Diversity investigation of cultivable yeasts associated with honeycombs and identification of a novel Rhodotorula toruloides strain with the robust concomitant production of lipid and carotenoid.

[Display omitted] • Significant differences in cultivable yeast diversity between different honeycombs. • R. toruloides was isolated from honeybee-related products for the first time. • Lipid concentration and biomass reached 24.41 g/L and 36.78 g/L from 120 g/L glucose. • Biodiesel yield achieved as high as 93.15% from R. toruloides C23. • Transcriptome revealed hub genes involved in high biomass and high lipid production. Oleaginous yeasts-derived microbial lipids provide a promising alternative feedstock for the biodiesel industry. However, hyperosmotic stress caused by high sugar concentration during fermentation significantly prevents high cell density and productivity. Isolation of new robust osmophilic oleaginous species from specific environment possibly resolves this issue to some extent. In this study, the cultivable yeast composition of honeycombs was investigated. Totally, 11 species of honeycomb-associated cultivable yeast were identified and characterized. Among them, an osmophilic yeast strain, designated as Rhodotorula toruloides C23 was featured with excellent lipogenic and carotenogenic capacity and remarkable cell growth using glucose, xylose or glycerol as feedstock, with simultaneous production of 24.41 g/L of lipids and 15.50 mg/L of carotenoids from 120 g/L glucose in 6.7-L fermentation. Comparative transcriptomic analysis showed that C23 had evolved a dedicated molecular regulation mechanism to maintain their high simultaneous accumulation of intracellular lipids and carotenoids and cell growth under high sugar concentration. [ABSTRACT FROM AUTHOR]