Filamentous fungi are an amazing group of microorganisms able to both degrade and produce a plethora of different compounds. Many fungi have rather modest nutritional requirements, making them very interesting for biotechnological applications, with applications in both submerged and solid-state fermentation. Applications include agriculture, food, and feed, pharmaceutical, pulp and paper, textile industries, as well as a potential for waste valorization. Some of the current and potential products include: ethanol, citric acid, gluconic acid, itaconic acid, lactic acid, fumaric acid, and the fungal biomass as a food or feed, as well as more specific compounds such as enzymes.

Fungal biomass (FB), a by-product of the fermentation processes produced in large volumes, is a promising biomaterial that can be incorporated into poly(lactic acid) (PLA) to develop enhanced biocomposites that fully comply with the biobased circular economy concept. The PLA/FB composites, with the addition of triethyl citrate (TEC) as a biobased plasticizer, were fabricated by a microcompounder at 150 °C followed by injection molding. The effects of FB (10 and 20 wt %) and TEC (5, 10, and 15 wt %) contents on the mechanical, thermal and surface properties of the biocomposites were analyzed by several techniques. The PLA/FB/TEC composites showed a rough surface in their fracture section. A progressive decrease in tensile strength and Young’s modulus was observed with increasing FB and TEC, while elongation at break and impact strength started to increase. The neat PLA and biocomposite containing 10% FB and 15% TEC exhibited the lowest (3.84%) and highest (224%) elongation at break, respectively. For all blends containing FB, the glass transition, crystallization and melting temperatures were shifted toward lower values compared to the neat PLA. The incorporation of FB to PLA thus offers the possibility to overcome one of the main drawbacks of PLA, which is brittleness.