Characterization of chitosan and chitosan–glucan complex extracted from the cell wall of fungus Gongronella butleri USDB 0201 by enzymatic method

The fungus Gongronella butleri USDB 0201 was grown on sweet potato pieces supplemented with mineral and urea solution. Mycelia were harvested after 7 days of cultivation. Chitosan in the fungal cell wall exists in two forms, free chitosan and chitosan bounded to β-glucan. The linkage between chitosan and β-glucan in the chitosan–glucan complex (CGC) was successfully cleaved using a heat stable α-amylase. The resultant chitosan and β-glucan polymeric moieties were characterized. Data from elementary analysis, IR and 13C NMR spectroscopy confirmed that all intramolecular glycosidic linkages in either chitosan or glucan polymeric moieties are in the β-configuration. Data from specific enzymatic degradation of the CGC obtained from different treatments and reducing sugar analysis indicate that chitosan and glucan are linked by an intermolecular α-1,4 glycosidic bond. These evidences supported to prove the β-linked chitosan and β-linked glucan are linked with α-1,4 glycosidic bond. However heat stable α-amylase enzyme could not cleave the CGC completely. Therefore high yield with pure chitosan could be obtained from the cell wall of fungus G. butleri USDB 0201 by Termamyl enzyme treatment.