Yeasts and their uses

a small presentation about yeasts and their uses

1. Yeast Saccharomyces cerevisiae

2. Introduction In 1680, Dutch naturalist Anton van Leeuwenhoek first microscopically observed yeast. In 1857, French microbiologist Louis Pasteur proved in the paper " Mémoire sur la fermentation alcoolique , " that alcoholic fermentation was conducted by living yeasts and not by a chemical catalyst. 2

3. What are Yeasts Yeasts are eukaryotic , single-celled microorganisms classified as members of the fungus kingdom. 1,500 species are currently identified( 1% of all fungal species). Yeast sizes vary greatly typically measuring 3–4 µm in diameter The most common mode of vegetative growth in yeast is asexual reproducing by budding. 3

4. Yeasts do anaerobic (in absence of oxygen) cell respiration (fermentation) to produce ethanol and carbon dioxide from sugar (glucose). C 6 H 12 O 6 → 2 C 2 H 5 OH + 2 CO 2 Fermetation process 4

5. Importance & Uses of yeast 5 Yeasts have a lot of economic value to mankind for example : Bread making (Baking) Alcoholic beverages Nutrition and Probiotics Industrial ethanol production Scientific research

6. Records of using yeast date back to the ancient Egyptians, being used in baking as a leavening agent, where it converts the fermentable sugars present in dough into the gas carbon dioxide. Yeast not only helps bread dough rise, but it also aids in developing and strengthening proteins in the dough and adds to its flavor . Yeast may be best known as the agent in bread that makes it rise. When you add yeast to your flour and water mixture, it breaks down the large starch molecules into simple sugars. During this process, the yeast creates carbon dioxide and ethyl alcohol, which make the air bubbles that causes the bread dough to grow. Bread Making 6

7. Beer & Wine making production of beer is by steeping a starch source in water and fermenting the resulting sweet liquid with yeast. The type of yeast used will affect the type and flavor of beer produced. Commonly used Yeast is S. Cerevisiae . In Wine making fermentation can be from naturally occurring yeasts on the skin of the grape or using a starter culture of Saccharomyces cerevisiae ‘in which case the juice is inoculated with populations of yeast’’. Brewing 7

8. 8 Nutrition & Probiotics Yeast is used in nutritional supplements, especially those marketed to vegans. It is often referred to as "nutritional yeast" when sold as a dietary supplement yaest is usually S.cerevisiae . It is an excellent source of protein and vitamins, especially the B- complex vitamins Probiotics Some probiotic supplements use the yeast S. boulardii to maintain and restore the natural flora in the gastrointestinal tract. Nutrition

9. 9 Industrial ethanol production In the industry of fermentation , yeast is used not only in food industries to make bread, wine and beer, but also in non-food industries, such as the Biofuel industry, to produce ethanol. Bioethanol is the principle fuel used as a petrol substitute for road transport vehicles which is a clear colourless liquid, biodegradable, low in toxicity and causes little environmental pollution .

10. 10 Scientific research Yeast are Model organisms in genetics as it is one of the simplest eukaryotic Studying the biology of yeasts has enabled scientists to work out the connections between genes and proteins, and the functions they carry out in our cells by studying their homologues in the yeast also the study of fundamental cellular processes such as the cell cycle, DNA replication,Recombination,cell division and metabolism. Genetic manipulation in yeast is easy and cheap compared to similar experiments in more complex animals Various yeast species have been genetically engineered to efficiently produce various drugs, About 20% of biopharmaceuticals are produced in S.  cerevisiae , including insulin, vaccines for hepatitis, and human serum albumin

11. Thank you