Abstract
We previously developed a fermentation protocol for lipid accumulation in the oleaginous yeast Y. lipolytica. This process was used to perform transcriptomic time-course analyses to explore gene expression in Y. lipolytica during the transition from biomass production to lipid accumulation. In this experiment, a biomass concentration of 54.6 gCDW/l, with 0.18 g/gCDW lipid was obtained in ca. 32 h, with low citric acid production. A transcriptomic profiling was performed on 11 samples throughout the fermentation. Through statistical analyses, 569 genes were highlighted as differentially expressed at one point during the time course of the experiment. These genes were classified into 9 clusters, according to their expression profiles. The combination of macroscopic and transcriptomic profiles highlighted 4 major steps in the culture: (i) a growth phase, (ii) a transition phase, (iii) an early lipid accumulation phase, characterized by an increase in nitrogen metabolism, together with strong repression of protein production and activity; (iv) a late lipid accumulation phase, characterized by the rerouting of carbon fluxes within cells. This study explores the potential of Y. lipolytica as an alternative oil producer, by identifying, at the transcriptomic level, the genes potentially involved in the metabolism of oleaginous species.
Highlights
In a context of increasing concern about global warming and dwindling stocks of fossil fuels, the search for alternative, renewable sources of energy is a matter of the utmost importance for modern societies
The initiation of lipid accumulation during lipid synthesis is caused by the exhaustion of a primary nutrient from the culture medium
The catalytic growth rate slows down rapidly, whereas the rate of carbon assimilation slows more gradually [7,37]. This results in the preferential channelling of carbon flux toward lipid synthesis, leading to an accumulation of triacylglycerols within the lipid body of the cell
Summary
In a context of increasing concern about global warming and dwindling stocks of fossil fuels, the search for alternative, renewable sources of energy is a matter of the utmost importance for modern societies. Biodiesel has rapidly become one of the most promising and widely studied alternative sources of energy. Biodiesel is produced from refined or edible oils using methanol and an alkaline catalyst. The large-scale production of biodiesel requires considerable amounts of these oils, resulting in a sharp increase of their demand over the last decade. The eventual goal is to gain access to a sustainable energy source, as traditional methods of obtaining oils from plants have raised unexpected ecological and sociological issues (e.g. extensive use of arable land, replacement of food crops with fat-producing crops for biofuel production). The development of new production procedures from non-edible oils appears to be an essential prerequisite for a sustainable biodiesel industry. Several esterification processes are currently developed for the utilization of these oils, often containing free fatty acids (FFA)
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