Technological Potential of Some Starch Degrading Yeasts

Abstract

AbstractThe possibility of obtaining lipids for alimentary or pharmaceutical use from starch degrading oleaginous yeasts was considered. The yeast strains, belonging to different species, were selected on the basis of two purposes: (a) microbial conversion of starch in fat material for human consumption; b) production of useful and rare single lipidic fractions such as phospholipids or unusual fatty acids. We worked with two groups of yeasts characterized by two patterns of lipid composition when grown on starch: one capable of accumulating high amounts of total lipids, up to 60–70% of dry weight, and the other capable of synthesizing a large amount of phospholipids. In the first group the phospholipids/triglycerides ratio was only slightly affected by the cultural conditions; in the second group this relationship was not only strongly influenced by the carbon/nitrogen ratio and nitrogen source but also by the rate of starch hydrolysis. In fact the amylase induction phase of the strains was found to be one of the most important factors determining the composition of the lipidic fraction. In the study of regulatory mechanisms controlling the synthesis of the phospholipids and triglycerides in the cells, mutants altered in the lipids biosynthesis and producing increased amounts of phospholipids were also employed.