−1, >95% of the total Cr(VI) was reduced in 24 and 72 h of growth, respectively, whereas at 80 μg Cr(VI) ml−1 only 50% of Cr(VI) was reduced. However growth was not affected; the cell mass was 0.7–0.8 mg ml−1 in all cases. The cell-free extract showed Cr(VI) reducing enzyme activity which was enhanced (>5 fold) by NADH and NADPH.
Like whole cells the enzyme also reduced Cr(VI) with decreasing efficiency on increasing Cr(VI) concentration. The enzyme
activity was optimal at pH 6.0 and 30 °C. The enzyme was stable up to 30 °C and from pH 5.5 to 8, but from pH 4 to 5 the enzyme
was severely destabilized. Its Km and Vmax were 14 μm and 3.8 nmol min−1 mg−1 respectively. The enzyme activity was enhanced by Cu2+ and Ni2+ and inhibited by Hg2+.
Received 21 September 2005; Revisions requested 5 October 2005; Revisions received 16 November 2005; Accepted 16 November
2005 相似文献
6.
Vatsouria A Vainshtein M Kuschk P Wiessner A D K Kaestner M 《Journal of industrial microbiology & biotechnology》2005,32(9):409-414
Industrial wastewater is often polluted by Cr(VI) compounds, presenting a serious environmental problem. This study addresses
the removal of toxic, mutagenic Cr(VI) by means of microbial reduction to Cr(III), which can then be precipitated as oxides
or hydroxides and extracted from the aquatic system. A strain of Staphylococcus epidermidis L-02 was isolated from a bacterial consortium used for the remediation of a chromate-contaminated constructed wetland system.
This strain reduced Cr(VI) by using pyruvate as an electron donor under anaerobic conditions. The aims of the present study
were to investigate the specific rate of Cr(VI) reduction by the strain L-02, the effects of chromate and nitrate (available
as electron acceptors) on the strain, and the interference of chromate and nitrate reduction processes. The presence of Cr(VI)
decreased the growth rate of the bacterium. Chromate and nitrate reduction did not occur under sterile conditions but was
observed during tests with the strain L-02. The presence of nitrate increased both the specific Cr(VI) reduction rate and
the cell number. Under denitrifying conditions, Cr(VI) reduction was not inhibited by nitrite, which was produced during nitrate
reduction. The average specific rate of chromate reduction reached 4.4 μmol Cr 1010 cells−1 h−1, but was only 2.0 μmol Cr 1010 cells−1 h−1 at 20 °C. The maximum specific rate was as high as 8.8–9.8 μmol Cr 1010 cells−1 h−1. The role of nitrate in chromate reduction is discussed. 相似文献
7.
A novel system combining acoustic wave impedance (AWI) analyzer with UV-vis spectrophotometer was developed for the study
of chromium (VI) reduction kinetics by Pseudomonas aeruginosa. AWI gave information about the growth of Pseudomonas aeruginosa, and UV-vis spectrophotometer gave information about the concentration of chromium (VI) simultaneously. A combined system
response model, for chromium (VI) reduction kinetics at lower initial chromium (VI) concentrations, was derived and proved
based on the novel system. Taking into account the effect of bacterial growth on chromium (VI) reduction, the new model successfully
simulated chromium (VI) bioremediation process. By fitting chromium (VI) reduction data toward the derived model, the kinetic
parameters related to the process were obtained. When the concentration of peptone was 10 g L−1, the half-velocity reduction rate constant K
C and the maximum specific chromium (VI) reduction rate constant νmax were 0.7682 mg chromium (VI) L−1 and 2.5814 × 10−12 mg chromium (VI) cells−1 h−1, respectively. It was found that the combined system can provide real-time, reliable, and two-dimensional kinetic information,
and can be applied to study other biological processes. 相似文献
8.
Chromium(VI) resistance and removal by <Emphasis Type="Italic">Acinetobacter haemolyticus</Emphasis>
Quek Hsiao Pei Shafinaz Shahir A. S. Santhana Raj Zainul Akmar Zakaria Wan Azlina Ahmad 《World journal of microbiology & biotechnology》2009,25(6):1085-1093
The present work highlighted the studies on Cr(VI) reduction by cells of Acinetobacter haemolyticus (A. haemolyticus). The strain tolerated 90 mg Cr(VI) l−1 in LB broth compared to only 30 mg Cr(VI) l−1 in LB agar. From the FTIR analysis, the Cr(III) species formed was also most likely to form complexes with carboxyl, hydroxyl,
and amide groups from the bacteria. A TEM study showed the absence of precipitates on the cell wall region of the bacteria.
