Exploring the Potential of Locally Sourced Fungal Chitosan for Paper Mechanical Property Enhancement

Abstract

This study investigated the potential of locally sourced mushrooms as a sustainable alternative to marine-derived chitosan in papermaking. Chitosan was extracted from four local (Boletus edulis, Suillus luteus, Leccinum aurantiacum, Suillus variegatus), one commercially available (Agaricus bisporus) and one laboratory-grown (Phanero-chaete chrysosporium) fungal species. Paper handsheets were prepared using either 100% regenerated paper or a 50/50 blend of regenerated paper and hemp fibres. 2.5% chitosan (based on dry mass) was incorporated into the paper mass, using chitosan sourced from B. edulis, A. bisporus, P. chrysosporium, and crustacean chitosan. Fungal chitosan sources were selected based on multiple factors. B. edulis exhibited the highest chitosan yield (5.03%), the highest degree of deacetylation (77.0%) and the highest molecular weight (59.18 kDa). It is also a widely prevalent species in the Baltic region. A. bisporus demonstrated the highest degree of crystallinity (62.7%). Additionally, it has readily available waste material due to its popularity in the food industry. P. chysosporium, with its low degree of crystallinity (33.9%) and small molecular weight (9.06 kDa), is easily cultivable in laboratory conditions. Mechanical testing of papers showed that fungal chitosan significantly improved tensile index and elongation at break (in wet and dry states) and burst strength while reducing air permeability. Notably, fungal chitosan con-sistently outperformed crustacean chitosan. Commercially available A. bisporus and locally sourced B. edulis emerged as promising alternatives to crustacean chitosan in papermaking. Further research is needed to explore other applications for fungal chitosan.