Modulation of the Glycerol Phosphate availability led to concomitant reduction in the citric acid excretion and increase in lipid content and yield in Yarrowia lipolytica
Sagnak, Rana | Cochot, Sandrine | Molina-Jouve, Carole | Nicaud, Jean-Marc | Guillouet, Stéphane E.
In order to improve TriAcylGycerol (TAG) lipids accumulation in the yeast Yarrowia lipolytica on glucose, double over-expression of the major acyl-CoA:diacylglycerol acyltransferase encoding gene (ylDGA2) and of the glycerol-phosphate dehydrogenase encoding gene (ylGPD1) was carried out. The genes were over-expressed in a strain impaired for the mobilization of the accumulated lipids, through the deletion of the genes encoding acyl-coenzyme A oxidases (POX1-6 genes) and the deletion of the very efficient lipase attached to the lipid bodies, encoded by ylTGL4. This metabolic engineering strategy had the objective of pulling the C-flow into the TAG synthesis by increasing the availability of glycerol-3-phosphate and its binding to fatty acids for the TAG synthesis.This strain showed a strong improvement in production performances on glucose in terms of lipid content (increase from 18 to 55%), lipid yield (increase from 0,035 to 0.14gg −1) and by-product formation (decrease in citric acid yield from 0.68 to 0.4gg −1).For developing bioprocess for the production of triacylglycerol from renewable carbon sources as glucose it is of first importance to control the C/N ratio in order to avoid citric acid excretion during lipid accumulation. Our engineered strain showed a delay in the onset of citric acid excretion as suggested by the 15% modulation of the critical C/N ratio.
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