Effect of biosynthesized silver nanoparticles on bacterial biofilm changes in S. aureus and E. coli.

One approach for solving the problem of antibiotic resistance and bacterial persistence in biofilms is treatment with metals, including silver in the form of silver nanoparticles (AgNPs). Green synthesis is an environmentally friendly method to synthesize nanoparticles with a broad spectrum of unique properties that depend on the plant extracts used. AgNPs with antibacterial and antibiofilm effects were obtained using green synthesis from plant extracts of Lagerstroemia indica (AgNPs_LI), Alstonia scholaris (AgNPs_AS), and Aglaonema multifolium (AgNPs_AM). Nanoparticles were characterized by transmission electron microscopy (TEM) and energy-dispersive X-ray spectroscopy (EDX) analysis. The ability to quench free radicals and total phenolic content in solution were also evaluated. The antibacterial activity of AgNPs was studied by growth curves as well as using a diffusion test on agar medium plates to determine minimal inhibitory concentrations (MICs). The effect of AgNPs on bacterial biofilms was evaluated by crystal violet (CV) staining. Average minimum inhibitory concentrations of AgNPs_LI, AgNPs_AS, AgNPs_AM were 15 ± 5, 20 + 5, 20 + 5 μg/mL and 20 ± 5, 15 + 5, 15 + 5 μg/mL against Gram-positive (Staphylococcus aureus) and Gram-negative (Escherichia coli) bacteria, respectively. The E. coli strain formed biofilms in the presence of AgNPs, a less dense biofilm than the S. aureus strain. The highest inhibitory and destructive effect on biofilms was exhibited by AgNPs prepared using an extract from L. indica

Surfactant-modified Macadamia nutshell for enhancement of methylene blue dye adsorption from aqueous media

This study reported the synthesis of a low-cost, and efficient adsorbent through surfactant modified macadamia nutshells (SMS) by a facile sodium dodecyl sulfonate (SDS) treatment approach. The SDS treatment resulted in increased functionalities, and ion exchangeable sites of macadamia nutshells leading to enhanced the removal of methylene blue (MB) dye from water. Factors such as pH (2-11), contact time (1-360 min), initial MB dye concentration (30-385 mg/L), and adsorbent mass (0.02 – 0.18 g/L), were tested in this study. The enhanced removal of MB removal (≥ 90%) was synergistically influenced by pH, with optimum adsorption removal around pH 7 to 11 for the SMS adsorbent. The results showed that MB removal was fast with SMS, and that the equilibrium was reached in 80 min. The batch adsorption results showed a good fit with pseudo-first-order kinetics, and the Langmuir isotherm model, in agreement with the experimental values, with a maximum adsorption capacity of 195.97 mg/g for MB. Surfactant modified macadamia nutshells (SMS) composed of surface functional groups: –OH, –C = O, -C-O, and multiple carbon-carbon bond, all contributed to synergistic mechanism interaction between the adsorbent and MB dye in this study. This study thus suggested that the SMS could be highly beneficial for eliminating anionic dye from polluted water-based solutions, thus highlighting its potential for practical usage in large pollutants removal