الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
Seventy eight yeasts were isolated from different foodstuffs. This yeasts belonged to genera of Candida,
I
Geotrichum, Hansenula, Kloeckera, Rhodotorula,
Schizoblastosporion and Trichosporon represented 74.4%,
3.8%, 2.6%, 6.4%, 8.8%, 2.6% and 1.3% respectively.
Four yeast species namely C. parapsilosis Q3, C. solani F8, C. versatilis J3 and K. jensenii H1 were selected to study their biological activity. At 1 and 10% glucose, C. parapsilosis Q3 showed the highest growth being 0.18 x 10 and 0.55 x 10 optical density respectively. At 5% NaCl the four strains can grow except C. so/ani F8 which its biomass decreased. In addition, only C. versatilis 13, could assimilated nitrate and exhibited higher growth (0.54 x 10 optical density) compared with other yeasts. On the other hand, C. solani F8 showed amylolytic activity (85.8 Nulrnl) after 48 hours of incubation in media containing 2% starch, while all strains except C. versatilis J3 showed a proteolytic activity being 40, 34, 25 unit
I ml for C. so/ani F8, C. parapsilosis Q3 and K. jensenii Hl,
respectively. Both of C. versatilis J3 and K. jensenii Hl grew well at 35°C while C. so/ani F8 and C. parapsilosis Q3 grew well at 30 and 20°C respectively. The optimum pH for yeast growth was recorded at pH 5 for C. versatilis 13, C. parapsilosis Q3 and at (4 to 7) for C. so/ani F8, and K. jensenii Hl. The viability of the tested strains was highly affected by frozen storage. Yeast can grow in the presence of low concentration of lactic, acetic and citric acids. Ethanol up to 5% was utilized by C. versatilis J3 and up to 4% by other strains. Garlic and onion out of many spices inhibited the selected four yeast strains. NaCl at 5%, 10% inhibited the fermentation power of yeast strains. Besides, consumed sugar for C. versatilis J3, C. parapsilosis Q3 reached to its maximum on the 12th hours of incubation while both of C. solani FS and K. jensenii HI showed the same trend on 24th hours. The four selected yeast strains exhibited an antagonistic effect againts different microorganisms. C. solani FS had the highest affmity for glucose followed by K. jensenii HI, C. versatilis J3 and C. parapsilosis Q3.