Bioconversion of food waste to biocompatible wet-laid fungal films

The fungus Rhizopus delemar grown on bread waste, in a submerged cultivation process, was wet-laid into films. The fungal cell wall was isolated by alkali or enzymatic treatments. The biomass was also subjected to a heat treatment to deactivate biological activity. Treated biomass was homogenized by an iterative ultrafine grinding process and finally cast into films by a wet-laid process. Ultrafine grinding improved the densification of films and they showed tensile strengths of up to 18.1 MPa, a Young’s modulus of 2.3 GPa and a strain at break of 1.4%. Alkali treatment resulted highest tensile strength, with SEM images showing a dense and highly organized structure. In contrast, enzymatic or heat treatments resulted in films with less organized structures. Biocompatibility of fungal films was confirmed by a cell viability assay and fluorescent staining.