EFFECT OF OSMOTIC POTENTIAL OF SUGARS ON THE BIOLOGICAL ACTIVITY OF YEAST

Abstract

This investigation was primarily targetted towards in­ vestigating the biological activity of osmophilic yeasts isolated from some Egyptian foodstuffs. The objectives of this study were:

I. Isolation of osmophilic yeasts and their identification. 2. Selection of some osmophilic yeasts according to their abil­ ity to ferment and assimilate sugars. 3. Propagation of these yeasts in shake flasks as a batch proc­ ess in the presence of different concentrations of glucose, sucrose and sodium chloride. 4. Fermentation products (ethanol and glycerol) and reserved cell materials (glycogen, trehalose) as influenced by sugar and salt concentrations. 5. Effect of osmotic pressure of sugars on the activity of alco­ hol dehydrogenase and invertase as well as oxygen con­ sumption rate.

Results could be summarized as follows:- !. Thirty nine osmophilic yeasts were isolated from different nine sources of foodstuffs. According to the morphological and physiological .properties of these yeasts, it was found that 64.1% were belonged to the genus Tornlopsis, 25.6% belonged to the genus Saccharomyces, 1.1% belonged to the genus Candida and 2.6% belonged to the genus Rhodo­ tornla. 2. Three yeast species were selected, Saccharomyces kluyveri G29 (highly fermentative), Saccharomyces cerevisiae S41 (moderately fermentative) and Rhodotornla mucilaginosa J38 (an oxidative yeast) to study their biological activities.