Isolation, identification and screening of yeasts towards their ability to assimilate biodiesel‐derived crude glycerol: microbial production of polyols, endopolysaccharides and lipid

Abstract

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.

Direct transesterification of fatty acids produced by Fusarium solani for biodiesel production: effect of carbon and nitrogen on lipid accumulation in the fungal biomass

“…Glycerol is a byproduct of several industries and from biodiesel manufacture, so recyclation of glycerol as a carbon source for cultivation of our fungal strain as a source of lipid is a promising step. This was also confirmed with several other microbial strains (Meesters et al ; Filippousi et al ). Mortierella ramanniana presented a very interesting lipid production during growth on biodiesel‐derived glycerol (Papanikolaou et al ).…”

Lipid Production by Yeasts Growing on Commercial Xylose in Submerged Cultures with Process Water Being Partially Replaced by Olive Mill Wastewaters

“…Time (h) With the exception of the strain R. glutinis NRRL YB-252 that gradually and throughout the culture seemed to accumulate total intracellular polysaccharides (IPS) (in accordance with the results achieved during growth on glycerol under nitrogen-limited conditions; see Filippousi et al [40]), all other yeast strains used seemed to present higher IPS in TDCW values (Y IPS/X , % w/w) at the relative earlier growth steps, and these values seemed to decrease as growth proceeded. Moreover, in several of the tested microorganisms (i.e., strains C. curvatus NRRL Y-1511, R. toruloides NRRL Y-27012, R. toruloides DSM 4444, L. starkeyi DSM 70296), appreciable Y IPS/X quantities (i.e., ≥ 35% w/w) have been reported even at the very early growth steps (i.e., in fermentation time, t ≤ 60 h) where assimilable nitrogen was found into the medium-or it had barely been exhausted, in accordance with results in which other low-molecular weight hydrophilic carbon sources had been used as substrates under nitrogen-limited conditions (i.e., crude sucrose, lactose, biodiesel-derived glycerol, etc.…”

“…This result is in disagreement with recent investigations demonstrating the strain R. toruloides NRRL Y-27012 produced huge quantities of SCO (Y L/X > 40% w/w, in some trials this value was = 54.3% w/w, with an L max value ≈ 12 g/L) on media composed of crude glycerol, the principal waste stream deriving from biodiesel production process [39]. Equally, significant SCO quantities were produced by the strain R. glutinis NRRL YB-252 (Y L/X = 38.2% w/w, corresponding to L max ≈ 7.2 g/L) in similar types of media (crude glycerol) [40], demonstrating that in the above-mentioned yeast, as well as in a plethora of other yeast species and genera, glycerol is a very competitive substrate related with the production of TDCW and added-value extracellular and intracellular metabolites [33,[40][41][42][43]. It is not clearly understandable why such important discrepancies exist between the lipid production process for R. toruloides NRRL Y-27012 and R. glutinis NRRL YB-252 growing on xylose and glycerol, but in any case-and in accordance with the literature [4,5,22,23,44,45]-it appears that the carbon source seems to play a very crucial role in the de novo lipid production process, even if implicated substrates present important similarities among them in molecular and metabolic level.…”

“…Moreover, in several of the tested microorganisms (i.e., strains C. curvatus NRRL Y-1511, R. toruloides NRRL Y-27012, R. toruloides DSM 4444, L. starkeyi DSM 70296), appreciable Y IPS/X quantities (i.e., ≥ 35% w/w) have been reported even at the very early growth steps (i.e., in fermentation time, t ≤ 60 h) where assimilable nitrogen was found into the medium-or it had barely been exhausted, in accordance with results in which other low-molecular weight hydrophilic carbon sources had been used as substrates under nitrogen-limited conditions (i.e., crude sucrose, lactose, biodiesel-derived glycerol, etc. ; see: [33,40,47]). In contrast, in other yeast strains reported in the literature (yeast species/genera like Apiotrichum curvatum, Yarrowia lipolytica, other R. toruloides strains, Metschnikowia sp.)…”

Genomic Considerations for the Modification of Saccharomyces cerevisiae for Biofuel and Metabolite Biosynthesis

“…The native metabolic pathways in diverse microbes, including wild yeasts and bacteria, are particularly attractive for use in the production of biofuels via fermentation, which can generate bioethanol from a variety of non-food crop substrates, such as glycerol [3,4]. The metabolic flexibility of fungi allows for the generation of ethanol from materials (including olive mill wastewater) and the production of microbial enzymes and lipids from milling and confectioners' wastes [3,5,6].…”