[Development of a new composite biomaterial based on filamentous fungal mycelium for 3D printing]

[The construction industry is one of the main contributors to environmental pollution due to its significant carbon footprint. Consequently, there is a need to find ways to mitigate the negative impact associated with this economic activity. One solution is the use of materials derived from natural sources, presenting themselves as an alternative to conventional materials, given their high energy consumption and use of increasingly scarce natural resources. Mycelium composites (MCCs) are an example of these new options; however, their applications are limited by the common molding manufacturing method. The overall objective of this research is the development of a mycelium-composite biomaterial that allows for the fabrication of structures using 3D printing. Simultaneously, the project seeks to repurpose lignocellulose-rich organic waste as a carbon source to support the solid-state cultivation of the Ganoderma lucidum fungus. The ink formulation is optimized by studying its rheology and adjusting its viscosity. To this end, the behavior of the ink was evaluated after the addition of chitosan or alginate as binders. Chitosan concentrations of 2% w/w and 3% w/w were tested, along with four different alginate concentrations: 4% w/w, 10% w/w, 12% w/w, and 14% w/w. Extrusion tests were also performed on oak sawdust and corn cob substrates. Finally, a prototype was chosen for printing with a bio-ink composed of 14% w/w alginate and inoculated corn cob. The structure was incubated for three weeks at a temperature range of 25°C-30°C, resulting in surface colonization of the substrate by the mycelium. Test specimens were then constructed from the printed material for tensile-deformation and compression testing. The mechanical properties of the biomaterial increased significantly compared to the hydrogel with the pure substrate, improving its elastic modulus by over 100% and its compressive strength by approximately 45%. Therefore, it can be concluded that progress has been made in the fabrication of mycelium biocomposites using 3D printing.]