Difference Between Fermentation and Glycolysis

Key Difference – Fermentation vs Glycolysis

Both fermentation and glycolysis are processes of converting complex molecules such as sugars and carbohydrates into simple forms. Fermentation uses yeast or bacteria in the process of conversion whereas glycolysis does not. This is the key difference between fermentation and glycolysis, and further differences will be discussed in this article.

What is Fermentation?

Fermentation is a metabolic process that converts sugar (primarily glucose, fructose, and sucrose) to acids, gases or alcohol. It basically occurs in yeast, bacteria and oxygen-starved muscle cells in order to ferment lactic acid. Krebs cycle and electron transport system do not occur in fermentation. However, the sole energy extraction pathway is glycolysis plus one or two extra reactions. It is basically the Regeneration of NAD+ from the NADH produced during glycolysis.

Types of Fermentation

Lactic acid fermentation and Alcohol fermentation are prominent types of fermentation.

Lactic Acid Fermentation

Lactic acid fermentation is also a similar processes where sugar is converted to energy. It is more often used in food preservation.

C6H12O6 (glucose) → 2 CH3CHOHCOOH (lactic acid)

Lactic acid fermentation happens in the presence of bacteria such as Lactobacillus acidophilus and fungi. NADH transfers its electron directly to pyruvate in lactic acid fermentation. Lactic acid fermentation can be seen  in yoghurt production and inside the muscle cells.

Alcohol Fermentation

It is a process in which the sugars – glucose, fructose and sucrose in food are converted to energy. Bread, some tea (Kimbucha) and beverages (alcoholic – beer wine, whisky, vodka, and rum) are produced using alcoholic fermentation.

C6H12O6 (glucose) → 2 C2H5OH (ethanol) + 2 CO2 (carbon dioxide)

Yeast and certain bacteria can perform ethanol fermentation. In ethanol fermentation, NADH donates its electrons to a derivative of a pyruvate, producing ethanol as an end product.

Uses of Fermentation

Beer, Wine, Yoghurt, Cheese, Sauerkraut, Kimchi and Pepperoni are some examples of products produced by fermentation. Fermentation is also used in the sewage treatment, industrial alcohol production, and in the production of hydrogen gas.

Benefits of Fermentation

Bacteria produced during fermentation (probiotics) may be beneficial to the digestive system. In addition, preserving foods by fermentation can increase their nutritional value since fermentation increase the vitamin level.

Difference Between Fermentation and Glycolysis

Ethanol Fermentation

What is Glycolysis?

Glycolysis is defined as an enzymatic breakdown of carbohydrates (as glucose) by way of phosphate derivatives with the production of pyruvic or lactic acid and energy stored in high-energy phosphate bonds of ATP.

It is also known as “sweet splitting process.” It is a metabolic pathway that occurs in the cytosol of cells in living organisms. This can either function in the presence or absence of oxygen. Therefore, it can be divided as aerobic and anaerobic glycolysis.  Aerobic glycolysis yields more ATP than anaerobic process. With the presence of oxygen, it produces pyruvate and 2ATP molecules are produced as the net energy form.

Anaerobic glycolysis is the only effective means of energy production during short, intense exercise providing energy for a period of 10 seconds to 12 minutes.

The overall reaction can be expressed as follows.

Glucose + 2 NAD+ + 2 Pi + 2 ADP → 2 pyruvate + 2 NADH + 2 ATP + 2 H+ + 2 H2O + heat

Pyruvate is oxidized to acetyl-CoA and CO2 by the pyruvate dehydrogenase complex (PDC). It’s located in mitochondria of eukaryotic and cytosol of prokaryotes.

The glycolysis occurs, with variation, nearly in all organisms, both aerobic and anaerobic.

Key Difference - Fermentation vs Glycolysis

The metabolic pathway of glycolysis converts glucose to pyruvate by via a series of intermediate metabolites.

What is the difference between Fermentation and Glycolysis?

Definition of Fermentation and Glycolysis:

Fermentation: Fermentation is a metabolic process that converts sugar into acids, gases or alcohol.

Glycolysis: Glycolysis is an enzymatic breakdown of carbohydrates.

Characteristics of Fermentation and Glycolysis:

Oxygen Usage:

Fermentation: Fermentation does not use oxygen.

Glycolysis: Glycolysis uses oxygen.


Fermentation: Fermentation is considered as anaerobic.

Glycolysis: Glycolysis can be anaerobic or aerobic.

ATP Yield:

Fermentation:  Zero energy is gained during fermentation.

Glycolysis:  2 ATP molecules are produced.


Fermentation: Fermentation has 2 basic phases: lactic acid fermentation and ethanol fermentation.

Glycolysis: Glycolysis is classified into Aerobic and anaerobic glycolysis

Microorganism’s Involvement:

Fermentation: Bacteria and yeast are involved in fermentation.

Glycolysis: Bacteria and yeast are involved in Glycolysis.

Production of Ethanol or Lactic acid

Fermentation: Fermentation produces ethanol or lactic acid.

Glycolysis: Glycolysis does not produce ethanol or lactic acid.

Use of Pyruvic Acid

Fermentation: Fermentation starts with the use of Pyruvic acid.

Glycolysis: Glycolysis produces Pyruvic acid.

Fate of Pyruvic Acid

Fermentation: Pyruvic acid is converted into waste product

Glycolysis: Glycolysis produces Pyruvic acid to use to generate energy. Ex- aerobic respiration.

Image Courtesy:

“Ethanol fermentation” By Davidcarmack – Own work (CC BY-SA 3.0) via Commons Wikimedia

“Glycolysis metabolic pathway 3 annotated” By Thomas Shafee – Own work (CC BY 4.0) via Commons Wikimedia