MYCELIUM COMPOSITES WITH AGRO-INDUSTRIAL BY-PRODUCTS AS A SUSTAINABLE ALTERNATIVE TO EXPANDED POLYSTYRENE (EPS) FOR FOOD PACKAGING

The development of sustainable alternatives to expanded polystyrene (EPS) is a growing demand in the food packaging sector. In this context, mycelium-based composite materials have been developed as alternatives to EPS. Agro-industrial byproducts such as sugarcane bagasse (SCB) and wheat bran (WB) show potential for generating semi-rigid composite materials based on fungal mycelium. This work aimed to develop semi-rigid composites produced by cultivating Trametes versicolor mycelium in mixtures of SCB and WB, aiming at applications as sustainable analogs to EPS for food packaging. Three substrate formulations were prepared: 50% SCB and 50% WB (S50W50), 75% SCB and 25% WB (S75W25), and 100% SCB (S100W0). The mycelium was inoculated into these mixtures and transferred to square molds, where it was allowed to grow for 11 days. After the growth period, the samples were dried at 90 °C for 24 h. Specimens were then obtained and characterized in terms of moisture exposure, apparent density, porosity, compressive strength, contact angle, X-ray computed tomography (CT), and optical and scanning electron microscopy (SEM). When exposed to moisture, water absorption increased with higher WB content, indicating its greater moisture retention capacity. Apparent density decreased as the SCB fraction increased. Although densities were higher than that of EPS, they were lower than those reported for other mycelium composites, suggesting higher porosity. In addition, all composites presented high porosity (84%–93%), which may indicate good thermal insulation, an important characteristic of EPS. In compression tests, the composite containing 50% SCB and 50% WB showed the best mechanical performance. Anyway, all formulations outperformed EPS, highlighting their potential for applications such as trays, where compressive strength is essential. The composites exhibited higher contact angles than EPS, possibly due to the presence of a hydrophobic mycelial surface layer. Microscopy and X-ray tomography confirmed the formation of a mycelial surface layer and the presence of internal porosity. These results demonstrate that it was possible to produce mycelium composites with low apparent density, high porosity, compressive strength higher than that of EPS, and potential biodegradability, characteristics that reinforce their potential as substitutes for EPS, particularly in formulations with higher sugarcane bagasse content.