Cell mass energetic yields of fed-batch culture by Lipomyces starkeyi.

Estimation of the energy capacity of a microbial cell mass on the basis of its lipid content and elemental composition can be used for the comparative evaluation of different microbial sources of biodiesel. Lipomyces starkeyi cell mass concentration reached 94.6 g/L with 37.4% of lipids in a fed-batch process using xylose and urea as substrates. The fatty acid composition of the yeast oil was quite similar to that of palm oil. L. starkeyi converted more than 80% of the energy contained in xylose into cell mass energy yield. The approach used in this study makes it possible to determine the energy of a cell mass by its elemental composition. A heat of combustion (Q c) of 25.7 (kJ/g) was obtained for the cell mass after 142 h of fed-batch cultivation, which represents approximately 56% of the energy content of diesel oil (45.4 kJ/g). The Q c of the triacylglycerols produced was 48.9 (kJ/g), indicating the potential of this oleaginous yeast for biodiesel production. Our work developed here provides a simple and efficient tool for characterization of this cell mass to further our understanding of its use as a feedstock for bioenergy production.