Fermentation normally occurs in an anaerobic environment. In the presence of O2, NADH and pyruvate are used to generate ATP in respiration. Some fermentation processes involve obligate anaerobes, which cannot tolerate oxygen.

Fermentation is a metabolic process that occurs in the absence of oxygen, also known as anaerobic respiration. During fermentation, organic compounds such as glucose are broken down into simpler compounds such as alcohol and lactic acid, releasing energy in the process. This process is used by cells when oxygen is not available for aerobic respiration, such as during intense exercise.

Types of Fermentation:

There are two main types of fermentation:

1. Alcoholic fermentation: In this type of fermentation, glucose is broken down into ethanol and carbon dioxide. This process occurs in yeast cells and is used in the production of alcoholic beverages such as beer and wine.

2. Lactic acid fermentation: This type of fermentation occurs in muscle cells when oxygen is not available for aerobic respiration. Glucose is broken down into lactic acid, which can cause muscle fatigue and soreness.

Benefits of Fermentation:

Fermentation has several benefits, including:

1. Preservation of food: Fermentation is used to preserve food by creating an acidic environment that inhibits the growth of harmful bacteria.

2. Production of food and beverages: Fermentation is used to produce a variety of food and beverages, including bread, cheese, yogurt, beer, and wine.

3. Production of biofuels: Fermentation is used to produce biofuels such as ethanol, which can be used as a renewable energy source.

In conclusion, fermentation is an important metabolic process that occurs in the absence of oxygen and is used by cells to release energy when oxygen is not available. It has several benefits, including the preservation of food, production of food and beverages, and production of biofuels.

Fermentation occurs the absence of O2... so it is an Anaerobic respiration.