Instead, microprecipitates were observed in the cytoplasmic region of the cells, suggesting the transportation of Cr(VI) into
the cells. Intracellular reduction of Cr(VI) was supported by a reductase test using soluble crude cell-free extracts. The
specific reductase activity obtained was 0.52 μg Cr(VI) reduced per mg of protein an hour at pH 7.2 and 37°C. Our results
indicated that A. haemolyticus can be used as a promising microorganism for Cr(VI) reduction from industrial wastewaters. 相似文献
9.
Liping Huang Jingwen Chen Xie Quan Fenglin Yang 《Bioprocess and biosystems engineering》2010,33(8):937-945
Enhancement of Cr (VI) reduction rate and power production from biocathode microbial fuel cells (MFCs) was achieved using
indigenous bacteria from Cr (VI)-contaminated site as inoculum and MFC architecture with a relatively large cathode-specific
surface area of 340–900 m2 m−3. A specific Cr (VI) reduction rate of 2.4 ± 0.2 mg g−1VSS h−1 and a power production of 2.4 ± 0.1 W m−3 at a current density of 6.9 A m−3 were simultaneously achieved at an initial Cr (VI) concentration of 39.2 mg L−1. Initial Cr (VI) concentration and solution conductivity affected Cr (VI) reduction rate, power production and coulombic
efficiency. These findings demonstrate the importance of inoculation and MFC architecture in the enhancement of Cr (VI) reduction
rate and power production. This study is a beneficial attempt to improve the efficiency of biocathode MFCs and provide a good
candidate of bioremediation process for Cr (VI)-contaminated sites. 相似文献
10.
J. D. García-García J. S. Rodríguez-Zavala R. Jasso-Chávez D. Mendoza-Cozatl Rafael Moreno-Sánchez 《Archives of microbiology》2009,191(5):431-440
Photosynthetic Euglena gracilis grown with different K2CrO4 concentrations was analyzed for its ability to take up, retain and reduce Cr(VI). For comparison, cells were also exposed
to CrCl3. Cellular Cr(VI) uptake at pH 7.2 showed a hyperbolic saturation pattern with K
m of 1.1 mM, V
m of 16 nmol (h × 107 cells)−1, and K
i sulfate of 0.4 mM. Kinetic parameters for sulfate uptake were similar, K
m = 0.83 mM, V
m = 15.9 nmol (h × 107cells)−1 and K
i chromate = 0.3 mM. The capacity to accumulate chromium depended on the ionic species, external concentration and pH of the incubation
medium. Cr(VI) or Cr(III) accumulation was negligible in the acidic (pH 3.5) culture medium, in which Cr(VI) was abiotically
reduced to Cr(III). At pH 7.2 Cr(VI) was fully stable and high accumulation (>170 nmol/1 × 107 cells at 1 mM K2CrO4) was achieved; surprisingly, Cr(III) accumulation was also significant (>35 nmol/1 × 107 cells at 1 mM CrCl3). Cr(VI) was reduced by cells at pH 7.2, suggesting the presence of an external reductive activity. Cr(VI) induced an increased
cysteine and glutathione content, but not in phytochelatins suggesting that chromium accumulation was mediated by monothiol
compounds. 相似文献
11.
