PASTEUR EFFECT.pptx

PG AND RESEARCH DEPARTMENT OF MICROBIOLOGY,SRI PARAMAKALYANI COLLEGE,ALWARKURICHI.

1. SRI PARAMAKALYANI COLLEGE REACCREDITED WITH B GRADE WITH A CGPA OF 2.71 IN THE SECOND CYCLE OF NAAC AFFILIATED TO MANOMANIUM SUNDARANAR UNIVERSITY, TIRUNELVELI. ALWARKURICHI 627 412, TAMIL NADU, INDIA POST GRADUATE & RESEARCH CENTRE DEPARTMENT OF MICROBIOLOGY (Government Aided) ACADEMIC YEAR 2021-2022 I sem core: Microbial PHYSIOLOGY AND METABOLISM - (zmbm13) UnIT - 3 Pasteur’s effect a.muthukumar Reg no:20211232516116 I M.Sc microbiology Spkc-alwarkurichi Assigned on : 05/12/2021 Taken on:12/01/2022 Submitted to Guide: Dr.s.viswanathan Assistant professor & head Department microbiology Spkc-alwarkurichi

2. PASTEUR’S EFFECT synopsis Introduction Discovery Fermentation Respiration Main Difference Between Fermentation & Respiration Pasteur Effect Explanations

3. INDTRODUCTION The Pasteur effect is  an inhibiting effect of oxygen on the fermentation process . It is a sudden change from anaerobic to aerobic process.

4. The effect was discovered in 1857 by  Louis Pasteur , who showed that aerating yeasted broth causes  yeast  cell growth to increase, while conversely,  fermentation  rate decreases. The realization that specific organisms were involved in fermentation was further supported by Pasteur’s studies of butyric acid fermentation. These studies led Pasteur to the unexpected discovery that the fermentation process could be arrested by passing air (that is,  oxygen ) through the fermenting fluid, a process known today as the Pasteur effect. He concluded that this was due to the presence of a life-form that could function only in the absence of oxygen. This led to his introduction of the terms  aerobic  and  anaerobic  to designate organisms that live in the presence or absence of oxygen, respectively. DISCOVERY PASTEUR EFFECT

5. Fermentation is the chemical breakdown of organic substrates like glucose by microorganisms like bacteria and yeast. The net yield of fermentation is only 2 ATPs. The process of fermentation occurs in two steps: glycolysis and partial oxidization of pyruvate. There are two types of fermentation known as ethanol fermentation and lactic acid fermentation. Ethanol fermentation occurs in yeast in the absence of oxygen. Hence, they are called facultative anaerobes. Lactic acid fermentation occurs in bacteria In the absence of oxygen. FERMENTATION

6. During glycolysis, glucose is broken down into two pyruvate molecules, generating 2 ATPs as the net gain. Other than that, two molecules of NADH are formed by obtaining electrons from glyceraldehyde­3­phosphate. During ethanol fermentation, pyruvate is decarboxylated into acetaldehyde by removing carbon dioxide. Acetaldehyde is converted into ethanol by using the hydrogen atoms of the NADH. During lactic acid fermentation, pyruvate is converted into lactic acid, which is then oxidized into lactate. The overall chemical reaction for ethanol fermentation and lactic acid fermentation are given below. Ethanol Fermentation: C6 H12 O6 → 2C2 H5 OH + 2CO2 + 2ATP Lactic Acid Fermentation: C6 H12 O6 → 2C3 H6 O3 + 2ATP

7. RESPIRATION Respiration is the set of chemical reactions involved in the production of energy by completely oxidizing food. It releases carbon dioxide and water as by­ products. Respiration is the most abundant and most efficient process among the processes of energy production. During respiration, 36 ATPs are produced. The whole process occurs in the cytoplasm and mitochondria. Respiration occurs through three steps: glycolysis, citric acid cycle and electron transport chain

8. Glycolysis occurs in the cytoplasm of the cell in the same way it occurs during fermentation. The two pyruvate molecules produced in the glycolysis is transferred into the mitochondrial matrix. They release two carbon dioxide molecules, one from each and become acetyl­CoA during oxidative decarboxylation.

9. This acetyl­CoA enters into the citric acid cycle , which is also known as Krebs cycle . During the citric acid cycle, a single glucose molecule is completely oxidized into six carbon dioxide molecules, generating 2 GTPs, 6 NADH and 2 FADH .

10. These NADH and FADH are combined with oxygen, generating ATP during oxidative phosphorylation, which occurs in the inner mitochondrial membrane. During the oxidative phosphorylation, electrons in NADH and FADH are transferred through a series of electron carriers called electron transport chain . The net yield of ATPs is thirty six in respiration.

11. Fermentation and respiration are two types of cellular processes, involved in the breaking down of glucose in the cell. Both fermentation and respiration are catabolic processes, generating energy in the form of ATP. The main difference between fermentation and respiration is that during fermentation, NADH is not used in the oxidative phosphorylation in order to generate ATP whereas, during respiration, NADH is used in the oxidative phosphorylation in order to generate three ATPs per NADH. MAIN DIFFERENCE – FERMENTATION VS RESPIRATION

12. PASTEUR EFFECT EXPLANATIONS The effect can be explained; as the yeast being  facultative anaerobes  can produce energy using two different metabolic pathways. While the oxygen concentration is low, the product of  glycolysis ,  pyruvate , is turned into  ethanol  and  carbon dioxide , and the energy production efficiency is low (2  moles  of  ATP  per mole of  glucose ). If the oxygen concentration grows, pyruvate is converted to  acetyl CoA  that can be used in the  citric acid cycle , which increases the efficiency to 31 moles of ATP per mole of glucose (it depends on which shuttle is used for reducing the reducing equivalent, NADH, that is formed in the cytosol). Therefore, about 15 times as much glucose must be consumed anaerobically as aerobically to yield the same amount of ATP.

13. Under anaerobic conditions, the rate of glucose metabolism is faster, but the amount of ATP produced (as already mentioned) is smaller. When exposed to aerobic conditions, the ATP and Citrate production increases and the rate of  glycolysis  slows, because the ATP and citrate produced act as  allosteric inhibitors  for  phosphofructokinase 1 , the third enzyme in the glycolysis pathway. The Pasteur effect will only occur if glucose concentrations are low (<2 g/L) and if other nutrients, mostly nitrogen, are limited.

14. Fig: Yeasts can survive in the presence and absence of oxygen. In the presence of oxygen, yeast undergo aerobic respiration and convert carbohydrates (sugar source) into carbon dioxide and water.  In the absence of oxygen, yeasts undergo fermentation and convert carbohydrates into carbon dioxide and alcohol.

15. REFERENCES   Lehninger , Albert (2008).  Principles of Biochemistry . New York, NY: W.H. Freeman and Company. pp.  539 .  ISBN   978-0-7167-7108-1 . https://en.wikipedia.org/wiki/Pasteur_effect Krebs, Hans  (1972). "The Pasteur effect and the relations between respiration and fermentation". Essays in Biochemistry (8): 1–34. Pasteur Effect - an overview | ScienceDirect Topics https://www.sciencedirect.com  › ... 5 . Difference Between Fermentation and ... - ResearchGate https://www.researchgate.net  6. https://www.britannica.com/science/Pasteur-effec t

16. SKILLS ACHIEVED FROM SEMINAR Comunication skills Confidence Gained subject knowledge better Presentation skills Motivations

17. THANK YOU The Chairman. The Secretary. Management Committee. The Principle,Sri Paramakalyani College. The Head - Department Of Microbiology. The staff Members - Department Of Microbiology.