Bioremediation Of Hexavalent Chromium Research Articles

Bioremediation of Hexavalent Chromium (Cr6+) by Active Cell Serratia odorifera TIU10 (STIU10) That Improves Growth and Reduces Bioaccumulation Factor of Vigna radiata L. in Chromium Contaminated Soil

Bioremediation of Hexavalent Chromium (Cr6+) by Active Cell Serratia odorifera TIU10 (STIU10) That Improves Growth and Reduces Bioaccumulation Factor of Vigna radiata L. in Chromium Contaminated Soil

Bioremediation of Hexavalent Chromium By Bacteria Isolated From Buriganga River, Dhaka City

Environmental pollution due to hexavalent chromium (Cr6+) is widespread because of the anthropogenic activities in various industrial processes, notably in leather tanning. Hexavalent chromium (Cr6+) is considered as highly toxic, carcinogenic, and mutagenic due to its high solubility in water, interaction with cellular proteins, and biological membrane permeability. Trivalent chromium (Cr3+), on the other hand, is less water-soluble, and relatively benign in nature. Thus, bioreduction of toxic Cr6+ to relatively non-toxic Cr3+ by microorganisms can be an inexpensive and eco-friendly option for chromium bioremediation. In this regard, the present study attempted to isolate chromium-reducing bacteria from Buriganga River in order to assess their capability for chromium bioremediation. Ten chromium-tolerating bacterial isolates were successfully identified. The results revealed that these isolates, particularly strains of Bacillus subtilis, exhibited a remarkable ability to remove up to 89% of hexavalent chromium from the contaminated medium within three days of incubation.
 Stamford Journal of Microbiology, 2023. Vol. 13, Issue 1, p. 25-29

Chromium, its properties, transformation, and impact on humans

This review presents current views on the features of сhromium and its compounds, their interconversion, reduction of Cr (VI) by microorganisms, as well as the impact of chromium (VI) on the environment and humans. Chromium can have positive and negative effects on health, according to the dose, exposure time, and oxidation state. The most common forms of this metal in biological systems are trivalent Cr(III) and hexavalent Cr(VI). Hexavalent chromium is mobile, highly toxic to humans, and animals and considered a priority environmental pollutant. He is highly soluble and mobile. On the contrary, Cr(III) has relatively low toxicity and mobility and it is one of the micronutrients needed by humans. Сhromium (III) is an essential nutrient required to promote the action of insulin in body tissues so that the body can use sugars, proteins, and fats. Considerable attention is paid to the issues of interconversion of chromium compounds, reduction of Cr (VI) to Cr (III) by microorganisms, as well as physiological features of their action in humans. The present review discusses on the types of chromate reductases found in different bacteria, their mode of action, and potential applications in the bioremediation of hexavalent chromium. Іn the human body chromium (VI) is rapidly reduced to chromium (III) after penetration of biological membranes and in the gastric environment. The reduction of Cr(VI) to Cr(III) results in the formation of reactive intermediates that together with stress oxidative tissue damage and a cascade of cellular events, contribute to the cytotoxicity, genotoxicity, and carcinogenicity of Cr(VI)-containing compounds.

Purification and Characterization of Extracellular Cr(VI) Reductase from Bacillus amyloliquefaciens (CSB 9) isolated from Chromite Mine Soil for Detoxification of Hexavalent Chromium

