Cultures were performed in MY supplemented with 0.01 g l−1 ergosterol and 0.42 g l−1 Tween 80 dissolved in ethanol, silicon antifoam, vitamin solution and trace elements [7], and 20 g l−1 glucose (MYG) or arabinose (MYA).

Intracellular metabolic fluxes were calculated through metabolic flux balancing using a compartmented stoichiometric model that was previously developed for describing aerobic growth on glucose [1,2] and modified to describe anaerobic growth on glucose and arabinose. Reactio ... ns required for production and excretion of organic acids and for transport of oleate and palmitoleate (required for lipid biosynthesis) and the fumarate reductase reaction (TCA reductive branch) were introduced [1, 3]. Four reactions necessary for arabinose utilization were added to the model: arabinose transport, arabinose isomerase, l-ribulokinase and l-ribulose-5-phosphate-4-epimerase. The assumed macromolecular biomass composition was 45% (w/w) protein, 40.7% (w/w) polysaccharides, 6.3% (w/w) RNA, 0.4% (w/w) DNA, 2.9% (w/w) lipid, 2.5% (w/w) metals, 1.2% (w/w) water, 0.8% (w/w) phosphate and 0.2% (w/w) sulfate [2, 4]. Measured protein contents of IMS0001 and IMS0002 strains agreed with the assumed value (data not shown). Dedicated software (SPAD it, Nijmegen, The Netherlands) was used for metabolic flux balancing, the theory and practice of which have been thoroughly described elsewhere (4, 5, 6) and will not be repeated here. For each growth condition, specific rates of growth, substrate consumption and carbon-dioxide, glycerol, acetate, pyruvate, lactate and succinate production were measured. For the conversion of fluxes into mmoles per Cmole of biomass, a biomass C-molar weight of 25.87 g mol−1 was used [2, 4]. The number of measured rates was sufficient to result in an over-determined system, thus enabling data reconciliation. In all cases the degree of redundancy equaled 2. --------------------------------------------References---------------------------------------
[1] P. Daran-Lapujade, M.L. Jansen, J.M. Daran, W. van Gulik, J.H. de Winde, J.T. Pronk. J. Biol. Chem., 279 (2004), pp. 9125-9138. http://doi.org/dhhj2k
[2] Lange, H.C., 2002. Quantitative physiology of S. cerevisiae using metabolic network analysis. Ph.D. Thesis, Delft University of Technology, Department of Biotechnology, the Netherlands.
[3] K. Enomoto, Y. Arikawa, H. Muratsubaki. FEMS Microbiol. Lett., 215 (2002), pp. 103-108. http://doi.org/c6x6g6
[4] T.L. Nissen, U. Schulze, J. Nielsen, J. Villadsen.Microbiology, 143 (1997), pp. 203-218. http://doi.org/dwvx2q
[5] Vallino, J.J., Stephanopoulos, G., 1990. In: S.K. Skidar, M. Bier, P. Todd (Eds.), Frontiers in Bioprocess. CRC Press, Boca Raton, FL, pp. 205–219.
[6] W.M. van Gulik, J.J. Heijnen. Biotechnol. Bioeng., 48 (1995), pp. 681-698. http://doi.org/fsv4g6