Lipids of yeasts and filamentous fungi and their importance for biotechnology

Abstract

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 by a variety of complex biochemical reactions. Lipids consist of highly reduced molecules, and the redox factor providing electrons for their synthesis is NADPH, which is mainly produced by the pentose phosphate pathway and malic enzyme. There are a variety of fungi that can accumulate lipids; oleaginous fungi can accumulate 20 to more than 80% of their biomass as lipids. Many of them can convert carbon sources derived from second-generation substrates or low-value residues, such as lignocellulose hydrolysate or crude glycerol from biodiesel production. There are also substantial efforts to genetically manipulate fungi to produce lipids or lipid-derived compounds with high-efficiency and from low-value substrates. Lipids have broad potential in biotechnological applications. Polyunsaturated fatty acids are essential for human nutrition, and they can be produced in high amounts by certain zygomycetous species or by genetically modified yeasts. Acylglycerides can be converted to 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 the target for developing novel antifungal drugs. As most lipids are stored intracellularly, there is also a high demand for process development towards a sustainable production of lipid-derived fuels and chemicals. Lipid metabolism of fungi and its biotechnological utilisation has recently obtained huge attention and is a rapidly developing field.