Chromate is widely used industrial pollutant which can be detoxified effectively using chromate reductase from chromium resistant bacteria. A soluble Cr(VI) reductase from Bacillus amyloliquefaciens (CSB 9) was extracted and purified to electrophoretic homogeneity through (NH4)2SO4 precipitation followed by dialysis and gel filtration chromatography with specific activity of 0.167 U/mg and 6% yield with 30.36-fold increase in purity. Based on sodium dodecyl sulfate-polyacrylamide gel electrophoresis, the molecular weight of the purified enzyme was estimated to be ~ 116 KDa. Further, functional characterization with respect to pH, temperature and storage stability showed optimum Cr(VI) activity at 35 °C and pH 7.0 on standard analysis conditions. Using potassium dichromate as substrate, the enzyme kinetics showed maximum activity (Vmax) of 3.5 U/mL with its corresponding KM value of 27.78 μM and the second-order constant (Vmax/Km) 0.125 U/μM mL. The purified enzyme exhibited higher stability (μM/mg/min) when treated with additives such as metal ions K+ (1.3 ± 0.056), surfactant tween 80 (2.33 ± 0.52), inhibitor β-mercaptoethanol (0.67 ± 0.15) and organic solvent glycerol (1.33 ± 0.011). These remarkable qualities found with the chromate reductase produced by B. amyloliquefaciens (CSB 9) could make it an ideal candidate for bioremediation of hexavalent chromium under a wide range of environmental conditions.

Bioremediation of hexavalent chromium by an indigenous bacterium Bacillus cereus S10C1: optimization study using two level full factorial experimental design

Bioremediation of hexavalent chromium by an indigenous bacterium Bacillus cereus S10C1: optimization study using two level full factorial experimental design

Bioremediation of hexavalent chromium from wastewater using bacteria-a green technology.

Hexavalent chromium has high toxic effect on the ecological system. The aim of the present study is to isolate and characterize the bacteria that can reduce the toxicity of hexavalent chromium from liquid effluent. The bacterial isolate was identified as Bacillus sp. ltds1 after 16S rRNA gene sequencing, and annotation has been submitted in National Center for Biotechnology Information (NCBI) GenBank. The bacterial strain was found able to grow in Luria Broth medium at 100mg/L Cr6+ concentration. A maximum Cr6+ bioremediation (95.24 ± 2.08 %) could be achieved using the said isolate at 40mg/L, pH 7, and inoculum concentration 4 % at 24h. The residual chromium was found in the form of less toxic trivalent chromium (Cr3+), which confirms that the bacterial isolate can transform toxic Cr6+ to non-toxic Cr3+. Fourier Transform Infra-Red (FTIR) study was performed to analyze the functional groups and overall nature of chemical bonds involved in the remediation process, whereas, Energy-Dispersive Spectroscopy (EDS) studies of native and treated cells showed the changes in elemental composition in response to metal stress. Artificial Neural Network (ANN) based prediction model is developed based on experimental points. The developed model was found to predict the bioremediation of Cr6+ at various operating conditions. Particle Swarm Optimization (PSO) is used to optimize the variables like the initial concentration of metal, pH, temperature, and inoculum concentration for the said bacterial strain. The results showed that the isolate could be applied as a potential bioremediation agent for Cr6+ removal.

Bioremediation of Hexavalent Chromium by Chromium Resistant Bacteria Reduces Phytotoxicity.

Chromium (Cr) (VI) has long been known as an environmental hazard that can be reduced from aqueous solutions through bioremediation by living cells. In this study, we investigated the efficiency of reduction and biosorption of Cr(VI) by chromate resistant bacteria isolated from tannery effluent. From 28 screened Cr(VI) resistant isolates, selected bacterial strain SH-1 was identified as Klebsiella sp. via 16S rRNA sequencing. In Luria–Bertani broth, the relative reduction level of Cr(VI) was 95%, but in tannery effluent, it was 63.08% after 72 h of incubation. The cell-free extract of SH-1 showed a 72.2% reduction of Cr(VI), which indicated a higher activity of Cr(VI) reducing enzyme than the control. Live and dead biomass of SH-1 adsorbed 51.25 mg and 29.03 mg Cr(VI) per gram of dry weight, respectively. Two adsorption isotherm models—Langmuir and Freundlich—were used for the illustration of Cr(VI) biosorption using SH-1 live biomass. Scanning electron microscopy (SEM) analysis showed an increased cell size of the treated biomass when compared to the controlled biomass, which supports the adsorption of reduced Cr on the biomass cell surface. Fourier-transform infrared analysis indicated that Cr(VI) had an effect on bacterial biomass, including quantitative and structural modifications. Moreover, the chickpea seed germination study showed beneficial environmental effects that suggest possible application of the isolate for the bioremediation of toxic Cr(VI).

