AIT101 MICROBIOLOGY Lecture: Yeast Kamonchai Cha-aim, Ph.D. February 9th, 2015

Outline History of yeast Structure and life cycle of yeast Nature of yeast Applications of yeast in industries

Objectives To understand the nature, structures, and life cycles of yeast and mold. To explain the applications of yeast for the production of fermented products.

Figure 1. Classification of yeast and mold.

PART I: YEAST Saccharomyces cerevisiae

General Characteristics of Yeast Eukaryotic microorganism Unicellular or multicellular About 1,500 species Are all yeast useful? Cell size  3-6 μm or up to >40 μm Shape: oval, sphere, cylindrical, elongate form Sexual or asexual reproduction (budding  mitosis) Symmetric or asymmetric division Fermentation (not all yeast) Pathogens  causing infection in human

History of Yeast Egyptian (4000 B.C.) made bread and wine. However, nobody know what was the microbe play an important role for the biochemical process of fermentation…… ….Until 1857… Louis Pasteur discovered yeast

History of Yeast

Yeast has been used for proteins production since For example; Insulin, enzymes such as amylase, lipase, phosphatase In 1996, DNA sequencing of Saccharomyces cerevisiae was completed. 5,800 genes were identified Essential gene Nonessential gene

Figure 2. Homepage of SGD.

Structure and life cycle of Yeast Cell Structure Figure 3. Drawing diagram of yeast cell.

Structure and life cycle of Yeast Yeast Cell Wall Figure 4. Component of yeast cell wall. Periplasmic space

Structure and life cycle of Yeast Yeast Cell Wall Mannoprotein; Yeast wall mannoproteins are highly glycosylated polypeptides, often 50 to 95% carbohydrate by weight. Sugar can add 50,000 to 100,000 Da to the size of the mannoproteins.

Structure and life cycle of Yeast Yeast Cell Wall Glucan; The major component (about 85%) is a branched β-(1→3)-glucan of high molecular weight (about ) containing 3% of β-(1→6)-glucosidic interchain linkages. The minor component is a branched β-(1→6)- glucan.

Structure and life cycle of Yeast Yeast Cell Wall Glucan structure Figure 5. β-(1→3)-glucan linked β-(1→6)-glucosidic interchain glucan polymer

Structure and life cycle of Yeast Yeast Cell Wall Chitin; is a long-chain polymer of a N-acetyl glucosamine, a derivative of glucose. Figure 6. Units of N-acetylglucosamine; a polymer of chitin

Structure and life cycle of Yeast Yeast Cell Wall Membrane; selective permeable, protect cell, phospholipid bilayer and proteins

Structure and life cycle of Yeast Nucleus; The main function of the cell nucleus is to control gene expression and mediate the replication of DNA during the cell cycle.

Structure and life cycle of Yeast Nucleus; Yeast Chromosome

Structure and life cycle of Yeast Nucleus;  DAPI staining yeast nucleus (4',6-diamidino-2-phenylindole)  Hoechst33342 (Bisbenzimid)

Structure and life cycle of Yeast Vacuole; is essentially enclosed compartments which are filled with water containing inorganic and organic molecules including enzymes in solution.

Structure and life cycle of Yeast Vacuole; In general, the functions of the vacuole include: Isolating materials that might be harmful or a threat to the cell Containing waste products Containing water in plant cells Maintaining internal hydrostatic pressure within the cell Maintaining an acidic internal pH Containing small molecules Exporting unwanted substances from the cell

Structure and life cycle of Yeast Life cycle

Structure and life cycle of Yeast Budding Yeast Life cycle Two types of pheromone MAT a MAT α Receptor binding protein Shmoo structure Binding Yeast Cell

Structure and life cycle of Yeast Budding Yeast (G1 S G2 and M Phase)

Structure and life cycle of Yeast Nitrogen starvation in budding Yeast (Sporulation) Sporulation Medium: 10 g/l Potassium acetate 1 g/l Yeast extract 0.5 g/l Dextrose YPD Medium: 20 g/l Peptone 10 g/l Yeast extract 20 g/l Dextrose 1 µM

Structure and life cycle of Yeast Fission Yeast Life cycle

Structure and life cycle of Yeast Fission Yeast Life cycle Figure 7. A generation time of S. pombe between 2 and 4 hours

Nature of Yeast and Mold Where is yeast found in nature? On the skins of fruits and berries ( such as grapes, apples, or peaches) In exudates from plants (such as plant saps or cacti) Some yeasts are found in association with soil and insects.

Nature of Yeast and Mold Yeast and Temperature Cool temperature (below 15 o C) Stress Condition  Dormancy cells Warm temperature (15 – 30 o C) Optimal temperature for rapid growth yeast (25-35 o C) High temperature (40 o C) Stress Condition  Arrest growth

Application of Yeast Bioethanol Beer-wine industry Bread Source of protein/vitamin Make vaccine of Hepatitis B (recombinant DNA) Making Interferon  -glucan Mannoprotein: wine clarification

Applications of yeast and mold in industries Yeast Saccharomyces cerevisiae S. carlbergensis Kluyveromyces marxianus Saccharomycopsis fibuligera How to utilize them? Alcoholic beverage by sugar fermentation Baking bread Nutritional supplements Yeast extract Enzymes production

Applications of yeast and mold in industries Alcoholic beverage by sugar fermentation Figure 11. Scheme of glucose metabolic pathway to produce ethanol

Applications of yeast and mold in industries Baking bread Anaerobic respiration in yeast: Glucose Pyruvate Ethanol + CO 2

ALKOSEL® R397 ALKOSEL® R397 is a specific inactivated whole cell yeast (Saccharomyces cerevisiae) product containing the essential trace element selenium in its natural food form, L(+) selenomethionine. It is produced by growing yeast in the presence of measured amounts of selenium. This specific yeast strain absorbs selenium and biochemically transforms it into the highly bioavailable L(+) selenomethionine and other seleno-proteins. Selenomethionine is naturally found in edible plant protein but only at very low concentration. It is the most suitable form of selenium for animal nutrition.

Applications of yeast and mold in industries

Nutritional supplements Yeast Dietary Supplement

Applications of yeast and mold in industries Yeast extract

Applications of yeast and mold in industries Saccharomycopsis fibuligera Mycelial mat hyphaStarch degradation (showed clear zone)