Oleaginous yeasts: Time to rethink the definition?

• Published in: Yeast (Chichester, England) England), 2022-11, Vol.39 (11-12), p.553-606
• Main Authors: Salvador López, José Manuel, Vandeputte, Meriam, Van Bogaert, Inge N. A.
• Format: Article
• Language: English
• Subjects: Adaptation; Biodegradation; Biotechnology; definition; Fatty Acids - metabolism; Fossil fuels; lipid; Lipids; Lipogenesis; Lipophilic; Oleaginous; Phenotypes; Saccharomyces cerevisiae - metabolism; Yarrowia - genetics; Yarrowia lipolytica; Yeast; Yeasts - genetics; Yeasts - metabolism
• ISSN: 0749-503X; 1097-0061
• DOI: 10.1002/yea.3827

Oleaginous yeasts are typically defined as those able to accumulate more than 20% of their cell dry weight as lipids or triacylglycerides. Research on these yeasts has increased lately fuelled by an interest to use biotechnology to produce lipids and oleochemicals that can substitute those coming from fossil fuels or offer sustainable alternatives to traditional extractions (e.g., palm oil). Some oleaginous yeasts are attracting attention both in research and industry, with Yarrowia lipolytica one of the best‐known and studied ones. Oleaginous yeasts can be found across several clades and different metabolic adaptations have been found, affecting not only fatty acid and neutral lipid synthesis, but also lipid particle stability and degradation. Recently, many novel oleaginous yeasts are being discovered, including oleaginous strains of the traditionally considered non‐oleaginous Saccharomyces cerevisiae. In the face of this boom, a closer analysis of the definition of “oleaginous yeast” reveals that this term has instrumental value for biotechnology, while it does not give information about distinct types of yeasts. Having this perspective in mind, we propose to expand the term “oleaginous yeast” to those able to produce either intracellular or extracellular lipids, not limited to triacylglycerides, in at least one growth condition (including ex novo lipid synthesis). Finally, a critical look at Y. lipolytica as a model for oleaginous yeasts shows that the term “oleaginous” should be reserved only for strains and not species and that in the case of Y. lipolytica, it is necessary to distinguish clearly between the lipophilic and oleaginous phenotype. Oleaginous yeasts are very promising for the production of biobased oleochemicals and many of them have been described. In this review, several of the limits for the definition of oleaginous yeast are discussed and analyzed to offer a more specific definition. Take‐away The term “oleaginous yeast” has mainly instrumental value for biotechnology. Oleaginicity is a property of strains, not species. Yeasts secreting lipids should also be considered oleaginous. Yeasts producing other lipids than TAGs should also be considered oleaginous. Yeasts showing oleaginicity in any condition should be considered oleaginous.