2019 Donzella MICF
Engineering cytoplasmic acetyl-CoA synthesis decouples lipid production from nitrogen starvation in the oleaginous yeast Rhodosporidium azoricum
Donzella S., Cucchetti D., Capusoni C., Rizzi A., Galafassi S., Gambaro C., Compagno C.
Oleaginous yeasts are able to accumulate very high levels of neutral lipids especially under condition of excess of Carbon and Nitrogen limitation (medium with high C/N ratio). This makes necessary the use of two-steps processes in order to achieve high level of biomass and lipid. To simplify the process, the decoupling of lipid synthesis from nitrogen starvation, by establishing a cytosolic Acetyl-CoA formation pathway alternative to the one catalysed by ATP-citrate lyase, can be useful.
In this work, we introduced a new cytoplasmic route for acetyl-CoA (AcCoA) formation in Rhodosporidium azoricum by overexpressing genes encoding for homologous phosphoketolase (Xfpk) and heterologous (from B. subtilis) phosphotransacetylase (Pta). In a bioreactor process performed on glucose/xylose mixture, to simulate an industrial process for lipid production from lignocellulosic wastes, we obtained an increase of 89% in final lipid concentration by the engineered strain in comparison to the wild type, even by feeding nitrogen during the process. Our results indicate that the introduction of a new cytosolic AcCoA supply decouples lipid production from nitrogen starvation in R. azoricum. This metabolic modification allows improving lipid production in cultural conditions that can be suitable for the development of industrial bioprocesses using lignocellulosic hydrolysates.
