Filamentous Fungi for Polyunsaturated Fatty Acid Production: From Strain Resources to Metabolic Engineering

Polyunsaturated fatty acids (PUFAs) play critical physiological roles in maintaining cardiovascular health, neurodevelopment, and immune regulation, with continuously growing market demand. Traditional supply chains based on fish oil and plant oils face severe challenges including resource depletion, environmental pollution, and sustainability concerns. Single cell oil production via fermentation using filamentous fungi has emerged as a sustainable and economically viable alternative. This review provides a comprehensive overview of research progress on PUFA synthesis by filamentous fungi, covering strain resources, biosynthetic pathways, regulatory mechanisms, major product development, and industrialization prospects. Filamentous fungi have formed a complete spectrum from native high-yielding strains (e.g., Mortierella alpina, Mucor circinelloides, Umbelopsis isabelline, Thamnidium elegans, Cunninghamella echinulata) to genetically tractable chassis cells (e.g., Aspergillus oryzae). In addition, the oleaginous yeast Yarrowia lipolytica also plays a non-negligible role in the heterologous synthesis of polyunsaturated fatty acids. Starting from acetyl-CoA, filamentous fungi synthesize saturated fatty acids via the fatty acid synthase system and subsequently convert them to important PUFAs such as arachidonic acid (ARA), γ-linolenic acid (GLA), and eicosapentaenoic acid (EPA) through the sequential catalysis of Δ9-, Δ12-, Δ6-, and Δ5-desaturases and elongases. The SNF1 energy sensor, the nitrogen metabolism regulator AreA, and environmental factors constitute a complex multi-layer regulatory network that coordinately modulates fatty acid unsaturation and yield. The 2A peptide-based multigene co-expression platform, cofactor engineering, competitive pathway blockade, and fermentation process optimization have synergistically enabled the targeted accumulation of specific PUFAs. Nevertheless, industrialization of filamentous fungal PUFA production still faces major bottlenecks. We also provide a perspective on the industrial potential of filamentous fungi as “lipid cell factories” for the production of polyunsaturated fatty acids (PUFAs). This review aims to provide a comprehensive knowledge framework for researchers in related fields and to inform future fundamental research and industrial translation.