MCB 180 Yeast

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MCB 180 Yeast
   Yeasts are fungi that grow as single cells, producing daughter cells either by budding (the budding yeasts ) or by binary fission (the fission yeasts ). They differ from most fungi, which grow as thread-like hyphae. But this distinction is not a fundamental one, because some fungi can alternate between a yeast phase and a hyphal phase, depending on environmental conditions. Such fungi are termed dimorphic (with two shapes) and they include several that cause disease of humans. accharomyces cerevisiae is the budding yeast used for bread-making, where the carbon dioxide produced by growth in the dough causes the bread to rise. Essentially similar yeasts, but now given different species names, are used for production of beers, wines and other alcoholic drinks. This phase-contrast micrograph shows cells in various stages of budding. The buds are small at first, but enlarge progressively and eventually separate from the mother cell by formation of a septum  (cross wall). Few of the cellular organelles can be seen by light microscopy, unless they are stained specifically. The only conspicuous organelle seen in Fig. A is the large central vacuole  which contributes to cell expansion. S. cerevisiae   is a member of the fungal group scomycota  (the ascus-forming fungi). Beneficial Uses of Yeast: 1. Bread-making  –   for the manufacture of bread, yeast is mixed with white flour. The process of fermentation starts. The bread swells up and becomes spongy due to the pressure exerted by accumulated carbon dioxide. 2. Source of food  –   yeasts contains nutritive substances and proteins in sufficient quantities. 3. Source of Vitamins  –   with ultra-violet rays, they produce Vitamin D. 4. Used in Brewing Industry  –   yeast is added to malted grains and allowed to ferment.  Yeasts are usually present on the skin of grapes and can be used to naturally ferment grape  juice into wine. 5. Nutrition  –   good source of protein, Vitamin B and minerals. 6. Used in Medicine  –   lowers high cholesterol and triglyceride levels caused by human immunodeficiency virus disease (AIDS). They are also utilized in medicine as a source of enzymes. 7. Research  –   traditional biotechnology, used in biofuel industry to produce ethanol.  8. Molecular Genetics  –   model organisms in genetics, used as synthetic pathways for antibiotics and used in gene therapy. 9. Bioremediation Disadvantageous Uses of Yeasts: 1. Food Spoilage  –   yeasts metabolize some food components and produce metabolic end products. This causes the physical, chemical, and sensible properties of a food to change and the food is spoiled. 2. Intoxication 3. Plant Pathogens  –   causes disease and decreases in crop production 4. Animal Diseases  –   cause respiratory diseases in humans
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