Hosni Sassi was from Free University of Brussels, Belgium


The non-conventional yeast Yarrowia lipolyticahas received much attention as a potential host for heterologous protein production with both academic and commercial applications.To this end, the selection of strong and tightly regulated promoters together with the optimisation of heterologous gene expression is essential for the production of pharmaceucals at industrial scale. Hight heterologous protein production in response of carbon source uptake is of great interest. In this work, the promoter of acycl-CoA oxidase gene 2 (pPOX2) was studied in regard with its regulation during cell growth on complex and defined medium supplemented with different carbon sources.Throught a different combinations of carbone sources, we aimed to define and select the best medium and carbon source for hight level of heterologous protein expression in this yeast. For this purpose, pPOX2 was fused with a reporter gene coding for a red fluorescence protein (DsRed).Measurement of normalized fluorescence level revealed thatpPOX2 is strongly induced during growth on medium containing oleic acid as sole carbon source or in combination with glucose or glycerol. Moreover, complex medium appears as the most preferred one. Nevertheless, this promoter is repressed when glucose or glycerol were using as the sole carbon source. This result suggests that oleic acid is a very strong inducer of pPOX2. Furthermore, the useof glycerol in combinationwith oleic acid let to the same amount of fluorescence levelinboth complex and defined medium. Thisresearch elucidates the effect of different carbon source on gene expression under pPOX2control. Indeed,the use of glycerol as carbon source offers not only a low cost bioprocess but it also open new perspectives for glycerol based microbiological processes. This work provides an alternative strategy to maximize heterologous protein production in Y. lipolyticawith the consequence of an increased interest in this yeast as a host for heterologous protein production.