de María Guillén-Jiménez F Morales-Barrera L Morales-Jiménez J Hernández-Rodríguez CH Cristiani-Urbina E 《Journal of industrial microbiology & biotechnology》2008,35(11):1277-1287
The main aim of this study was to investigate the influence of the sulfate ion on the tolerance to Cr(VI) and the Cr(VI) reduction
in a yeast strain isolated from tannery wastewater and identified as Candida sp. FGSFEP by the D1/D2 domain sequence of the 26S rRNA gene. The Candida sp. FGSFEP strain was grown in culture media with sulfate concentrations ranging from 0 to 23.92 mM, in absence and presence
of Cr(VI) [1.7 and 3.3 mM]. In absence of Cr(VI), the yeast specific growth rate was practically the same in every sulfate
concentration tested, which suggests that sulfate had no stimulating or inhibiting effect on the yeast cell growth. In contrast,
at the two initial Cr(VI) concentrations assayed, the specific growth rate of Candida sp. FGSFEP rose when sulfate concentration increased. Likewise, the greater efficiencies and volumetric rates of Cr(VI) reduction
exhibited by Candida sp. FGSFEP were obtained at high sulfate concentrations. Yeast was capable of reducing 100% of 1.7 mM Cr(VI) and 84% of 3.3 mM
Cr(VI), with rates of 0.98 and 0.44 mg Cr(VI)/L h, with 10 and 23.92 mM sulfate concentrations, respectively. These results
indicate that sulfate plays an important role in the tolerance to Cr(VI) and Cr(VI) reduction in Candida sp. FGSFEP. These findings may have significant implications in the biological treatment of Cr(VI)-laden wastewaters. 相似文献
12.
Evaluation of the bioremoval of Cr(VI) and TOC in biofilters under continuous operation using response surface methodology 总被引:1,自引:0,他引:1
In the present study, the bioremoval of Cr(VI) and the removal of total organic carbon (TOC) were achieved with a system composed
by an anaerobic filter and a submerged biofilter with intermittent aeration using a mixed culture of microorganisms originating
from contaminated sludge. In the aforementioned biofilters, the concentrations of chromium, carbon, and nitrogen were optimized
according to response surface methodology. The initial concentration of Cr(VI) was 137.35 mg l−1, and a bioremoval of 85.23% was attained. The optimal conditions for the removal of TOC were 4 to 8 g l−1 of sodium acetate, >0.8 g l−1 of ammonium chloride and 60 to 100 mg l−1 of Cr(VI). The results revealed that ammonium chloride had the strongest effect on the TOC removal, and 120 mg l−1 of Cr(VI) could be removed after 156 h of operation. Moreover, 100% of the Cr(VI) and the total chromium content of the aerobic
reactor output were removed, and TOC removals of 80 and 87% were attained after operating the anaerobic and aerobic reactors
for 130 and 142 h, respectively. The concentrations of cells in both reactors remained nearly constant over time. The residence
time distribution was obtained to evaluate the flow through the bioreactors. 相似文献
13.
Hexavalent chromium reduction by a dichromate-resistant gram-positive bacterium isolated from effluents of tanneries 总被引:10,自引:0,他引:10
A gram-positive, chromium (Cr)-resistant bacterial strain (ATCC 700729) was isolated from effluent of tanneries. It was grown
in media containing potassium dichromate concentration up to 80 mg ml−1 of the medium. The dichromate reducing capability of the bacterium was checked by estimating the amount of Cr VI in the medium
before and after introduction of bacterial culture. The influence of factors like pH of the medium, concentration of Cr, and
the amount of the inoculum was studied to determine the ability of the bacterium to reduce Cr VI in the medium under various
conditions. In a medium containing dichromate 20 mg ml−1 more than 87% reduction of dichromate ions was achieved within 72 h. The feasibility of the use of this bacterial strain
for detoxification of dichromate in the industrial wastewater has been assessed. The isolated strain can be exploited for
specific environmental clean-up operations.
Received: 7 April 1999 / Accepted: 12 September 1999 相似文献
14.
Wenjie Zhu Zhihui Yang Zemin Ma Liyuan Chai 《World journal of microbiology & biotechnology》2008,24(7):991-996
In recent years, more and more attentions are put on the remediation of Cr(VI) contamination with chromate resistant bacteria.
Leucobacter sp. CRB1 was a novel chromate reducing bacteria isolated from the soil of chromite ore processing residue (COPR) disposal
site in Changsha, China. The objectives of this study were to evaluate the Cr(VI) tolerance of Leucobacter sp. CRB1 as well as its tolerant mechanism, and Cr(VI) reduction ability. The results showed that Leucobacter sp. CRB1 was able to tolerate 4,000 mg/l of hexavalent chromium with 34.5% reduction efficiency. At the optimum pH 9.0, the
maximum concentration of chromate be reduced completely was 1,818 mg/l in growing cells and 2,100 mg/l in resting cells. Scanning
electron microscopy (SEM) and energy dispersive X-ray analysis (EDAX) showed that extracellular Cr(VI) reduction of Leucobacter sp. CRB1 contributed to its high tolerance and high reduction ability. With repeating spiking, 2,490 mg/l hexavalent chromium
was reduced totally within 17 h. The results suggest Leucobacter sp. CRB1 has potential application for remediation of high concentration of Cr(VI) contamination. 相似文献
15.
