Lipids of Yeasts and Filamentous Fungi and Their Importance to Biotechnology

Lipids are essential for any organism. They are hydrophobic compounds and include, for instance, acylglycerides, free fatty acids, sterols, and isoprenoids. Their synthesis starts from acetyl-CoA, which is converted to lipids through a variety of complex biochemical reactions. Lipids consist of highly reduced molecules, and the redox factor providing electrons for their synthesis is NADPH, mainly produced by the pentose-phosphate pathway and the malic enzyme. Various fungi can accumulate lipids, with oleaginous fungi capable of accumulating 20 to more than 80% of their biomass as lipids. Many of these fungi can convert carbon sources derived from second-generation substrates or low-value residues, such as lignocellulose hydrolysate, volatile fatty acids, or crude glycerol from biodiesel production. There are also substantial efforts to genetically manipulate fungi to produce lipids or lipid-derived compounds efficiently from low-value substrates. Lipids have broad potential in biotechnological applications. Polyunsaturated fatty acids are essential for human nutrition and can be produced in high amounts by certain zygomycetous species or genetically modified yeasts. Acylglycerides are not only the primary components of edible oils but can also be converted into biodiesel and high-value chemicals. It is possible to obtain biodiesel, jet fuel, specific chemicals and carotenes as chemicals and food and feed additives from isoprenoids. Lipids can be combined with other biomolecules. Glycolipids have a high biotechnological potential as biosurfactants. Lipoproteins are essential for the viability of any eukaryotic cell and can be targets for developing novel antifungal drugs. As most lipids are stored intracellularly, there is a high demand for process development towards sustainable production of lipid-derived fuels and chemicals. The lipid metabolism of fungi and its biotechnological utilisation has recently gained significant attention and is a rapidly developing field.