Cadmium biosorption by polyvinyl alcohol immobilized recombinant Escherichia coli

Cd immobilization mechanisms in a Pseudomonas strain and its application in soil Cd remediation

In this study, we isolated a highly cadmium (Cd)-resistant bacterium, Pseudomonas sp. B7, which immobilized 100% Cd(II) from medium. Culturing strain B7 with Cd(II) led to the change of functional groups, mediating extracellular Cd(II) adsorption. Proteomics showed that a carbonic anhydrase, CadW, was upregulated with Cd(II). CadW expression in Escherichia coli conferred resistance to Cd(II) and increased intracellular Cd(II) accumulation. Fluorescence assays demonstrated that CadW binds Cd(II) and the His123 residue affected Cd(II) binding activity, indicating that CadW participates in intracellular Cd(II) sequestration. Chinese cabbage pot experiments were performed using strain B7 and silicate [Si(IV)]. Compared with the control, Cd content in aboveground parts significantly decreased by 21.3%, 29.4% and 32.9%, and nonbioavailable Cd in soil significantly increased by 129.4%, 45.0% and 148.7% in B7, Si(IV) and B7 +Si(IV) treatments, respectively. The application of Si(IV) alone reduced chlorophyll content by 20.8% and arylsulfatase activity in soil by 33.9%, and increased malonaldehyde activity by 15.0%. The application of strain B7 alleviated the negative effect of Si(IV) on plant and soil enzymes. Overall, application of Si(IV) is most conducive to the decreased Cd accumulation in plant, and strain B7 is beneficial to maintaining soil and plant health.

Retained Negative Pressure Wound Therapy Foams as a Cause of Infection Persistence

Significance: Negative pressure wound therapy (NPWT) has become a valuable adjunct in the treatment of acute and chronic wounds in several surgical disciplines. Retained foams are among its side effects, and they pose a rare but devastating complication at the site of this therapy, which might be associated with wound-healing complications, infection persistence, repeated surgical revisions, and prolonged antibiotic courses. Recent Advances: In the past 15 years, an increasing number of studies have identified this potential problem. Although the exact incidence remains unknown, initial studies have indicated rates of up to 10% in large collectives being treated by NPWT. Critical Issues: The lack of radiopaque markers does not allow for the visual control of retained foams using plain radiographs. Further imaging methods (e.g., CT and MRI) also do not help in adequate differential diagnosis. The lack of routine documentation of the number, type, and localization of the inserted foam(s) and unplanned surgery with a different surgical team pose risk factors for foam retainment. Future Directions: Introducing new documentation records for wounds treated with NPWT is recommended. At foam removal, all dressing materials should be examined for integrity. The development of foams with radiopaque markers by the industry, such as those routinely used in surgical gauze swabs, might also be a useful step to minimize the risk of foam retainment within wounds.

Microbial Cd(II) and Cr(VI) resistance mechanisms and application in bioremediation

The heavy metals cadmium (Cd) and chromium (Cr) are extensively used in industry and result in water and soil contamination. The highly toxic Cd(II) and Cr(VI) are the most common soluble forms of Cd and Cr, respectively. They enter the human body through the food chain and drinking water and then cause serious illnesses. Microorganisms can adsorb metals or transform Cd(II) and Cr(VI) into insoluble or less bioavailable forms, and such strategies are applicable in Cd and Cr bioremediation. This review focuses on the highlighting of novel achievements on microbial Cd(II) and Cr(VI) resistance mechanisms and their bioremediation applications. In addition, the knowledge gaps and research perspectives are also discussed in order to build a bridge between the theoretical breakthrough and the resolution of Cd(II) and Cr(VI) contamination problems.

Assessment of cadmium tolerance and biosorptive potential of Bacillus Cereus GCFSD01 isolated from cadmium contaminated soil

Continuous occurrence of heavy metals is a major cause of environmental pollution due to its toxic effects. At minimum concentrations, these metals are highly reactive and can gather in the food chains and food web, causing major dangers to public health concerns. Soil samples were collected from Paharang drain, Faisalabad. Cadmium tolerant bacteria were isolated and evaluated for their MIC against Cd. The isolated bacterial strain GCFSD01 showed MIC value upto 30 mM/L. The bacterial strain with the highest resistance against Cd was selected for further study. Molecular characterization of bacterial isolate GCFSD01 was performed by 16S rRNA which confirmed it as Bacillus cereus. Optimum growth conditions of bacterial strain were also evaluated. Strain GCFSD01 showed optimum growth at pH 7 and 37 °C temperature. Our result revealed that B. cereus strain GCFSD01 reduced 61.3% Cd after 48 hrs. Multiple metal tolerance and Cd reduction by B. cereus indicate its potential for further use for decontamination of polluted soil.

The improved methods of heavy metals removal by biosorbents: A review

For decades, a vast array of innovative biosorbents have been found out and used in the removal of heavy metals, including bacteria, algae and fungi, etc. Although extensive biological species have been tried as a biosorbent for heavy metals removal, for removal efficiency or economy efficiency limited, it has failed to make a substantial breakthrough in practical application. Thus, many improved methods based on biosorbents emerged. In this review, based on the literature and our research results, we highlight three types of novel methods for biosorbents removal of heavy metals: chemical modification of biosorbents; biomass and chemical materials combination; multiple biomass complex systems. We mainly focus on their configuration, biosorption performance, their creation method, regeneration/reuse, their application and development in the future. Through the comparative analysis of various methods, we think that intracellular autogenous nanomaterials may open up another window in biosorption of heavy metals area. At the same time, the combination of various treatment methods will be the development tendency of heavy metal pollution treatment in the future.

