Physiological factors affecting total cell number and lipid content of the yeast, Lipomyces starkeyi.

Abstract

The effects of the concentration of the medium components and other cultural conditions on the total cell number and on the lipid content (mg of total lipid/108 cells) of the fat yeast L. starkeyi were examined. The no addition and deficiency of NH4+, K+, Mg2+, PO43-, SO42-, Zn2+, Fe2+ or Mn2+ decreased the total cell number. Mn2+ sufficiency increased the total cell number by a factor of 1.5 to 1.7, as compared with that of the standard concentration. The lipid content of the yeast was affected by 6 (NH4+, K+, Ca2+, Zn2+, Fe3+ and Mn2+) ion concentrations. The no addition and deficiency of Zn2+ increased the lipid content by a factor ranging from 2.4-2.8 in comparison with that of the standard concentration. The concentration of Zn2+ also altered the lipid yield (g of lipid/100 g of glucose consumed) considerably. The concentration of Na+, Cl-, Cu2+, BO33-, I-, MoO42- and biotin had almost no effect on the total cell number, lipid content and lipid yield of L. starkeyi. The cultural temperature and the initial pH value of the medium affected the total cell number and lipid content; the optimum temperature ranged from 25.5-29.5.degree. C and the optimum pH value was 4.9. A low concentration of dissolved O2 decreased both the total cell number and lipid content. D-Glucose, D-mannose, D-galactose, D-levulose, sucrose, D-xylose and L-arabinose proved to be usable C sources for the growth and the lipid accumulation of L. starkeyi.