Lecture Notes: Bacterial Fermentation

Overview

• Focus on two main types of fermentation: Lactic Acid Fermentation and Alcoholic Fermentation.
• Important for regenerating NAD+ which is essential for glycolysis.
• Fermentation allows ATP production in the absence of oxygen.

Glycolysis and Fermentation

• Glycolysis:
  • Converts glucose to pyruvate/pyruvic acid.
  • Produces ATP and NADH.
  • Without oxygen, NADH cannot be used in the electron transport chain, needs to be converted back to NAD+.

Lactic Acid Fermentation

• Process:
  • Pyruvate is reduced to lactate, converting NADH back to NAD+.
  • Allows continued ATP production through glycolysis.
  • Relevant in muscles during oxygen deficit; lactate is returned to the liver, converted back to pyruvate for cellular respiration.
• Examples:
  • Used by bacteria like Streptococcus, Lactobacillus, Bacillus.
  • Common in fermented foods: yogurt, sauerkraut, pickles, chocolate.
  • Preserves food by acid production; used historically for food preservation.

Alcoholic Fermentation

• Process:
  • Pyruvate is decarboxylated to acetaldehyde, then reduced to ethanol.
  • Converts NADH back to NAD+, enabling further glycolysis and ATP production.
• Important for industries like brewing and winemaking.

Historical and Practical Context

• Fermentation as a food preservation method predates refrigeration.
• Pasteurization (Louis Pasteur):
  • Prevents spoilage of wine by killing vinegar-producing bacteria through heat.
  • Integral to preserving quality in wine and dairy industries.

Summary

• Fermentation provides an anaerobic pathway for ATP production by regenerating NAD+ from NADH.
• Lactic acid and alcoholic fermentation serve different roles in biology and industry.
• Preservation through fermentation has historical importance and continues to be relevant today.