With ever-increasing culture of yeasts for the production of biofuels and other metabolites, spent yeast
cell mass exceeds its traditional market demands. Yeast cell mass contains glucose, mannose and other
sugars that may be utilized for microbial culture. Here we demonstrated that the oleaginous yeast
Lipomyces starkeyi could utilize glucose and mannose simultaneously for lipid production. Overall
substrate consumption rates and lipid coefficients were 0.58 g/L/h and 0.18 g lipid/g sugar, respectively,
in flask cultures regardless of glucose, mannose or a mixture of both as the carbon source. L. starkeyi grew
well on the hydrolysates of spent cell mass of Rhodosporidium toruloides, consumed both glucose and
mannose therein, and produced lipid at a yield of 0.12 g lipid/g total reducing sugars. This co-utilization
strategy expands carbon sources for lipid production. It should provide an opportunity for recycling spent
cell mass and be of significant interests to biorefinery and biofuel production.