Fermentation and Glycolysis Overview

Fermentation Overview

• Fermentation is a process of energy extraction from nutrients in the absence of oxygen.
• Alcoholic and lactic acid fermentation are two common types.
• Fermentation is less efficient than aerobic respiration, producing fewer ATP molecules.

Glycolysis

• Glycolysis is the first stage of glucose metabolism.
• This process is activated when energy is needed.
• One glucose molecule converts to two pyruvate molecules.
• It's crucial for organisms to extract energy from nutrients.
• The production of 2 ATP and 2 NADH for each glucose molecule.
• Pyruvate has several possible fates.

Fates of Pyruvate

• Aerobic Conditions (Oxygen present): Pyruvate is converted to acetyl-CoA, entering aerobic metabolism.
• Anaerobic Conditions (No Oxygen): Pyruvate is converted to lactate or alcohol, entering anaerobic metabolism.

Lactic Acid Fermentation

• Occurs when oxygen is unavailable, often during strenuous exercise.
• Depletes oxygen in muscle tissues, leading to a switch from respiration to fermentation.
• Pyruvic acid gains a hydrogen from NADH, converting it to lactic acid and releasing energy used to create ATP.
• The process temporarily replaces aerobic respiration for ongoing energy production.
• Cells use excess oxygen to replenish oxygen supply in muscle cells.
• This process leads to muscle fatigue, burning, and pain.

Alcoholic Fermentation

• Occurs in yeasts and some bacteria (e.g., Saccharomyces cerevisiae).
• Pyruvic acid is broken down, producing alcohol and carbon dioxide (CO2).
• CO2 and ethanol are released and used to form ATP.
• Yeasts contain zymase enzymes. These metabolize carbohydrates without oxygen.
• Ethanol and CO2 are produced during this process.
• This process is used in wine and beer production.

Yeast Growth Phases

• Lag phase: Microbes grow and adapt to the new environment.
• Exponential (log) phase: Maximum biomass production as cells are the most active and consume significant amounts of nutrients.
• Stationary phase: Nutrient depletion halts growth and biomass remains constant.
• Death phase: Dying cells exceed the newly generated cells, and biomass decreases.

Fermentation Products and Applications

• Fermentation is widely used in food production (e.g., yogurt, cheese, bread, beer, wine, olives, vinegar, soy sauce, sauerkraut.)
• Certain organisms like propionibacterium can produce propionic acid, crucial in Swiss cheese.
• Lactic acid bacteria produces lactic acid, involved in various food products (e.g., cheese, yogurt).
• Saccharomyces cerevisiae produces CO2 and ethanol in beer and wine production.

Types of Commercially Important Fermentation

• Microbes (Biomass/enzymes/metabolites) are generated during fermentation.
• Some produce microbial enzymes.
• Some produce microbial metabolites.
• Others generate recombinant products.
• Some modify added compounds during the process.

Bioreactor Components

• Agitator/Agitation system: Uniform mixing of nutrients, microorganisms, and gases.
• Sparger (Air): Introduces gases (mostly oxygen) to maintain respiration in microbes.
• Sensor probes: Monitors temperature, pH, dissolved oxygen, and agitation speed.
• Sterile Inlet: Introduces nutrients and inoculums for sterilization.
• Product Outlet/Effluent: Harvests fermented products after fermentation is complete.

Fermentation Process Flow

• Media formulation: Growth media components.
• Sterilization: Sterilizing all fermentation equipment and media.
• Pure culture production: Obtaining a sufficient quantity of pure organisms.
• Growth conditions: Optimizing culture growing conditions in fermenter.
• Product extraction and purification.
• Effluents disposal.

Transition from Shake Flask to Bioreactor

• The process starts with screening and optimizing growth medium in a shake flask.
• Then, the process scales up and production occurs in a bioreactor.

This quiz explores the concepts of fermentation, glycolysis, and the different fates of pyruvate. Learn about the processes of energy extraction in anaerobic conditions and the role of glycolysis in glucose metabolism. Understand the significance of lactic acid fermentation in muscle activity during exercise.