Filamentous fungi can be used for the valorization of food waste as a value-added product. The goal of this study was the valorization of bread waste through fungal cultivation and the production of value-added products. The fungal cultivation was verified for upscaling from shake flasks to a bench-scale bioreactor (4.5 L) and a pilot-scale bioreactor (26 L). The fungus showed the ability to grow without any additional enzymes or nutrients, and it was able to consume a bread concentration of 4.5% (w/v) over 48 h. The biomass concentration in the shake flasks was 4.1 g/L at a 2.5% bread concentration, which increased to 22.5 g/L at a 15% bread concentration. The biomass concentrations obtained after 48 h of cultivation using a 4.5% bread concentration were 7.2–8.3 and 8.0 g/L in 4.5 and 26 L bioreactors, respectively. Increasing the aeration rate in the 4.5 L bioreactor decreased the amount of ethanol produced and slightly reduced the protein content of the fungal biomass. The initial protein value in the bread was around 13%, while the protein content in the harvested fungal biomass ranged from 27% to 36%. The nutritional value of the biomass produced was evaluated by analyzing the amino acids and fatty acids. This study presents the valorization of bread waste through the production of a protein- and fatty-acid-rich fungal biomass that is simultaneously a source of microfibers.

Here, cell wall of a zygomycete fungus, Rhizopus delemar, grown on bread waste was wet spun into monofilaments. Using the whole cell wall material omits the common chitosan isolation and purification steps and leads to higher material utilization. The fungal cell wall contained 36.9% and 19.7% chitosan and chitin, respectively. Solid state NMR of the fungal cell wall material confirmed the presence of chitosan, chitin, and other carbohydrates. Hydrogels were prepared by ultrafine grinding of the cell wall, followed by addition of lactic acid to protonate the amino groups of chitosan, and subsequently wet spun into monofilaments. The monofilament inhibited the growth of Bacillus megaterium (Gram+ bacterium) and Escherichia coli (Gram- bacterium) significantly (92.2% and 99.7% respectively). Cytotoxicity was evaluated using an in vitro assay with human dermal fibroblasts, indicating no toxic inducement from exposure of the monofilaments. The antimicrobial and biocompatible fungal monofilaments, open new avenues for sustainable biomedical textiles from abundant food waste.