Kinetics of antibacterial activities of cellulose nanocrystals and their silver-zinc oxide nanocomposites: Application as potential disinfectants

Cellulose nanocrystals (CNCs) were produced from corncob and used as reducing agent in the formation of ZnO/CNCs, Ag/CNCs, and  ZnO-Ag/CNCs composites and applied as antibacterial agents for both grampositive and gram-negative bacteria and the kinetics of  microbial growth inhibition studied. The CNCs and composites were characterized by UV-visible and Fourier transform-infrared (FTIR)  spectroscopy. The characterization results revealed that the functional groups of CNCs were affected by their interactions with Ag+  and Zn2+ ions. The composites at 100 mg/mL displayed activities against Gram-positive bacteria - Bacillus subtilis, Staphylococcus aureus,  Staphylococcus epidermis, Bacillus coagulans and Enterococcus faecalis and Gram-negative bacteria - Escherichia coli, Klebsiella pneumonia,  Salmonella typhimurium, Pseudomonas aeruginosa, Enterococcus faecium and Acinetobacter baumanii) bacteria with inhibitory zones ranged  between 9-46 mm. The kinetics of inhibition showed that the composites treated water had 4 to 28 times lower rate constants compared  to the untreated water. This implied that the composites inhibit growth rates and have the potential of disinfecting for between 4 to 28 h  depending on the bacteria. The materials showed better growth inhibition rate on gram-positive bacteria than on gram-negative. These  composites may have potential applications as disinfectants in personal care products and serve as more eco-friendly alternative  disinfectants to chlorophenols.