الفهرس 
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Abstract
In 1949 Boris Ephrussi (Cited from Bernardi, 1979) gave the first account of investigations on the petite colonie mutation in Saccharomyces cerevisiae which was distinctly smaller colonies. The appearance of these colonies between the plated cells suggested that the population of cells was heterogeneous. Acriflavine treatment increases the number of petite mutants which grow slowly because they cannot respire, owing to the loss of their ability to synthesize a whole series of respiratory enzymes. Ephrussi concluded that wild type cells and petite mutants were differed by the presence in the former and the absence in the latter of cytoplasmic units required for the synthesis of certain respiratory enzymes. These units identified as mitochondrial genes 20 years later. These findings established that the structure of mitochondrial DNA was differed between wild type cells and respiratory deficient mutants. Saccharomyces cerevisiae used for bread manufacturing which can convert the fermentable sugars containing dough into carbon dioxide and ethanol as the main products. The fermentation intensity depends on the yeast genotype and the availability of fermentable sugars containing flour, including maltose produced from hydrolysis of starch. The wheat flour comprised of approximately 71% carbohydrates of which the vast majority is starch, 13% protein, 1% lipid and 14% water. During fermentation, no new bubbles are created, but only the volume of bubbles already in the dough can be increased due to the production of CO2 thereby increasing the volume of dough. Bread industry has a very important place in the food manufacturing sector and is in full process of expansion and automation. One of the most significant current studies in dough fermentation is survivability and bioactivity of Saccharomyces cerevisiae. However, wheat flour is the main ingredient in most types of breads, when it was mixed with water gluten as a complex protein was formed. The gluten gives wheat dough an elastic structure. In this study two samples of instant dry yeast were used to isolate the commercial strain of Saccharomyces cerevisiae. Both yeast strains isolated in this study were subjected to different acriflavine concentrations to be evaluated respiratory deficient mutants induced for their fermentation process of bread dough prepared from wheat flour. In this study kinetin and naphthyl acetic acid were used as a plant growth hormones to compare their effects with a mutagenic agent acriflavine on the extra chromosomal genome of Saccharomyces cerevisiae. Kinetin was used with the following concentrations; 0, 2, 4, 6, and 8 ppm. Meanwhile, naphthyl acetic acid was used with the following concentrations; 0, 20, 40, 60, and 80 ppm. Furthermore, acriflavine was used with the following concentrations; 0, 1, 2, 3, and 4 ppm. This study intended to investigate the comparison of characteristics between respiratory deficient mutants and their wild type strain for fermentation ability of dough. The results obtained from this work were summarized as follows: 1. Acriflavine treatments showed significant toxicity on the viability of yeast cells via a dose – response appeared. 2. At the concentration of 1 ppm the parental cells of isolate A retain the normal respiratory abilities, while the isolate B was less produced petite mutants. 3. High rate of petite mutants was obtained when the cells were exposed to 4 ppm. 4. Isolate B was more sensitive to acriflavine than isolate A regarding the decline in the viability of cells and respiratory deficient mutants induced. 5. Kinetin and naphthyl acetic acid showed a dose – response for the viability of yeast cells without respiratory deficient mutants induced. 6. Both plant growth hormones enhances the division of yeast cells leading the cells to continue growing. 7. Plant growth hormones plays several vital roles in biochemical processes related to cell cycle of yeast cells. 8. The signaling molecules regulated cell growth must received significant attention because it is alarm sounds for the potential of carcinogenicity. 9. The turbidity of most grand isolates and all respiratory deficient mutants were significantly decreased if compared with the wild-type strain. 10. The time of fermentation was increased by all isolates resulted from acriflavine treatments such grand or petite mutants in relation to the wild-type strain which will be non-acceptable in the production of bread. 11. Non-of the isolates derived from acriflavine treatments such grand or petite mutants exhausted higher scores of carbon dioxide production than the wild-type strain. 12. The wild-type strain was excellent than the isolates derived from acriflavine in the ability of carbon dioxide production leading it superior for bread industry than biochemical mutants. 13. The height quantities of carbon dioxide released was registered by the wild-type strain followed by grand cells and petite mutants.