1. Unit 2: Bacterial Metabolism and Fermentation

2. Fermentation and Pasteurization
Pasteur showed that microbes are responsible for fermentation
Fermentation is the conversion of sugar to alcohol or acid
Fermentation is used to make cheese, yogurt, beer and wine
Microbial growth is also responsible for spoilage of food
Bacteria that use alcohol and produce acetic acid spoil wine by turning it to vinegar (acetic acid) and bacteria that utilize lactose to produce lactic acid transform milk into yogurt

3. Fermentation and Pasteurization
Pasteur demonstrated that these spoilage bacteria could be killed by heat that was not hot enough to evaporate the alcohol in wine
Pasteurization is the application of a high heat for a short time
Figure 1.4

4. A Nutritional Classification of Organisms
Other energy sources include electricity, nuclear or thermal.
Figure 5.28

5. A Nutritional Classification of Organisms
Figure 5.28

6. A Nutritional Classification of Organisms
Figure 5.28

7. Metabolic Diversity among Organisms
Nutritional Type
Energy Source
Carbon Source
Example
Photoautotroph
Light
CO2
Oxygenic: Cyanobacteria plants
Anoxygenic: Green, purple bacteria
Photoheterotroph
Organic compounds
Green, purple nonsulfur bacteria
Chemoautotroph
Chemical
Iron-oxidizing bacteria
Chemoheterotroph
Fermentative bacteria
Animals, protozoa, fungi, bacteria.

8. Carbohydrate Catabolism
The breakdown of carbohydrates to release energy
Glycolysis
Krebs cycle
Electron transport chain

9. A Summary of Respiration
Aerobic respiration: The final electron acceptor in the electron transport chain is molecular oxygen (O2).
Anaerobic respiration: The final electron acceptor in the electron transport chain is not O2 (rather an inorgainc molecules containing sulfate, nitrate, nitrite, carbonate, etc..).
Yields less energy than aerobic respiration because only part of the Krebs cycles operates under anaerobic conditions.

10. Glycolysis
The oxidation of glucose to pyruvic acid produces ATP and NADH

11. Preparatory Stage of Glycolysis
2 ATP are invested
Glucose is split to form 2 glucose-3 -phosphate
Figure 5.12, steps 1–5

12. Cellular Respiration
Oxidation of molecules liberates electrons for an electron transport chain
ATP is generated by oxidative phosphorylation

13. Energy-Generating Stage of Glycolysis
2 glucose-3-phosphate oxidized to 2 pyruvic acid
4 ATP produced
2 NADH produced
Figure 5.12, steps 6–10

15. Overall Result of Glycolysis
Glucose + 2 ATP + 2 ADP + 2 PO4– + 2 NAD+  2 pyruvic acid + 4 ATP + 2 NADH + 2H+

17. Intermediate Step
Pyruvic acid (from glycolysis) is oxidized and decarboyxlated
Figure 5.13

18. Acetyl CoA

19. The Krebs Cycle

20. Carbohydrate Catabolism
Pathway
Eukaryote
Prokaryote
Glycolysis
Cytoplasm
Intermediate step
Krebs cycle
Mitochondrial matrix
ETC
Mitochondrial inner membrane
Plasma membrane

21. The Electron Transport Chain
A series of carrier molecules that are, in turn, oxidized and reduced as electrons are passed down the chain
Energy released can be used to produce ATP by chemiosmosis

22. Chemiosmotic Generation of ATP
Figure 5.16

23. An Overview of Chemiosmosis
Figure 5.15

24. Fermentation Any spoilage of food by microorganisms (general use)
Any process that produces alcoholic beverages or acidic dairy products (general use)
Any large-scale microbial process occurring with or without air (common definition used in industry)

25. Fermentation Scientific definition:
Releases energy from oxidation of organic molecules
Does not require oxygen
Does not use the Krebs cycle or ETC
Uses an organic molecule as the final electron acceptor

26. Figure 5.11

27. An Overview of Fermentation
Figure 5.18a

28. Fermentation Alcohol fermentation: Produces ethanol + CO2
Lactic acid fermentation: Produces lactic acid
Homolactic fermentation: Produces lactic acid only
Heterolactic fermentation: Produces lactic acid and other compounds

29. Types of Fermentation
Figure 5.19

31. End-Products of Fermentation
Figure 5.18b

32. A Fermentation Test
Figure 5.23

33. Types of Fermentation
Table 5.4

34. Types of Fermentation
Table 5.4

35. Requirements of ATP Production
Figure 5.27