EUROPEAN CONGRESS AND EXHIBITION ON ADVANCED MATERIALS AND PROCESSES - EUROMAT 2021

Networks formed of natural nano-fibrils are an appealing approach to integrate the advantages of nano-scale fibers with sustainable raw materials. Whereas cellulose nanofibrils are already widely applied, nanofibrillated chitin is lagging behind this development. Chitin is commonly derived from crustaceans, necessitating harsh and prolonged chemical and mechanical processes for the isolation of nanofibrils. Opposed to that, fungal chitin, coming in a natural complex with glucan, is easily accessible by mild extraction methods. The structural component of fungal cell walls comprises of chitin nanofibrils covalently bond to glucan thus constituting a native nano-fibrous composite material (chitin-glucan, CG) combining the strength of chitin and the toughness of glucan. Isolation of such fungal chitin nanofibrils (FChNF) does not require energy-intensive extraction methods as necessary for the extraction of cellulose nanofibrils or chitin nanofibrils of crustacean origin. FChNF can also be derived from mycelium, the vegetative part of fungi. Thus, fungal growth can be utilized as low-cost source for on-demand generation of natural nanofibrils that are subsequently utilized in the formation of nanostructured networks.

Here, we extracted natural polymers from white button mushrooms (Agaricus bisporus), tree-bracket fungi (Daedaleopsis confragosa) and mycelium grown on sugarcane by-product molasses. A mild alkaline extraction process was applied and isolated polymer fibrils processed into nanopaper networks. Extracted polymers and nanopapers were characterized regarding their surface characteristics and mechanical properties.

Fungal extracts were readily disintegrated into nanofiber dimensions by low-energy mechanical blending, preserving the native quality of the CG complex. Mechanical properties of CG nanopapers were determined by the nanostructure of the network with glucan playing a crucial role. Furthermore, hydrophobic surface properties originated from the composition of the nanopapers. Biopolymers prepared from these resources are applicable in a wide range of applications from packaging over filtration membranes to composites.