Antibacterial and antioxidative activity of chitosan and chitosan hydrochloride isolated from mushrooms

Abstract

Chitosan is a linear polysaccharide formed from β-D-glucosamine randomly distributed chains and N-acetyl-D-glucosamine, which is obtained in the process of deacetylation of chitin. Only a small number of mushrooms have chitosan as one of the components in their cell wall. It is assumed to exhibit antimicrobial, antifungal and antiviral activity. The task of this research was to test the antioxidant and antibacterial activity of commercial products chitosan (Aldrich, Germany) and chitosan hydrochloride (Glentham Life Sciences, UK). The degree of deacetylation of both products was about 85%. Commercially, Agaricus bisporus is mostly used for chitosan production. The antibacterial potential was tested by the microdilution method (2.5-0.019 mg/mL) using one Gram-positive bacteria Enterococcus faecalis ATCC 29219 and one Gram-negative Escherichia coli ATCC 25922 and the reduction of the number of microorganisms was monitored using the highest tested concentrations of 2.5 mg/mL samples. Chitosan and chitosan hydrochloride showed a significant effect on the tested microorganisms. The minimal inhibitory (MIC) concentration of chitosan hydrochloride against E. coli was 1.25 mg/mL, while a concentration of 2.5 mg/mL was the minimal bactericidal concentration (MBC) for the same bacteria, while the MIC against E. faecalis was a concentration of 2.5 mg/mL. There was also a complete reduction in the number of E. coli. Commercial chitosan had a stronger effect on E. faecalis (MIC 1.25 and MBC 2.5 mg/mL), than on E. coli where a significant growth inhibition was also observed (MIC 2.5 mg/mL, MBC was not detected for the tested concentrations). The function of antioxidants is to remove reactive oxygen species and to prevent the occurrence and spread of oxidative stress. By examining the antioxidant activity, the absence of DPPH radical scavenging ability was determined for the tested samples with a concentration of 5mg/ml, while the ability to chelate Fe2+ was low and amounted to 27.22 % for chitosan and 41.56 % for chitosan hydrochloride. In further research, it is necessary to find the best way to extract chitosan from mushrooms in order to obtain samples with pronounced biological activity.