Bioremediation of hexavalent chromium by endophytic fungi; safe and improved production of Lactuca sativa L

One of the main problems of the industrialized world is the accumulation of chromium (Cr) in soil, which is a serious threat to the crops. Complete removal of Cr from the contaminated soils poses a great challenge. However, this issue can be minimised by using plant growth promoting microbes as a bioremediation tool. In the present study, healthy plants established near the University campus in Mardan were selected for the isolation of Cr resistant endophytes. From the designated plants, 114 species of endophytic fungi were isolated. Among the 114 isolated strains, 4 strains have induced resistance in L. sativa against Cr. The strains were identified as Aspergillus fumigatus, Rhizopus sp., Penicillium radicum and Fusarium proliferatum based on ITS region (18 S rDNA) homology. The isolates have removed Cr from soil and culture media as well as bio-transformed it from highly toxic hexavalent to least toxic trivalent form, thus helped the Cr stressed L. sativa to restore its normal growth. The Rhizopus Sp. CUC23 has mainly accrued Cr and detoxified intracellularly, whereas A. fumigatus ML43 and P. radicum PL17 has detoxified up to 95% of Cr extracellularly. From the results, it is concluded that the selected endophytic strains might be used as biofertilizer for healthy and safe crop production in Cr contaminated soils.

Bacillus sp. G3 un microorganismo promisorio en la biorremediación de aguas industriales contaminadas con cromo hexavalente

Introducción: El presente trabajo tuvo como objetivo buscar y caracterizar microorganismos provenientes de un agua residual industrial promisorios en biorremediación de aguas contaminadas con cromo hexavalente.Metodología: Se realizó el aislamiento de tres microorganismos partiendo de un agua residual industrial proveniente de una empresa de galvanoplastia. Se evaluó el potencial de los microorganismos aislados en su capacidad para reducir cromo hexavalente; escogiéndose al aislado bacteriano G3 por mostrase promisorio en biorremediación de cromo hexavalente. Se realizó la caracterización del aislado seleccionado y se evaluó el potencial de reducción de cromo hexavalente asociado a la actividad biológica y la actividad enzimática utilizando un extracto libre de células; de forma adicional, se realizaron bioensayos de reducción de cromo evaluando la acción conjunta de los 3 microorganismos.Resultados: Los datos moleculares y pruebas bioquímicas sugieren que el asilado bacteriano G3 pertenece al género Bacillus mostrado cercanía con las especies de Bacillus cereus y Bacillus thuringiensis. Los bioensayos de reducción de cromo hexavalente (10 mg/L) realizados con Bacillus sp. G3 mostraron una reducción del 100% del contaminante al cabo de diez horas en medio LB y de 34 horas en agua residual industrial. El extracto libre de células obtenido a partir del aislado bacteriano G3 mostró actividad de cromato reductasa con valores óptimos de actividad relativa a una temperatura de 28ºC y 6,5 de pH. La acción conjunta de los microorganismos sobre la reducción de cromo se mostró cinco veces menos eficiente que los ensayos realizados solo con la cepa G3.Discusión o conclusión: Los resultados sugieren, que el aislado bacteriano G3 se muestra como un microorganismo con buen potencial para ser utilizado en procesos de biorremediación de aguas contaminadas con cromo hexavalente, en particular para la descontaminación de aguas industriales.

Bioremediation of Hexavalent Chromium in Potassium Dichromate Solution by Botrytis aclada fres and Chrysonilia sitophila

