Computational detailsElectronic structure calculations based on density functional theory (DFT) [1] are carried out using accurate plane augmented wave (PAW) method [2] as implemented in Vienna Ab initio Simulations Package (VASP) [3]. The exchange-correlation energy functional as given by Perdew, Burke and Ernzerhof (PBE) [4] is used, since it is known to provide descent estimates for electronic properties. The valence electronic configurations used for Zn and S are 4s 2 3d 10
Dioscorea bulbiferais a potent medicinal plant used in both Indian and Chinese traditional medicine owing to its rich phytochemical diversity. Herein, we report the rapid synthesis of novelAucoreAgshellnanoparticles byD. bulbiferatuber extract (DBTE).AucoreAgshellNPs synthesis was completed within 5 h showing a prominent peak at 540 nm. HRTEM analysis revealed 9 nm inner core of elemental gold covered by a silver shell giving a total particle diameter upto 15 nm.AucoreAgshellNPs were comprised of57.34±1.01% gold and42.66±0.97% silver of the total mass.AucoreAgshellNPs showed highest biofilm inhibition upto83.68±0.09% againstA. baumannii. Biofilms ofP. aeruginosa,E. coli, andS. aureuswere inhibited up to18.93±1.94%,22.33±0.56%, and30.70±1.33%, respectively. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) confirmed unregulated cellular efflux through pore formation leading to cell death. Potent antileishmanial activity ofAucoreAgshellNPs (MIC=32 µg/mL) was confirmed by MTT assay. Further SEM micrographs showed pronounced deformity in the spindle shaped cellular morphology changing to spherical. This is the first report of synthesis, characterization, antibiofilm, and antileishmanial activity ofAucoreAgshellNPs synthesized byD. bulbifera.
Simultaneous removal of selenite and tellurite from synthetic wastewater was achieved through microbial reduction in a lab-scale upflow anaerobic sludge blanket reactor operated with 12 h hydraulic retention time at 30 °C and pH 7 for 120 days. Lactate was supplied as electron donor at an organic loading rate of 528 or 880 mg COD L day. The reactor was initially fed with a synthetic influent containing 0.05 mM selenite and tellurite each (phase I, day 1-60) and subsequently with 0.1 mM selenite and tellurite each (phase II, day 61-120). At the end of phase I, selenite and tellurite removal efficiencies were 93 and 96%, respectively. The removal percentage dropped to 87 and 81% for selenite and tellurite, respectively, at the beginning of phase II because of the increased influent concentrations. The removal efficiencies of both selenite and tellurite were gradually restored within 20 days and stabilized at ≥ 97% towards the end of the experiment. Powder X-ray diffraction and Raman spectroscopy confirmed the formation of biogenic Se(0), Te(0), and Se(0)-Te(0) nanostructures. Scanning transmission electron microscopy coupled with energy-dispersive X-ray spectroscopy showed aggregates comprising of Se(0), Te(0), and Se-Te nanostructures embedded in a layer of extracellular polymeric substances (EPS). Infrared spectroscopy confirmed the presence of chemical signatures of the EPS which capped the nanoparticle aggregates that had been formed and immobilized in the granular sludge. This study suggests a model for technologies for remediation of effluents containing Se and Te oxyanions coupled with biorecovery of bimetal(loid) nanostructures.
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