The antibacterial activity of ceramsite coated by silver nanoparticles in micropore

Effective removal of methylene blue dye from water with nanocomposite ceramsites in a fixed-bed column

The study aims to remove methylene blue dye from water with a fixed-bed column packed with Cu₂O nanocomposite ceramsites. The column showed the advantages of fixed-bed column adsorption and photocatalytic oxidation. The Cu₂O nanocomposite ceramsites with strong photocatalytic oxidation activity and well-developed porous structure were successfully prepared with the chemical vapour deposition process, which also met with the China's industrial standard of CJ/T 299-2008 and China's national standard of GB 5085.3-2007. In the column experiments under the experimental conditions (initial pH was 3, reaction temperature was 25°C and flow rate was 33 mL/min), the breakthrough curve was much more smooth. The breakthrough time and saturation time under ultraviolet radiation were 36.0% and 26.83% longer than those under the conditions without ultraviolet radiation, because the micro-pore structure of ceramsite was closely related to optical excitation properties of nano-Cu₂O. The Yoon-Nelson and Adams-Bohart models were applied to describe the obtained breakthrough curves using non-linear regression, in which the Yoon-Nelson model gave the better prediction results for breakthrough curves, with R²>0.98. Besides, amines were the dominant intermediates at saturation point and final products were inorganic anions. This study confirmed that the fixed-bed column packed with Cu₂O nanocomposite ceramsites could efficiently treat methylene blue dye wastewater, due to the structure-function relationship between ceramsite and nano-Cu₂O.

Antibacterial Activity of Shikimic Acid from Pine Needles of Cedrus deodara against Staphylococcus aureus through Damage to Cell Membrane

Shikimic acid (SA) has been reported to possess antibacterial activity against Staphylococcus aureus, whereas the mode of action of SA is still elusive. In this study, the antibacterial activity and mechanism of SA toward S. aureus by cell membrane damage was investigated. After SA treatment, massive K⁺ and nucleotide leakage from S. aureus, and a significant change in the membrane potential was observed, suggesting SA may act on the membrane by destroying the cell membrane permeability. Through transmission electron microscopic observations we further confirmed that SA can disrupt the cell membrane and membrane integrity. Meanwhile, SA was found to be capable of reducing the membrane fluidity of the S. aureus cell. Moreover, the fluorescence experiments indicated that SA could quench fluorescence of Phe residues of the membrane proteins, thus demonstrating that SA can bind to S. aureus membrane proteins. Therefore, these results showed the antibacterial activity of SA against S. aureus could be caused by the interactions of SA with S. aureus membrane proteins and lipids, resulting in causing cell membrane dysfunction and bacterial damage or even death. This study reveals the potential use of SA as an antibacterial agent.