الفهرس 
Continuous culture selectionOnly 14 pages are availabe for public view
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Abstract
The present study was designed to obtain highly ethanol producing isolates of Saccharomyces cerevisiae via induced mutants and protoplast fusion techmques. The obtained results could be summarized as follows: Eleven different Saccharomyces strains were collected from National or International microbiology labs. Determination of their ethanol productivity was carried out. The diploid strain S. cerevisiae (No. 10) proved to be the highest producing one, more ethanol tolerant, and it was considered as the therrnotolerant strain in comparison with the other collected strains. Therefore, it was used in the following studies as the orignal strain. Generally, isolation of a haploid yeast from diploid yeast (No. 10) is an important protocol in order to study the effect of haploidization on ethanol productivity. Higher differences in ethanol productivity was found among haploid strains. Some of these haploid isolates (-No. 1,2, 4, 5, 9, 12, 14, 17 and 25) yielded nearly more ethanol than the original strain. Moreover, other haploids proved to produce the same or less ethanol than the original strain. Application of ultraviolet light as a mutagen with different exposure times followed by incubation in dark for two hours, led to the piclung of 1 6 1 isolates. The following results were obtained:3-a- The survival percentage decreased gradually whle exposure time increased. 3-b- The hghest number of auxotrophs was obtained following 15 min. exposure time, whde hgher morphological variations were noticed after 10 min. exposwe time.