Antifungal Activity Enhancement of Cell-Free Streptomyces griseus Extract Obtained by Fermentation with Magnetic Manganese Ferrite Nanoparticles

The present study aims to obtain manganese ferrite nanoparticles functionalized with chitosan (C-MNP) or ethylenediamine (E-MNP) by coprecipitation and polyol one-step methods, characterize their interaction with S. griseus demonstrating cell immobilization, and evaluate the antimicrobial activity of the free cell extracts obtained from immobilized S. griseus fermentation in the presence of different concentrations of MNP. The adsorption isotherms were analyzed mathematically using Langmuir and Freundlich models. The highest coefficient of determination (R2) for the S. griseus cell adsorption isotherm with C-MNP was observed with a linear function of the Langmuir model. The adsorption isotherm of S. griseus cells with E-MNP was better fitted to the Freundlich model. Cell immobilization by adsorption on magnetic nanoparticles was demonstrated in both cases. Different concentrations of C-MNP and E-MNP were used in fermentations to prepare cell-free extracts with antifungal activity. The best results were obtained with E-MNP, with a 91.5% inhibition of radial fungal growth. Magnetic nanoparticles offer potential applications in different fields and easy biomass separation.

Enhanced Visible Light-Driven Photoelectrocatalytic Degradation of Paracetamol at a Ternary z-Scheme Heterojunction of Bi2WO6 with Carbon Nanoparticles and TiO2 Nanotube Arrays Electrode

In this study, a ternary z-scheme heterojunction of Bi₂WO₆ with carbon nanoparticles and TiO₂ nanotube arrays was used to remove paracetamol from water by photoelectrocatalysis. The materials and z-scheme electrode were characterised using X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), energy dispersive X-ray spectroscopy (EDS), EDS mapping, ultraviolet diffuse reflection spectroscopy (UV-DRS), photocurrent measurement, electrochemical impedance spectroscopy (EIS), uv-vis spectroscopy and total organic carbon measurement (TOC). The effect of parameters such as current density and pH were studied. At optimal conditions, the electrode was applied for photoelectrocatalytic degradation of paracetamol, which gave a degradation efficiency of 84% within 180 min. The total organic carbon removal percentage obtained when using this electrode was 72%. Scavenger studies revealed that the holes played a crucial role during the photoelectrocatalytic degradation of paracetamol. The electrode showed high stability and reusability therefore suggesting that the z-scheme Bi₂WO₆-CNP-TiO₂ nanotube arrays electrode is an efficient photoanode for the degradation of pharmaceuticals in wastewater.

Efficient removal of cadmium (II) ions from aqueous solution by CoFe2O4/chitosan and NiFe2O4/chitosan composites as adsorbents

Magnetically recoverable chitosan based spinel cobalt and nickel ferrite (CS/CoFe₂O₄ and CS/NiFe₂O₄, respectively) composites were successfully prepared in one step. A series of batch adsorption experiments indicated that the removal of toxic Cd(II) ions by the as-obtained composites as adsorbents was pH-dependent, rapid, proficient, better fitted to pseudo-second-order kinetics model and Langmuir monolayer adsorption isotherm model. Compared to the naked particles, magnetic bio-polymer composites exhibited promoted adsorption capacity. Competitive adsorption studies in binary solutions illustrated preferable selectivity of adsorbents toward Cd(II) ions in the presence of co-existing cations. More importantly, CS/CoFe₂O₄ and CS/NiFe₂O₄ had a satisfactory practical application in the removal of Cd(II) from real groundwater spiked with cadmium. The exhausted adsorbents could be regenerated efficiently by 0.5 M HNO₃. The results from this study support that CS/CoFe₂O₄ and CS/NiFe₂O₄ prove excellent adsorption behavior for the removal of Cd(II) ions from aqueous media.