Bioremediation of hexavalent chromium, Cr(VI) by Botrytis aclada fres and Chrysonilia sitophila was studied. The organisms were isolated from decaying onion bulb and apple fruit respectively, purified in Potato Dextrose Agar, and grown for 144 hours in solutions of potassium dichromate of concentrations ranging from 5-20 mg/l at 40 0 C. Effective reduction of Cr(VI) was observed at 5-20 mg/l compared to 25 mg/l dichromate treatments in both organisms. The results showed significant decrease (P < 0.05) in biomass concentration in the two fungi used with increasing concentration of the dichromate treatment (5-25 mg/l). Significant increase (P < 0.05) in residual glucose concentration was also observed in the culture media with increase in concentration of the dichromate treatment. However, at 20 mg/l dichromate treatment, Cr(IV) concentration, 1.36 ± 0.02 and 1.71 ± 0.03 (P < 0.05) were revealed in the culture media of B. aclada fres and C. sitophila respectively. Also, 0.71 ± 0.03 and 0.94 ± 0.03 Cr(IV) concentration (P < 0.05) were observed in the fungal mycelia at 20 mg/l dichromate treatment in B. aclada fres and C. sitophila respectively. After 144 hours of growth, Cr(VI) reduction of 89.65% in B. aclada fres and 86.75% in C. sitophila at 20 mg/l dichromate treatment were revealed. This investigation suggests that the two fungi adopted a process of reduction to tolerate the toxicity of hexavalent chromium. The results indicate the potentials of the fungi in bioremediation particularly in the treatment of waste water containing hexavalent chromium.

Bioremediation of hexavalent and trivalent chromium using Citrobacter freundii: a mechanistic study

The mechanisms involved in the bioremediation of hexavalent chromium (Cr(VI)) and trivalent chromium (Cr(III)) by a Gram negative bacterium, Citrobacter freundii were independently investigated. The biosorption isotherms of Cr(VI) and Cr(III) for C. freundii exhibited a typical Langmuirian behaviour. The Gibbs free energy (ΔG) was determined to be -25.5 and −27.2 kJ mol−1, respectively for Cr(VI) and Cr(III), suggestive of chemisorption between the functional groups of bacterial surface and Cr. The relatively lesser amount of desorption of Cr(VI) or Cr(III) from the bacterial cells attested to the irreversible nature of biosorption. FTIR studies revealed the involvement of carboxyl, amino and hydroxyl groups in the biosorption of Cr(VI) and Cr(III). X-ray photoelectron spectroscopic studies provided evidence in support of the bioreduction from Cr(VI) to Cr(III). Electrokinetic studies revealed that the bacterial cells become less electronegative after interaction with Cr species. The mechanisms of bioremediation have been delineated to involve both biosorption and bioreduction processes for Cr(VI), while for Cr(III), biosorption is the governing process of remediation.

Bioremediation of Hexavalent Chromium by Some Marine Algae

Bioremediation of Hexavalent Chromium by Some Marine Algae

Bioremediation of hexavalent chromium (VI) by a soil-borne bacterium, Enterobacter cloacae B2-DHA

Chromium and chromium containing compounds are discharged into the nature as waste from anthropogenic activities, such as industries, agriculture, forest farming, mining and metallurgy. Continued disposal of these compounds to the environment leads to development of various lethal diseases in both humans and animals. In this paper, we report a soil borne bacterium, B2-DHA that can be used as a vehicle to effectively remove chromium from the contaminated sources. B2-DHA is resistant to chromium with a MIC value of 1000 µg mL−1 potassium chromate. The bacterium has been identified as a Gram negative, Enterobacter cloacae based on biochemical characteristics and 16S rRNA gene analysis. TOF-SIMS and ICP-MS analyses confirmed intracellular accumulation of chromium and thus its removal from the contaminated liquid medium. Chromium accumulation in cells was 320 µg/g of cells dry biomass after 120-h exposure, and thus it reduced the chromium concentration in the liquid medium by as much as 81%. Environmental scanning electron micrograph revealed the effect of metals on cellular morphology of the isolates. Altogether, our results indicate that B2-DHA has the potential to reduce chromium significantly to safe levels from the contaminated environments and suggest the potential use of this bacterium in reducing human exposure to chromium, hence avoiding poisoning.

