Chitosan–Glucan Complex from Fruiting Bodies of Higher Fungi as a Base for Functional Film Hybrid Biocomposites

Abstract

The use of fungal raw materials for preparing various biocomposites is a promising research direction. Data on using fungal raw materials for preparing chitosan, in particular, films based on the chitosan–glucan complex, are insufficient, which determined the goal of this study. Chitin from fungal biomass, converted to chitosan by deacetylation, shows promise for preparing functional film hybrid polymer biocomposite materials. This study deals with film samples based on the chitosan–glucan complex obtained from the biomass of fruiting bodies of higher fungi. The study was aimed at preparing film materials based on the chitosan–glucan complex and at determining their structure and mechanical and physicochemical properties. The chitosan–glucan complex (CtsGC) was prepared by base hydrolysis of the chitin–glucan complex, and film materials, by wet forming onto a support. The mechanical and physicochemical properties were studied using thermogravimetric analysis, differential scanning calorimetry, and thermomechanical analysis. The film microstructure was examined using scanning electron microscopy. The forming resulted in significant texturing of the external surface relief: (1) interwoven fibrous thickenings consisting of residues of incompletely dissolved CtsGC particles are clearly seen; (2) there are closed micropores with the transverse size from 100 to 1000 nm; (3) there are local flat druses of lamellar crystals. The tensile strength of the film is up to 2.9 MPa, the elastic modulus is up 70 MPa, and the relative elongation at break is up to 14%. The water content of the film reaches 15 wt %. The product is thermally stable up to 200℃ and then gradually degrades in several steps. The results can be used for (1) preparing experimental samples of hybrid biocomposite films with various fillers, (2) assessing the possibilities of using biocomposite films, and (3) developing a future integrated technology for processing the readily renewable non-food vegetable resources into products demanded by the Russian economy.