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Background  Microbial lipids (triacylglycerols, TAG) have received large attention for a sustainable production of oleochemicals and biofuels.  Rhodosporidium toruloides  can accumulate lipids up to 70% of its cell mass under certain conditions. However, our understanding of lipid production in this yeast is still much limited, especially for growth with mixed substrates at the level of metabolic network. In this work, the potentials of several important carbon sources for TAG production in  R.toruloides  are first comparatively studied  in silico  by means of elementary mode analysis followed by experimental validation.    Results  A simplified metabolic network of  R.toruloides  was reconstructed based on a combination of genome and proteome annotations. Optimal metabolic space was studied using elementary mode analysis for growth on glycerol, glucose, xylose and arabinose or in mixtures. The  in silico  model predictions of growth and lipid production are in agreement with experimental results. Both the  in silico  and experimental studies revealed that glycerol is an attractive substrate for lipid synthesis in  R. toruloides  either alone or in blend with sugars. A lipid yield as high as 0.53 (C-mol TAG/C-mol) has been experimentally obtained for growth on glycerol, compared to a theoretical maximum of 0.63 (C-mol TAG/C-mol). The lipid yield on glucose is much lower (0.29 (experimental) vs. 0.58 (predicted) C-mol TAG/C-mol). The blend of glucose with glycerol decreased the lipid yield on substrate but can significantly increase the overall volumetric productivity. Experimental studies revealed catabolite repression of glycerol by the presence of glucose for the first time. Significant influence of oxygen concentration on the yield and composition of lipids were observed which have not been quantitatively studied before.    Conclusions  This study provides for the first time a simplified metabolic model of  R.toruloides  and its detailed  in silico  analysis for growth on different carbon sources for their potential of TAG synthesis. Experimental studies revealed the phenomenon of catabolite repression of glycerol by glucose and the importance of oxygen supply on the yield and composition of lipids. More systematic studies are needed to understand the mechanisms which should help to further optimize the lipid production in this strain of industrial interest.    Electronic supplementary material  The online version of this article (doi:10.1186/s12934-015-0217-5) contains supplementary material, which is available to authorized users.

Metabolic network analysis and experimental study of lipid production in Rhodosporidium toruloides grown on single and mixed substrates