Two alternative pathways for substrate assimilation by Mucor circinelloides

Transition of an oleaginous strain of Mucor circinelloides from mycelial to yeast-like form was studied in conditions favoring lipogenesis. In culture media with citric acid as the sole carbon source at concentrations of 7.5 and 10 g/L (C/N ratio of 26 and 35, respectively), the mold accumulated significant quantities of lipid. At a higher citric acid concentration liposynthesis was inhibited and the fermentation mechanism decreased the high substrate concentration in the culture media. Under these conditions yeast-like morphogenesis was observed. In the yeast-like cells, biosynthesis of linoleic and gamma-linolenic acid was inhibited. In contrast, no significant changes were observed in the biosynthesis of palmitoleic acid whereas the concentration of oleic acid was increased in the storage lipids of yeast-like cells.