We have developed a novel approach, mimicking nutriment limitation, to trigger lipid accumulation and/or citrate production in vivo in the oleaginous yeast Yarrowia lipolytica. Strain JMY1203, containing a deletion of a mitochondrial gene, showed a partial block of the TCA cycle, resulted in a increase of citrate production which is redirected towards lipid production and the excess is secreted. In batch fermentation, the mutant strain JMY1203 produced less biomass and showed greater lipid accumulation and/or citrate production.
In the mutant strain, at 90g/L glycerol, biomass production was half that at 40g/L glycerol, and citrate production 1.87-fold higher. At this concentration, JMY1203 produced 57.7 g/L citric acid, 1.6-fold more than the wild-type strain, and the glycerol to citric acid conversion yield, 0.91 g/g, was the highest ever reported. This work demonstrates that lipid accumulation could be triggered by glycerol concentration and that a significant improvement in the glycerol to citrate conversion yield could be reached thought genetic engineering. This yield could be further improved by modification of the lipid synthesis and/or degradation pathway to favor either citrate production or lipid production.