A total of 11 yeast strains of Yarrowia lipolytica, Metschnikowia sp., Rhodotorula sp. and Rhodosporidium toruloides were grown under nitrogen-limited conditions with crude glycerol employed as substrate in shake flasks, presenting interesting dry cell weight (DCW) production. Three of these strains belonging to Metschnikowia sp. accumulated significant quantities of endopolysaccharides (i.e. the strain V.V.-D4 produced 11.0 g/L of endopolysaccharides, with polysaccharides in DCW ≈ 63% w/w). A total of six Y. lipolytica strains produced either citric acid or mannitol. Most of the screened yeasts presented somehow elevated lipid and polysaccharides in DCW values at the early steps of growth despite nitrogen appearance in the fermentation medium. Lipid in DCW values decreased as growth proceeded. R. toruloides DSM 4444 cultivated on media presenting higher glycerol concentrations presented interesting lipid-accumulating capacities (maximum lipid = 12.5 g/L, maximum lipid in DCW = 43.0–46.0% w/w, conversion yield on glycerol = 0.16 g/g). Replacement of crude glycerol by xylose resulted in somehow decreased lipid accumulation. In xylose/glycerol mixtures, xylose was more rapidly assimilated from glycerol. R. toruloides total lipids were mainly composed of triacylglycerols. Total cellular fatty acid composition on xylose presented some differences compared with that on glycerol. Cellular lipids contained mainly oleic and palmitic acid.

Aims To assess the ability of various newly isolated or belonging in official collections yeast strains to convert biodiesel‐derived glycerol (Gly) into added‐value compounds. Methods and Results Ten newly isolated yeast strains belonging to Debaryomyces sp., Naganishia uzbekistanensis, Rhodotorula sp. and Yarrowia lipolytica, isolated from fishes, metabolized Gly under nitrogen limitation. The aim of the study was to identify potential newly isolated microbial candidates that could produce single‐cell oil (SCO), endopolysaccharides and polyols when these micro‐organisms were grown on biodiesel‐derived Gly. As controls producing SCO and endopolysaccharides were the strains Rhodotorula glutinis NRRL YB‐252 and Cryptococcus curvatus NRRL Y‐1511. At initial Gly (Gly0) ≈40 g l−1, most strains presented remarkable dry cell weight (DCW) production, whereas Y. lipolytica and Debaryomyces sp. produced non‐negligible quantities of mannitol and arabitol (Ara). Five strains were further cultivated at increasing Gly0 concentrations. Rhodotorula glutinis NRRL YB‐252 produced 7·2 g l−1 of lipid (lipid in DCW value ≈38% w/w), whereas Debaryomyces sp. FMCC Y69 in batch‐bioreactor experiment with Gly0 ≈80 g l−1, produced 30–33 g l−1 of DCW and ~30 g l−1 of Ara. At shake‐flasks with Gly0 ≈125 g l−1, Ara of ~48 g l−1 (conversion yield of polyol on Gly consumed ≈0·62 g g−1) was achieved. Cellular lipids of all yeasts contained in variable concentrations oleic, palmitic, stearic and linoleic acids. Conclusions Newly isolated, food‐derived and non‐previously studied yeast isolates converted biodiesel‐derived Gly into several added‐value metabolites. Significance and Impact of the Study Alternative ways of crude Gly valorization through yeast fermentations were provided and added‐value compounds were synthesized.

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