Fig. 2

Metabolic pathway involved in xylitol production: In C. tropicals K2 (a diploid yeast), xylose enters the cell and is converted into xylitol by XYL1::XYL1 coding enzyme Xylose reductase (XR). A fraction of xylitol is secreted out of the cell, and most of the xylitol is further converted to xylulose by XYL2::XYL2 coding enzyme Xylitol dehydrogenase (XDH). Xylulose enters the PPP and supports cell growth and survival in the absence of glucose (left panel). In C. tropicalis K21D, a heterozygous for XYL2::xyl2Δ showed reduced XDH activity. Therefore, more xylitol is secreted out, and less xylitol is used for growth (left panel)