From purposeless residues to biocomposites: A hyphae made connection

Abstract

Biocomposites create attractive alternatives to match packing needs with available agricultural residues. Growing native fungal strains developed a mycelium biocomposite over a mixture of Peach Palm Fruit Peel Flour and Sugar Cane Bagasse Wet Dust. A methodology was proposed to analyze their main characteristics: 1) morphological, 2) chemical, and 3) biodegradability. 1) SEM analysis evidenced the structural change of the dried vs pressed material and mycelium morphology for both species. 2) The ratio lignin:carbohydrate showed that P. ostreatus degrades the cellulose-hemicellulose fraction of the substrate at a higher rate than T. elegans, and 3) the curve BMP indicated that these materials are readily biodegradable with a maximum yield of 362,50 mL biogas/g VS. An innovative tangible valorization strategy based on mass balances is also presented: from just 50 kg of peel flour, up to 1840 units can be manufactured, which could pave the way for a more sustainable future.

Keywords: Agroindustrial waste; Biocomposites; Fungal mycelium; Pleurotus ostreatus; Trametes elegans.

Graphical abstract

Fig. 1

Obtained biocomposites corresponded to Dry Pleurotus ostreatus (DPO), Pressed Pleurotus ostreatus (PPO), Dry Trametes elegans (DTE) and Pressed Trametes elegans (PTE). * Pleurotus ostreatus (PO); ** Trametes Elegans (TE); Images colored to highlight Mycelium, SCB Wet Dust.

Fig. 2

SEM images of biocomposites (a) P. ostreatus (scale bar is 20 µm). (b) P. ostreatus (scale bar is 10 µm). (c) P. ostreatus hyphae diameter distribution with mean 2,5 ± 0,36 µm. (d) T. elegans (scale bar is 20 µm). (e) T. elegans (scale bar is 10 µm). (f) T. elegans hyphae filament diameter distribution with mean 3,10 ± 0,09 µm.

Fig. 3

FTIR-ATR spectra of biocomposites obtained. a) Substrates before being inoculated: Main assignations of PPF Peel Flour (green), SCB Wet Dust (red), Mix of PPF Peel Flour and SCB Wet Dust (black). b) Mycelium samples after growth: Main assignations of P. ostreatus (yellow) and T. elegans (blue) are included.

Fig. 4

Ratio of relatives intensities $I_{1510}/I_{895}$ Lignin:cellulose $I_{1510}/I_{1158}$ Lignin:hemicellulose $I_{1510}/I_{1375}$ Lignin:chitin Standard deviation is performed with duplicate samples (mean ± one standard deviation). Mix P. ostreatusT. elegans.

Fig. 5

Anaerobic biodegradability of P. ostreatus samples. (a) BMP, (b)% DEG. Standard deviation is performed with duplicate samples (mean ± one standard deviation). Equal letters indicate no significant difference according to Tukey's test at p ≤ 0.05. Pleurotus ostreatus drying Pleurotus ostreatus pressed.

Fig. 6

Schematic diagram of the process from substrates to biocomposites detailing the dry mass balance.