The plant growth–promoting potentials, production of siderophore and solubilization of insoluble phosphorus (P) and zinc and
lead by the chromium (vi) -reducing Bacillus species, PSB 1, PSB 7, and PSB 10, was assessed both in the presence and absence of chromium under in vitro conditions. The Bacillus strains tolerated chromium up to the concentration of 500 (PSB1), 400 (PSB7), and 550 μg ml−1 (PSB10), respectively, on nutrient agar plates. Bacillus sp. PSB 10 reduced Cr (vi) by 87% at pH 7, which was followed by Bacillus sp. PSB 1 (83%) and PSB 7 (74%) in nutrient broth after 120 h of incubation. A concentration of 50 μg ml−1 of Cr (vi) was completely reduced by Bacillus sp. PSB 1 and PSB 10 (after 100 h) and PSB 7 (after 120 h). The Bacillus strains PSB 1, PSB 7, and PSB 10 produced 19.3, 17.7, and 17.4 μg ml−1 of indole acetic acid, respectively, in luria bertani broth at 100 μg ml−1 of tryptophan, which consistently decreased with an increase in chromium concentration. The Bacillus strains were positive for siderophore, HCN, and ammonia both in the absence and presence of chromium. The Bacillus strains solubilized 375 (PSB 1), 340 (PSB 7), and 379 (PSB 10) μg ml−1 P, respectively, in Pikovskaya broth devoid of chromium. In contrast, chromium at 150 μg ml−1 reduced the amount of P solubilized by 17 (PSB 1), 15 (PSB 7), and 9% (PSB 10) compared to control. The tested bacterial
strains solubilized a considerable amount of zinc and lead in nutrient broth both in the absence and presence of chromium.
Generally, the chromium reduction and the plant growth–promoting potentials of chromium-reducing Bacillus were strongly correlated at the tested concentration of chromium. The present observations demonstrated that the chromium-reducing,
metal-solubilizing, and plant growth–promoting potentials of the Bacillus strains PSB1, PSB 7, and PSB10 were not adversely affected by the chromium application and, hence, may be applied for raising
the productivity of crops under metal-contaminated soils. 相似文献
16.
Yasmin Khambhaty Kalpana Mody Shaik Basha Bhavanath Jha 《World journal of microbiology & biotechnology》2009,25(8):1413-1421
The removal of hexavalent chromium from aqueous solution was studied in batch experiments using dead biomass of three different
species of marine Aspergillus after alkali treatment. All the cultures exhibited potential to remove Cr(VI), out of which, Aspergillus niger was found to be the most promising one. This culture was further studied employing variation in pH, temperature, metal ion
concentration and biomass concentration with a view to understand the effect of these parameters on biosorption of Cr(VI).
Higher biosorption percentage was evidenced at lower initial concentration of Cr(VI) ion, while the sorption capacity of the
biomass increased with rising concentration of ions. Biomass as low as 0.8 g l−1 could biosorb 95% Cr(VI) ions within 2,880 min from an aqueous solution of 400 mg l−1 Cr(VI) concentration. Optimum pH and temperature for Cr(VI) biosorption were 2.0 and 50°C, respectively. Kinetic studies
based on pseudo second order models like Sobkowsk and Czerwinski, Ritchie, Blanchard and Ho and Mckay rate expressions have
also been carried out. The nature of the possible cell–metal ion interactions was evaluated by FTIR, SEM and EDAX analysis. 相似文献
17.
Hexavalent chromium reduction and accumulation by Acinetobacter AB1 isolated from Fez tanneries effluents were tested. The effects of some environmental factors such as pH, temperature,
and exposure time on Cr(VI) reduction and resistance were investigated. We found that this strain was able to resist to concentrations
as high as 400 mg/l of Cr(VI). Moreover, pH 10 and the temperature 30°C constitute favourable conditions to the growth and
reduction of Acinetobacter AB1. Complete reduction of Cr(VI) was observed at low initial Cr(VI) concentrations of 50 mg/l after 72 h of incubation.
