Naturally Multicomponent Materials Obtained from Filamentous Fungi: Impact of Different Cell Rupture Treatment on Film Properties

Abstract

This study aimed to obtain films using the entire mycelium of Aspergillus niger, Mucor hiemalis, and Penicillium nalgiovense by casting method and to evaluate the effect of different cell rupture treatments. Mycelia crude protein and total glucans content were determined. Dispersions at 3% wt (on a dry basis) of sterilized mycelium were treated with ultrasound and/or high-speed homogenisation and characterized by particle size distribution and optical microscopy. Films were prepared by casting, adding glycerol, and characterized by mechanical properties, thermogravimetric profiles, Fourier-transform infrared spectra, colour, and opacity. The micrographs of Penicillium nalgiovense and Aspergillus niger showed a greater hyphae fragmentation when ultrasound time increased, achieving a monomodal population (% volume) by 30-min ultrasound. It was feasible to obtain homogeneous films with good handleability from all treated dispersions regardless of the rupture condition, except for those of Penicillium nalgiovense obtained by 15-min ultrasound. Different cell disruption treatments did not impact the colour or opacity of films. Spectra showed greater similarity between Penicillium nalgiovense and Aspergillus niger than with Mucor hiemalis, which was consistent with the composition obtained. The mechanical properties did not differ according to the rupture treatments. Mucor hiemalis films showed the lowest tensile strength and elongation at break, while Aspergillus niger films showed the highest Young’s modulus. Thermogravimetric analyses showed a multiple degradation profile depending on the fungal strain and the rupture cell treatments applied. The results obtained show the potential use of entire mycelium for the development of new bio-based materials and encourage further studies on this research line.