Food systems have the potential to improve human health while contributing to environmental sustainability; however, they are currently endangering both. The current food system, which is often based on animal farming, is responsible for global greenhouse gas emissions, and increases the incidence of, and mortality from, non-communicable diseases. Providing the growing global population with healthy food from sustainable systems is an urgent requirement. Microbial fermentation is expected to play a significant role in the transition to sustainable and healthy food systems. Microorganisms, such as edible filamentous fungi, can be a part of the solution. The versatility of filamentous fungi enables them to grow on a variety of substrates in submerged or solid-state fermentation, which minimizes substrate limitations, as well as exhaustive land and water requirements in the cultivation process. In this thesis, the potential of filamentous fungi in the production of sustainable and healthy food, and optimization of fungal biomass production through submerged fermentation on synthetic glucose- and oat-based media, were studied. Additionally, scale-up, sensory characteristics, and nutritional profiles were assessed.

In order to evaluate the production of sustainable and healthy food from filamentous fungi, Aspergillus oryzae, a fungus that is commonly used in food production, was cultivated on oat flour in a pilot-scale airlift bioreactor. The nutrient-rich fungal biomass obtained by increasing the protein content was characterized by an improved ratio of essential amino and fatty acids, and an increase in dietary fiber, minerals, and vitamins. Fungal biomass was converted to Burger patties with minimal downstream processing, which were then subjected to sensory evaluation using an untrained panel. Inspired by the ability of filamentous fungi to produce different bioactive compounds, four strains of edible filamentous fungi commercially used in food production, namely, Aspergillus oryzae, Rhizopus oryzae, Neurospora intermedia, and Rhizopus oligosporus, were cultivated in a semi-synthetic medium using submerged fermentation to screen for the synthesis of the bioactive compound L-carnitine. The formation of L-carnitine can be enhanced by modulating various factors, such as the fungal strain, cultivation time, and the presence of yeast extract. Aspergillus oryzae was found to have a much greater potential for L-carnitine production than Rhizopus sp and Neurospora intermedia.

In terms of moving towards a sustainable and healthy food supply system, this thesis might contribute not only industrially but also in terms of policy development.