LAUSR

In the present research, an optimized liquid medium which had no neutralizing effect to chitosan was developed. Moreover, magnesium chloride (MgCl2) was identified to be able to absolutely neutralize the antibacterial activity of chitosan and its derivatives. Took the two results together, the minimum bactericidal concentration (MBC) and minimum inhibitory concentration (MIC) of chitosan were precisely quantified through a further improved method based on the optimized medium and the relation curve between antibacterial rate and reaction time was obtained with the help of MgCl2 neutralizer. The MBC and MIC of chitosan were all 30 μg/mL against Staphylococcus aureus and Escherichia coli, and 100 μg/mL of chitosan acetate could reach 100 % of antibacterial rate within 3 min. Furthermore, coordination between magnesium ions and chitosan as well as reduced zeta potential of chitosan caused by coordination were inferred to be the neutralizing mechanism of MgCl2 neutralizer.