Contribution of chitosan–caffeic acid graft against Staphylococcus aureus on oxidative stress and cell membrane

This study aimed to explore the antibacterial activity and mechanism of chitosan-caffeic acid graft (CS-g-CA) against Staphylococcus aureus (S. aureus). The minimum inhibitory concentration of CS-g-CA against S. aureus was assessed. The results of scanning electron microscope and confocal laser scanning microscope showed that CS-g-CA treatment could destroy the cell morphology and cause the leakage of intracellular contents, leading to bacteria death. The changes of superoxide dismutase, catalase, reactive oxygen species (ROS), and lipid peroxidation indicated that CS-g-CA stimulated the oxidative stress system of the cell, which further induced the generation of ROS, aggravated the accumulation of lipid peroxide, and destroyed the structure of the inner membrane. The electrophoresis results showed that the DNA of bacteria treated with CS-g-CA was broken led to the death of microorganisms. Overall, CS-g-CA has the potential to be a substitute for new bio-preservative with bacteriostatic effects in food industry.