Isolation, Molecular, and Metabolic Profiling of Benzene-Remediating Bacteria Inhabiting the Tannery Industry Soil

Benzene is a pervasive contaminant and human carcinogen. Its remediation from environmental resources using conventional procedures has always been challenging due to high cost and incomplete benzene degradation. The present study was designed to explore highly efficient bacteria with benzene degrading potential from tannery industry soil, which might be used as an alternative to these conventional benzene removal remedies. Bacterial isolation was performed using benzene (80 μl/1,000 ml) supplemented with minimal salt media (MSM). Characterization of isolates was carried out by performing growth curve analysis, Gram staining, biochemical characterization via Remel RapID™ NF PLUS System (Thermo Scientific™, Thermo Fisher Scientific, Inc., USA), antibiotic sensitivity profiling, 16S rRNA gene sequencing, benzene removal efficiency estimation assay, FTIR, and GC-MS profiling. Five bacteria isolated in the present study were identified as Paracoccus aestuarii PUB1, Bacillus tropicus PUB2, Bacillus albus PUB3, Bacillus subtilis PUB4, and Bacillus cereus PUB6. All of these fast-growing bacteria were Gram-positive except P. aestuarii PUB1. Maximum benzene removal efficiency (30 mg/l per 25 h) was found in B. tropicus PUB2. Comparing the FTIR spectra of bacterial culture supernatant versus control revealed the peaks shifting corresponding to benzene ring bonds breaking. GC-MS analysis identified the metabolic intermediates from benzoate methylation and benzaldehyde pathways. These bacteria can be employed for benzene degradation via enzyme-based nanoparticle synthesis or cloning of relevant genes in eco-friendly expression systems.

Biocompatible Osmium Telluride-Polypyrrole Nanocomposite Material: Application in Prostate Specific Antigen Immunosensing

Prostate cancer is a dominant global threat to society. It affects nearly 4000 men in South Africa annually, making it the second most threatening cancerous disease after lung cancer. A potential serological biomarker to monitor early diagnosis of prostate cancer is prostate specific antigen (PSA). We used the PSA biomarker in our work to develop an extremely sensitive electrochemical immunosensor to achieve low detection limits. The fabrication steps followed with the combination of thioglycolic acid capped osmium telluride quantum dots (TGA-OsTe2QD)-polypyrrole (PPy) nanocomposite and prostate specific antigen modified on a glassy carbon electrode. The UV-Vis signatures of TGA-OsTe2QD-PPy showed an absorption band at 262 nm which is attributed to the PPy and TGA-OsTe2QD composite. This band corresponds to the energy band gap of 4.4 and 5.4 eV. The CV responses of BSA|Ab|TGA-OsTe2QD|PPy|GCE modified electrode to prostate specific antigen (PSA) was studied within a range of 0–16 ng/mL PSA that was linear, herein referred to as liner range (LR), which produced a limit of detection (LOD) value of 0.36 ng/mL PSA. The values of the immunosensor’s calibration parameters (LR and LOD) make them suitable for real sample application, due to their coverage of the PSA concentration range (0–14 ng/mL) that is of clinical importance.

DNA-based low resistance palladium nano-spheres for effective hydrogen evolution reaction

Highly stable and less resistance Pd/DNA NSs are designed for HER in acidic medium and require a low overpotential (η10) of 79 mV. DNA plays multiple roles such as stabilizer, structure-directing agent and binder in the fabrication of electrodes.

An overview of palladium supported on carbon-based materials: Synthesis, characterization, and its catalytic activity for reduction of hexavalent chromium

Palladium plays a pivotal role in most of the industrial heterogeneous catalysts, because of its unique properties such as well-defined structure, great intrinsic carrier, outstanding electronic, mechanical and thermal stability. The combination of palladium and various porous carbons (PCs) can widen the use of heterogeneous catalysts. This review highlights the advantages and limitations of carbon supported palladium-based heterogeneous catalyst in reduction of toxic hexavalent chromium (Cr^(VI)). In addition, we address recent progress on synthesis routes for mono and bimetallic palladium nanoparticles supported by various carbon composites including graphene-based materials, carbon nanotubes, mesoporous carbons, and activated carbons. The related reaction mechanisms for the Cr^(VI) reduction are also suggested. Finally, the challenge and perspective are proposed.

Ligand's electronegativity controls the sense of enantioselectivity in BIFOP-X palladium-catalyzed allylic alkylations

Palladium-catalyzed allylic alkylations of Na(CH(CO₂Me)₂ with 1,3-diphenylallyl acetate, employing BIFOP-X (X = H, D, Cl, CN, N3) ligands, yield the C–C coupling product (up to 91% yield, 70% ee). A NBO effect reveals a change of stereochemistry.

Unprotected and interconnected Ru0 nano-chain networks: advantages of unprotected surfaces in catalysis and electrocatalysis

Seedless, surfactantless and support-free unprotected, metallic, interconnected nano-chain networks of ruthenium nanoparticles (NPs) were successfully synthesized via the reduction of ruthenium(iii) chloride (RuCl3) with sodium borohydride (NaBH4) at three different temperatures, viz. 30 °C, 45 °C and 60 °C. The molar ratio of RuCl3 solution and borohydride was optimized to be 1 : 1.5 to produce stable colloids with the optimum final solution pH of 9.7 ± 0.2. Average diameters of the interconnected nano-chain networks prepared at 30 °C (Ru-30), 45 °C (Ru-45) and 60 °C (Ru-60) were 3.5 ± 0.5 nm, 3.0 ± 0.2 nm and 2.6 ± 0.2 nm respectively. The morphology and composition dependent catalytic and electrocatalytic activities of these unprotected Ru nano-chain networks (Ru-30, Ru-45 and Ru-60) were studied in detail. The catalysis study was performed by investigating the transfer hydrogenation of several substituted aromatic nitro compounds. It was observed that Ru-60 was relatively more active compared to Ru-30 and Ru-45, which was reflected in their rate constant values. The electrocatalytic activities of Ru-30, Ru-45 and Ru-60 were screened for anodic water splitting in alkaline medium (0.1 M NaOH) and it was found that all of them showed almost the same activity which required an over-voltage of 308 ± 2 mV to obtain an anodic current density of 10 mA cm-2. The catalytic and electrocatalytic performances of these unprotected Ru0 networks were compared with Ru0 nanomaterials prepared under similar conditions with three different surfactants, viz. CTAB, SDS and TX-100, which revealed that unprotected Ru0 networks are better catalysts than those stabilized with surfactants. The superior catalytic and electrocatalytic performance is due to the availability of unprotected Ru0 surfaces. The present route may provide a new possibility of synthesizing other surfactant-free, unprotected metal colloids for enhanced catalytic and electrocatalytic applications.