Comparative Fatty Acid Compositional Profiles of <i>Rhodotorula toruloides</i> Haploid and Diploid Strains under Various Storage Conditions

Microbial-based fatty acids (FAs), biofuels and oleochemicals are potential alternatives to fossil fuels and other non-renewable resources. Rhodotorula toruloides (formerly Rhodosporidium toruloides) is a basidiomycetous oleaginous yeast, and cells of the wild-type diploids can accumulate lipids to over 70 wt% on a dry cell weight basis in nutrient-limited conditions. Meanwhile, several haploid strains have been applied as hosts for producing high-value fatty acid derivatives through genetic modification and metabolic engineering. However, the differences in fatty acid compositional profiles and their stability between diploid and haploid strains remain unknown in this oleaginous yeast. Here, we grew a haploid strain R. toruloides NP11 and its parental diploid strain R. toruloides CGMCC 2.1389 (4#) under identical conditions and compared the profiles in terms of cell growth, lipid production, fatty acid compositions of lipids as well as storage stability of fatty acid methyl esters (FAMEs). It was found that lipids from R. toruloides composed of fatty acids in terms of chain length ranged from short-chain FAs (C6–C9) to very long-chain FAs (VLCFAs, C20–C24) and some odd-chain FAs (C15 and C17), while long-chain fatty acids (C14–C18) were the most abundant ones. In addition, NP11 produced a little more (1 wt%) VLCFAs than that of the diploid strain 4#. Moreover, no major changes were found for FAMEs being held under varied storage conditions, suggesting that FAMEs samples were stable and robust for fatty acid compositional analysis of microbial lipids. This work revealed the fatty acid profiles of lipids from R. toruloides haploid and diploid strains, and their stability under various storage conditions. The information is valuable for reliable assessment of fatty acid compositions of lipids from oleaginous yeasts and related microbial cell factories