Genomic Analysis and Comparative Hexavalent Chromium Reduction Potential of Predominant Bacillus species Isolated from Chromite Mine Soil

Ten predominant bacteria (CSB 1-10), isolated from chromite mine soil of Sukinda, Odisha, were characterized by means of biochemical and 16S rRNA gene sequencing. All of the bacterial isolates were Gram-positive, spore-forming, and motile rods with diameter ranging from 1.57–2.79 μm and identified as Bacillus species. Based on 16S rRNA gene sequencing and phylogenetic tree construction, 10 Bacillus species were grouped into two clusters: Bacillus subtilis cluster with four species (two of B. amyloliquefaciens, and one each of B. tequilensis and B. mojavensis); and Bacillus cereus cluster containing six species of B. cereus. Secondary rRNA structure predicted for all 10 bacteria using 16S rRNA sequences revealed some degree of genetic variations among the species. Among the isolated bacteria, CSB-9 was found to be the most efficient chromate reducing strain (0.8 × 10−4 mg mg−1 h−1) in comparison to the others. Chromate reduction of the bacteria was associated with the contribution of extracellular enzyme production, and highest enzyme activity (0.9 ± 0.09 U mL−1) was observed in CSB-9 (B. amyloliquefaciens). The present study revealed the dominance of Bacillus species in the chromite mine soil and their potential for bioremediation of hexavalent chromium from the polluted environments.

Mechanism of Cr(VI) reduction by Aspergillus niger: enzymatic characteristic, oxidative stress response, and reduction product.

Bioremediation of hexavalent chromium by Aspergillus niger was attributed to the reduction product (trivalent chromium) that could be removed in precipitation and immobilized inside the fungal cells and on the surface of mycelium. The site location of reduction was conducted with assays of the permeabilized cells, cell-free extracts, and cell debris, which confirmed that the chromate reductase was mainly located in the soluble fraction of cells. The oxidation-reduction process was accompanied by the increase of reactive oxygen species and antioxidant levels after hexavalent chromium treatment. Michaelis-Menten constant (K(m)) and maximum reaction rate (V(max)), obtained from the Lineweaver-Burk plot were 14.68 μM and 434 μM min(-1) mg(-1) of protein, respectively. Scanning electron microscopy and Raman spectra analyses manifested that both Cr(VI) and Cr(III) species were present on the mycelium. Fourier transform-infrared spectroscopy analysis suggested that carboxyl, hydroxide, amine, amide, cyano-group, and phosphate groups from the fungal cell wall were involved in chromium binding by the complexation with the Cr(III) and Cr(VI) species. A Cr(VI) removal mechanism of Cr(VI) reduction followed by the surface immobilization and intracellular accumulation of Cr(III) in living A. niger was present.

Surfactant Assisted Enhancement of Bioremediation Rate for Hexavalent Chromium by Water Extract of Siris (Albizia lebbeck) Sawdust

Abstract Cr(VI) is introduced into environment as a byproduct of industries. It is highly toxic. Biosorption of hexavalent chromium by various types of sawdust appears as a very cost-effective alternative for decontamination of Cr(VI) bearing effluents. In this work water extract of siris sawdust is used for the bioremediation of hexavalent chromium. Cr(VI) ions were reduced to Cr(III) ions as a result of oxidation of organic components present in the water extract of siris sawdust. Formation of Cr(III) is proved by UV-VIS spectroscopy. Functional groups involved in the reduction of Cr(VI) are characterized by FTIR spectroscopy. Bioremediation rate is increased by the use of anionic surfactant sodium dodecylsulphate (SDS) and neutral surfactant Triton-X-100 (TX-100). Here they act as micellar catalyst. Formation of micelles which is responsible for the catalysis of the process is proved by SEM and optical images of the solution. In absence of surfactants 39 % of the total chromium(VI) is reduced within 531 h whereas removal percentage increases upto 54 % in presence of TX-100. Again in presence of SDS the reduction process is almost 99 % complete within 531 h.