Biosorption of dysprosium (III) using raw and surface-modified bark powder of Mangifera indica: isotherm, kinetic and thermodynamic studies

In this paper, we have used HDTMA-Br- and NaOH-treated bark powder of Mangifera indica as bio-sorbents for the removal of dysprosium (III) from its aqueous solution. The adsorption process was investigated at different experimental parameters such as contact time, temperature, pH, adsorbent dose, and initial metal concentration. The amount of chemically modified bark powder required was almost two times lesser than raw bark to get a higher percentage removal of the metal ion. The kinetics results revealed the adsorption process follows the nonlinear form a pseudo-second-order model. The negative values of Gibbs free energy change (∆G°) indicated the spontaneity of the adsorption process. The enthalpy change (∆H°) and entropy change (∆S°) of adsorption were 60.97 kJ/mol and 0.48 J/mol K, respectively signified it as an endothermic process. The maximum adsorption capacity was found to be 55.04 mg/g for sorption of Dy (III) on NaOH-treated bark powder and was better fitted to Langmuier model. It was confirmed to follow physisorption process and the activation energy of the system was found to be 41.07 kJ/mol. The possibility of adsorbent and adsorbate interactions were indicated by the FTIR and SEM/EDX analysis.

Novel magnetically separable anhydride-functionalized Fe3O4@SiO2@PEI-NTDA nanoparticles as effective adsorbents: synthesis, stability and recyclable adsorption performance for heavy metal ions

In this paper, a novel adsorbent, Fe₃O₄@SiO₂@PEI-NTDA, was first prepared by the immobilization of an amine and anhydride onto magnetic Fe₃O₄@SiO₂ nanoparticles with polyethylenimine (PEI) and 1,4,5,8-naphthalenetetracarboxylic-dianhydride (NTDA) for the removal of heavy metal ions from aqueous solutions. The structure of Fe₃O₄@SiO₂@PEI-NTDA was systematically investigated; the results confirmed that amine and anhydride groups were successfully covalently grafted onto the surface of Fe₃O₄@SiO₂, which showed a homogenous core–shell structure with three layers of about 300 nm diameter (Fe₃O₄ core: 200 nm, nSiO₂ layer: 20 nm, and PEI-NTDA layer: 20 nm). The adsorption performance of Fe₃O₄@SiO₂@PEI-NTDA NPs was evaluated for single Pb²⁺ and coexisting Cd²⁺, Ni²⁺, Cu²⁺, and Zn²⁺ ions in an aqueous solution in a batch system. The amine and anhydride groups may have a synergistic effect on Pb²⁺ removal through electrostatic interactions and chelation; Fe₃O₄@SiO₂@PEI-NTDA NPs exhibited preferable removal of Pb²⁺ with maximum adsorption capacity of 285.3 mg g⁻¹ for Pb²⁺ at a solution pH of 6.0, adsorbent dosage of 0.5 g L⁻¹, initial Pb²⁺ concentration of 200 mg L⁻¹ and contact time of 3 h. The adsorption mechanism conformed well to the Langmuir isotherm model, and the adsorption kinetic data were found to fit the pseudo-second order model. Fe₃O₄@SiO₂@PEI-NTDA NPs could be recovered easily from their dispersion by an external magnetic field and demonstrated good recyclability and reusability for at least 6 cycles with a high adsorption capacity above 204.5 mg g⁻¹. The magnetic adsorbents showed high stability with a weight loss below 0.65% in the acid leaching treatment by 2 M HCl solution for 144 h. This study indicates that Fe₃O₄@SiO₂@PEI-NTDA NPs are new promising adsorbents for the effective removal of Pb²⁺ in wastewater treatment.

A magnetically separable adsorbent, anhydride-functionalized Fe₃O₄@SiO₂@PEI-NTDA, was successfully constructed for removal of heavy metal ions from aqueous solution.

Evaluation of a novel chitosan polymer-based adsorbent for the removal of chromium (III) in aqueous solutions

Novel poly(vinyl alcohol)/citric acid/chitosan (PVA/CA/CHT, PCC) beads were prepared as an adsorbent for the removal of trivalent chromium (Cr(3+)) in aqueous solutions. PCC beads with different mass ratios (I, II, III, IV, V, ad VI) between PVA/CA/CHT were evaluated for the removal of Cr(3+) ions to find an optimal stoichiometry of PCC beads, which indicated that the PCC bead (II) with the PVA/CA/CHT mass ratio of 1/5/1 showed the highest adsorption for Cr(3+) ions. The surface characteristics of PCC beads (II) were determined by scanning electron microscopy using a field emission scanning electron microscope (FESEM) and Fourier transform infrared spectroscopy (FTIR). The results obtained in this study implied that PCC bead (II) had an obviously rough and folded structure, and its spectrum manifested significant changes compared to those of PVA, CA and CHT. The sorption experiments were conducted to evaluate the performance of PCC beads (II) to adsorb Cr(3+) ions in aqueous solutions. Results indicated that the Cr(3+) ion sorption onto PCC beads (II) was highly pH-dependent with the maximum uptake at pH 6.0. The sorption kinetics data were well fitted by the pseudo-second-order equation with high regression coefficients. Sorption isotherm of PCC beads (II) was well described by Langmuir equation, with a maximum sorption at 41.5mg Cr/g PCC beads (II). Desorption studies were also carried out by the repeated sorption/desorption experiments. The high efficiency and reusability of PCC beads (II) make them an attractive sorbent for the removal of Cr(3+) and possibly other metals in aqueous solutions.