Oleaginous yeasts: Time to rethink the definition?

Abstract

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 nonoleaginous 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"

Insights into the Genomic and Phenotypic Landscape of the Oleaginous Yeast Yarrowia lipolytica

“…Similarly, for lipid accumulation, i.e., with oleic acid and glucose as carbon sources, we observed a huge variation with lipid content reaching up to 73.6% DCW in strain CBS 6125, a strain isolated from a maize-processing plant. This level of lipid content had never been reported so far for a wild strain; Y. lipolytica is known to usually store around 40–45% of its DCW at most [ 2 ]. One exception is the study of Bati et al, who reported a 70.7% lipid content in strain NRRL Y-1094 grown on 18 g/L corn oil [ 77 ].…”

“…From a fundamental perspective, the species is mainly used to better understand lipid uptake, synthesis, degradation, and storage. Indeed, some strains are able to accumulate more than 20% of their dry cell weight as lipids, thus defining them as oleaginous yeasts [ 2 ]. From a biotechnological point of view, Y. lipolytica is used in a wide range of industrial applications, especially in the oleochemical industry, to synthesize bioplastics and biofuels from low-value substrates generated from industrial or agricultural wastes [ 3 , 4 , 5 ].…”

“…Although Y. lipolytica is extensively studied for its metabolic properties, little is known about the genetic and phenotypic diversity of the species. The most studied trait has been the capacity for lipid synthesis and accumulation [ 2 , 26 ]. A few recent studies used other phenotypic screenings to select promising strains for particular applications, some of which tried to correlate phenotypes and genotypes.…”

Natural trait variation across Saccharomycotina species

“…Many variable traits that do not meet this description are of keen ecological and applied interest in Saccharomycotina , e.g. salt, heat, and cold tolerance (Robert et al 2015 , Gostinčar and Gunde-Cimerman 2018 , Segal-Kischinevzky et al 2022 ); drug sensitivity (Kuo et al 2010 ); DNA damage response (Milo et al 2019 , Steenwyk et al 2019 , Shor et al 2020 , Steenwyk 2021 ); riboflavin production (Averianova et al 2020 ); and the oleaginous phenotype (Ratledge 2013 , He et al 2018 , Abeln and Chuck 2021 , Salvador López et al 2022 ). As we often need specialized phylogenetic methods to infer when and why evolution has built a given quantitative trait, these cases tend to form a topic all to themselves and are not our focus here.…”

lista-GEM: the genome-scale metabolic reconstruction ofLipomyces starkeyi

“…The optimization of bioprocesses allied with advances in genetic and metabolic engineering have enabled considerable advances in the production of lipids using oleaginous yeasts. These yeasts can accumulate at least 20% of their dry biomass as lipids, especially triacylglycerols (TAGs) (Salvador López et al, 2022). The requirement for sustainable sources of lipids for the production of oleochemicals, biodiesel, and human nutrition has boosted research with oleaginous yeasts able to use agricultural, industrial, and urban wastes as substrates for the development of bioprocesses (Abeln and Chuck, 2021; Spagnuolo et al, 2019).…”