ABSTRACT
To assess the adaptability of chitosan (from agricultural waste) as a natural disinfectant, its antibacterial activity against bacteria associated with waterborne diseases was investigated by varying such abiotic conditions, as pH and ionic strength and by adding different amounts of acid solvent, metal ions, and EDTA. Two major waterborne pathogens, Escherichia coli and Staphylococcus aureus, were examined. Results showed that organic acids with low carbon number were better solvents for chitosan than were inorganic acids. The effect of pH below 6 on the antibacterial activity of chitosan was significant. The antibacterial activity of chitosan increased with ionic strength but decreased with the addition of metal ions. The addition of Zn(2+) ions inhibited the antibacterial activity of chitosan the most, while the addition of Mg(2+) ions inhibited the antibacterial activity of chitosan the least. This was due to the chelating capacity of chitosan toward metal ions. The antibacterial activity of chitosan against E. coli was enhanced by EDTA. However, the antibacterial activity of chitosan against S. aureus was partially suppressed by EDTA. The antibacterial activity of chitosan was also dependent on its charges and solubility. The antibacterial mechanism of chitosan has currently been hypothesized as being related to surface interference. The results show that the chitosan is a potential bactericide under various environmental conditions.
Subject(s)
Anti-Bacterial Agents/pharmacology , Chitin/analogs & derivatives , Chitin/pharmacology , Escherichia coli/drug effects , Staphylococcus aureus/drug effects , Water Microbiology , Acids/pharmacology , Chitosan , Culture Media , Edetic Acid/pharmacology , Hydrogen-Ion Concentration , Ions/pharmacology , Metals/pharmacology , Osmolar Concentration , Solvents/pharmacologyABSTRACT
The antimicrobial properties of chitosan, a derivative of chitin, were investigated in the solid and liquid culture against bacteria associated with waterborne disease in order to assess the potential for using chitosan as a natural disinfectant. Six strains which included three gram-negative and three gram-positive bacteria were studied. The effects of the deacetylation degree, concentration, and molecular weight of chitosan on antibacterial activities were assessed. Chitosan exhibited the highest antibacterial activity against the Pseudomonas aeruginosa on the solid agar. Similar tendency was found when the bacteria were cultivated in liquid broth. The higher deacetylation degree and higher concentration of chitosan cause the higher antibacterial activities. The effect of molecular weight of chitosan on the inhibition efficacy of bacteria is dependent on the species of bacteria. Escherichia coli is sensitive to chitosan during its death phase and logarithmic phase. The antibacterial mechanism of chitosan was illustrated by the surface charge and persistence length. Results indicated that chitosan is potential as a natural disinfectant.
