Characterization of Novel Biopolymer Blend Mycocel from Plant Cellulose and Fungal Fibers

Abstract

In this study unique blended biopolymer mycocel from naturally derived biomass was developed. Softwood Kraft (KF) or hemp (HF) cellulose fibers were mixed with fungal fibers (FF) in different ratios and the obtained materials were characterized regarding microstructure, air permeability, mechanical properties, and virus filtration efficiency. The fibers from screened Basidiomycota fungi Ganoderma applanatum (Ga), Fomes fomentarius (Ff), Agaricus bisporus (Ab), and Trametes versicolor (Tv) were applicable for blending with cellulose fibers. Fungi with trimitic hyphal system (Ga, Ff) in combinations with KF formed a microporous membrane with increased air permeability (>8820 mL/min) and limited mechanical strength (tensile index 9-14 Nm/g). HF combination with trimitic fungal hyphae formed a dense fibrillary net with low air permeability (77-115 mL/min) and higher strength 31-36 Nm/g. The hyphal bundles of monomitic fibers of Tv mycelium and Ab stipes made a tight structure with KF with increased strength (26-43 Nm/g) and limited air permeability (14-1630 mL/min). The blends KF FF (Ga) and KF FF (Tv) revealed relatively high virus filtration capacity: the log₁₀ virus titer reduction values (LRV) corresponded to 4.54 LRV and 2.12 LRV, respectively. Mycocel biopolymers are biodegradable and have potential to be used in water microfiltration, food packaging, and virus filtration membranes.

Keywords: air permeability; fungal fibers; hemp fibers; mechanical properties; microstructure; mycocel; softwood fibers; virus membrane filtration.

Figure 1

Schematic representation of the virus filtration test (technical details are provided in text). (1) 1.5 cm × 1.5 cm filter sample is cut out from each material, folded into the form of a conical funnel, and placed into a 1.5 mL tube; (2) 50 µL of recombinant Semliki forest virus (SFV)-enh/Luc virus solution (107 i.u./mL) is added into the cone; (3) the tube is centrifuged to allow the virus to pass through the material; (4) the filtrate (indicated by arrow) is collected; (5) the filtrated is diluted and used for cell infection in a 24-well cell culture plate; (6) after overnight incubation of the plate the cell lysates are prepared and the virus infection is measured by detection of the luciferase activity in infected cells (luminometry). The cell infection with the standard dilutions of the virus is used to generate a standard curve and to calculate the amount of virus in the filtrate.

Figure 2

Microstructure (left column) and macrostructure (right column) of mycocel biopolymer compositions made of Kraft fibers (KF), hemp fibers (HF), and fungal fibers (FF): (a) KF FF (Ff); (b) KF FF (Ga); (c) KF FF (Tv); (d) KF FF (Ab); (e) KF HF FF (Ga). Microimages show flat hemp and softwood fibers (10–30 μm) (a–e) and narrow fungal fibers (2–7 μm) of polypores (a–c,e) and swollen hyphae (7–20 μm) of agaric (d). LM, 200×. Bar = 100 μm.

Figure 2

Microstructure (left column) and macrostructure (right column) of mycocel biopolymer compositions made of Kraft fibers (KF), hemp fibers (HF), and fungal fibers (FF): (a) KF FF (Ff); (b) KF FF (Ga); (c) KF FF (Tv); (d) KF FF (Ab); (e) KF HF FF (Ga). Microimages show flat hemp and softwood fibers (10–30 μm) (a–e) and narrow fungal fibers (2–7 μm) of polypores (a–c,e) and swollen hyphae (7–20 μm) of agaric (d). LM, 200×. Bar = 100 μm.

Figure 3

Ultrastructure of raw materials (left column) from (a) Kraft fibers (KF), (b) hemp fibers (HF), and (c) fungal fibers (FF Ga), and mycocel biopolymer compositions (right column): (d) KF FF (Ga); (e) HF FF (Ga); (f) KF HF FF (Ga). SEM, 1000×. Bar = 100 μm.