Antibacterial action of chitosan

TLDR

The study examined the antibacterial action of chitosan hydroglutamate, chitosan lactate, and fungal‑derived chitosan against gram‑negative and gram‑positive bacteria. Chitosan permeabilizes bacterial membranes, causing cell agglutination and intracellular leakage, while complexation with polygalacturonate blocks its penetration and activity. Within one hour, CH and CL inactivated bacteria by one to five log cycles, with 0.1 mg/mL being most effective, whereas fungal chitosan was less potent, and microscopy revealed cell agglutination at pH 5.8.

Abstract

Abstract The antibacterial action of chitosan hydroglutamate (CH), chitosan lactate (CL) and chitosan derived from fungal mycelia was examined against both gram‐negative and gram‐positive bacteria. Plate counts indicated inactivation rates of one‐ to five‐log‐cycles within one hour. Fungal chitosan had significantly less antibiotic effect than CH and CL. The antibacterial action of CH and CL was very similar and shown to be concentration dependent with 0.1 mg/mL more effective than 2.0 and 5.0 mg/mL. When CH (or CL) and polygalacturonate were added to cell suspensions, death was prevented, possibly indicating that chitosan complexed with polygalacturonate could not penetrate the cell or disrupt the membrane. Leakage of intracellular components caused by chitosan was determined by exposing lactose‐induced Escherichia coli to chitosan with assay for ß‐galactosidase activity indicating that cell permeabilization occurred more extensively at the low chitosan concentrations. Microscopic examination showed that chitosan caused cell agglutination at pH 5.8. Injury to chitosan‐exposed Staphylococcus aureus MF‐31 could not be demonstrated using the criterion that sublethally stressed cells have increased sensitivity to high levels of sodium chloride.