Furthermore, Transmission electron microscope (TEM) analysis showed morphological changes in AB1 strain due 48H exposure to
100 mg/l chromate concentration and revealed circular electron dense (dark black point) inclusion within the cell cytoplasm
suggesting chromium deposition within the cells. 相似文献
18.
Battaglia-Brunet F Foucher S Denamur A Ignatiadis I Michel C Morin D 《Journal of industrial microbiology & biotechnology》2002,28(3):154-159
The ability of sulfate-reducing bacteria (SRB) to reduce chromate, Cr(VI), was evaluated using fixed-film growth systems and
H2 as the electron source. A main objective of the experiment was to distinguish between direct enzymatic reduction and indirect
reduction by hydrogen sulfide, in order to subsequently verify and control the synergy of these two mechanisms. In batch experiments
with the sulfate-reducing consortium CH10 selected from a mining site, 50 mg l−1 Cr(VI) was reduced in 15 min in the presence of 500 mg l−1 hydrogen sulfide compared to 16 mg l−1 reduced in 1 h without hydrogen sulfide. Fixed films of a CH10 population and Desulfomicrobium norvegicum were fed-batch grown in a column bioreactor. After development of the biofilm, hydrogen sulfide was removed and the column
was fed continuously with a 13-mg l−1 Cr(VI) solution. Specific Cr(VI) reduction rates on pozzolana were close to 90 mg Cr(VI) h−1 per gram of protein. Exposure to Cr(VI) had a negative effect on the subsequent ability of CH10 to reduce sulfate, but the
inhibited bacteria remained viable. Journal of Industrial Microbiology & Biotechnology (2002) 28, 154–159 DOI: 10.1038/sj/jim/7000226
Received 20 September 2000/ Accepted in revised form 13 November 2001 相似文献
19.
Heavy-metal chromium [Cr(VI)] is a ubiquitous environmental pollutant. Comparing with chemical reduction, microbiological
reduction is considered to be a friendly and cheaper way to decrease the damage caused by chromate. A bacterial strain, CR-07,
which is resistant to and capable of reducing chromate was isolated from a mud sample of iron ore and identified as a Microbacterium sp. The bacterium had a high degree of tolerance to chromate, and could grow in LB medium containing 4.08 mM of K2Cr2O7. It also had a degree of resistance to other heavy metals, e.g. Cd2+, Pb2+, Zn2+, Cu2+, Co2+, Hg2+ and Ag+. The bacterium could remove 1.02 mM of Cr(VI) from LB medium within 36 h of incubation. Chromate removal was achieved in
the supernatant from the bacterial cultures, and corresponded to chromate reduction. The activity of chromate reduction by
the bacterium was not related to enzymes or reducing sugars, while fluorometric assay suggested that glutathione, a chromate-reducing
substance which was produced by the bacterium, was one of the factors that contributed to the reduction of Cr(VI). 相似文献
20.
Andreazza R Okeke BC Pieniz S Brandelli A Lambais MR Camargo FA 《Biological trace element research》2011,143(2):1182-1192
Environmental copper contamination is a serious human health problem. Copper reductase is produced by microorganisms to facilitate
copper uptake by ATPases into the cells increasing copper biosorption. This study assessed the reduction of Cu(II) by cell-free
extracts of a highly copper-resistant bacterium, Pseudomonas sp. strain NA, isolated from vineyard soil contaminated with copper. Both intact cells and cell-free extract of Pseudomonas sp. strain NA displayed substantial reduction of Cu(II). Intact cells reduced more then 80 mg L−1 of Cu(II) from medium amended with 200 mg L−1 of copper after 24 h of incubation. Cell-free extract of the isolate reduced more than 65% of the Cu(II) at initial copper
concentration of 200 mg L−1 after 24 h. Soluble protein production was high at 72 h of incubation at 100 mg L−1 of copper, with more then 60 μg L−1 of total soluble protein in cell-free extract recorded. Cu(II) reduction by isolate NA was increased when copper concentration
increased for both intact cells and cell-free extract. Results indicate that Pseudomonas sp. strain NA produces copper reductase enzyme as the key mechanism of copper biotransformation. 相似文献