Morphological and metabolic shifts of Yarrowia lipolytica induced by alteration of the dissolved oxygen concentration in the growth environment

Abstract

Yarrowia lipolytica, an ascomycete with biotechnological potential, is able to form either yeast cells or hyphae and pseudohyphae in response to environmental conditions. This study shows that the morphology of Y. lipolytica, cultivated in batch cultures on hydrophilic (glucose and glycerol) and hydrophobic (olive oil) media, was not affected by the nature of the carbon source, nor by the nature or the concentration of the nitrogen source. By contrast, dissolved oxygen concentration (DOC) should be considered as the major factor affecting yeast morphology. Specifically, when growth occurred at low or zero DOC the mycelial and/or pseudomycelial forms predominated over the yeast form independently of the carbon and nitrogen sources used. Experimental data obtained from a continuous culture of Y. lipolytica on glycerol, being used as carbon and energy source, demonstrated that the mycelium-to-yeast form transition occurs when DOC increases from 0.1 to 1.5 mg l "1 . DOC also affected the yeast physiology, as the activity of enzymes implicated in lipid biosynthesis (i.e. ATP-citrate lyase, malic enzyme) was upregulated at high DOC whereas the activity of enzymes implicated in glycerol assimilation (such as glycerol dehydrogenase and kinase) remained fundamentally unaffected in the cell-free extract.

Regulation of amino-acid metabolism controls flux to lipid accumulation in Yarrowia lipolytica

“…Filamentation has been observed previously in bioreactor cultivations for studies of lipid accumulation. 15 Filamentation can be induced by a range of environmental changes, including the carbon source, 16,17 nitrogen source, 16,18,19 temperature, 20 oxygenation, 18,21 pH and buffer composition. 16,19 In addition, conflicting conclusions can be found in the literature, possible due to strain specificity.…”

Lipid accumulation in the new oleaginous yeast Debaryomyces etchellsii correlates with ascosporogenesis

“…Changes in cell length have been reported for S. cerevisiae grown in a chemostat under nitrogen limiting conditions at different dilution rates [45]. Mycelial forms were predominant during biomass production phase of Yarrowia lipolytica grown in bioreactor repeated batch cultures [46] and in a continuous bioreactor culture (working at 0.032 h À1 ) under low dissolved oxygen concentration (<0.13 mg L À1 ) [19].…”

Influence of environmental and nutritional conditions on yeast–mycelial dimorphic transition in Trichosporon cutaneum

“…Dimorphism is a peculiar characteristic of several yeast species and filamentous fungi, such as Candida albicans, Saccharomyces cerevisiae, Yarrowia lypolitica, Pichia fermentans, Schizosaccharomyces japonicus, Ustilago maydis, Ophiostoma floccosum, Ceratocystis ulmi, Mycosphaerella graminicola, which can switch between unicellular yeast and multicellular filamentous growth forms in response to changing environmental cues [1][2][3][4][5][6][7][8]. Usually, in the yeast stage, mitotic divisions either by budding or fission to produce two independent cells, while in the filamentous stage, cells become elongated yet fail to abscise following cytokinesis, and remain attached to form chains of elongated pseudohyphal cells; the true hyphae are produced with long continuous tubes and septae separating each of the nuclei in these tubes [2].…”