Bioremediation of hexavalent chromium by a cyanobacterial mat

The study comprises the use of cyanobacterial mat (collected from tannery effluent site) to remove hexavalent chromium. This mat was consortium of cyanobacteria/blue-green algae such as Chlorella sp., Phormidium sp. and Oscillatoria sp. The adsorption experiments were carried out in batches using chromium concentrations 2–10, 15–30 and 300 ppm at pH 5.5–6.2. The adsorption started within 15 min; however, 96 % reduction in metal concentration was observed within 210 min. The adsorption phenomenon was confirmed by Fourier transform–infrared spectroscopy and energy dispersive X-ray analysis. This biosorption fitted Freundlich adsorption isotherm very well. It was observed that the best adsorption was at 4 ppm, and at 25 ppm in the chosen concentration ranges. Scanning electron micrograph showed the physiology of mat, indicating sites for metal uptake. The main focus was collection of the cyanobacterial mat from local environments and its chromium removal potential at pH 5.5–6.2.

Bioremediation of Cr(VI) from Chromium-Contaminated Wastewater by Free and Immobilized Cells of Cellulosimicrobium cellulans KUCr3

ABSTRACT In this report, possible utilization of a chromium-reducing bacterial strain Cellulosimicrobium cellulans KUCr3 for effective bioremediation of hexavalent chromium (Cr(VI))-containing wastewater fed with tannery effluents has been discussed. Cr(VI) reduction and bioremediation were found to be related to the growth supportive conditions in wastewater, which is indicative of cell mass dependency for Cr(VI) reduction. Cr(VI) reduction was determined by measuring the residual Cr(VI) in the cell-free supernatant using colorimetric reagent S-diphenylcarbazide. Nutrient availability and initial cell density showed a positive relation with Cr(VI) reduction, but it was inhibited with increasing concentration of Cr(VI) under laboratory condition. The optimum temperature and pH for effective Cr(VI) reduction in wastewater were found to be 35°C and 7.5, respectively. The viable cells of KUCr3 were successfully entrapped in an agarose bead that was used in continuous column and batch culture for assaying Cr(VI) reduction. In packed bed column (continuous flow) experiment, approximately 25% Cr(VI) reduction occurred after 144 h. Cr(VI) was almost 75% and 52% reduced at concentrations of 0.5 mM and 2 mM Cr(VI), respectively, after 96 h in batch culture experiment in peptone-yeast extract-glucose medium, whereas it could decrease the Cr(VI) content up to 40% from the water containing tannery waste. This study suggests that KUCr3 could be used as a candidate for possible environmental clean up operation with respect to Cr(VI) bioremediation.

Bioremediation of hexavalent chromium contaminated water in fixed-film upflow reactors - a south african first

Bioremediation of hexavalent chromium contaminated water in fixed-film upflow reactors - a south african first

Bioremediation of Hexavalent Chromium and Tannic Acid in Synthetic Tannery Wastewater Using Free and Calcium Alginate–Immobilized Spores and Mycelia of Aspergillus niger and Aspergillus parasiticus

ABSTRACT The bioremediation of chromate and tannic acid in synthetic tannery wastewater was studied in a batch culture system using free and immobilized spores and mycelia of A. niger and A. parasiticus. Significant (p< .001) decreases in total dissolved solids (TDS), biochemical oxygen demand (BOD), chemical oxygen demand (COD), Cr(VI), and tannic acid concentrations were observed in cultures of both fungi after 96 h of growth. The A. niger culture medium had significantly lower TDS (p< .001), BOD, and tannic acid concentration (p< .05) compared to that of A. parasiticus. Immobilization of both spores and mycelia of the two fungi on Ca-alginate resulted in significantly (p< .05–.001) lower residual Cr(VI) concentrations within 24 h hydraulic retention time (HRT). Chromate removal increased significantly (p< .05) as the number of beads of immobilized spore/mycelia increased from 10 to 100; the increase in Cr(VI) removal ranging from 40.3% to 47.9% with 10 beads and 97.4% to 98.6% with 100 beads. Similarly, tannic acid removal by spores and mycelia of the fungi was significantly (p< .05) enhanced by immobilization. Repeated use of the alginate entrapped spores/mycelia of both fungi up to 3 cycles of 72-h HRT showed no significant change in their ability to carryout Cr(VI) removal.