الفهرس 
3MATERIALS AND METHODSOnly 14 pages are availabe for public view
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Abstract
The selected commercial yeast cultures Saccharomyces boulardii (SB1 and SB2) were identified by determining the sequence of rDNA of the ITS region for two isolated yeasts then a database search for similar sequences in the GenBank was performed using the BLASTn program. The commercial and pure yeast cultures were preserved by chilled, freezing, and drying methods. According to the obtained results, preserving the yeast cultures by freezing technique is considered the more suitable method for yeast preservation. Encapsulation technique was applied on yeast cultures before the lyophilization process to enhance the viability of lyophilized yeast cells.
Yeast cultures were subjected to probiotic microbial selection experiments. Tolerance to pH, bile salt, temperature, simulated gastrointestinal conditions in vitro, antibiotics, auto-aggregation capacity, cell surface hydrophobicity, ability to assimilate cholesterol, anticancer activity, antimicrobial activity, and antioxidant activity are the selection experiments which carried out to decide if the examined yeast strains can be considered as probiotic microorganisms.
from the obtained results, Saccharomyces boulardii SB1 and SB2 strains achieve the highest scores in most carried out experiments to be considered as a probiotic strains. The addition of prebiotics (inulin and lactulose) increased the viability of yeast strains under study with the increase of addition level up to 5% in particular with the strains SB1 and SB2 yeast cultures.
The tested yeast strains were used for the production of gummy candy and sweet potato puree with the addition of inulin or lactulose to the recipe of each product. The gummy candy supplemented with the strains SB1 and SB2 remained intact without the growth of fungi until the end of the storage period. In concern with texture profile, no remarkable effects of yeast strains on cohesiveness and springiness were observed for the tested candy samples. The addition of S. boulardii yeast with suggested prebiotic material had a positive effect on most sensory properties of sweet potato puree.