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Homolactic Fermentation vs. Heterolactic Fermentation: What's the Difference?

Edited by Janet White || By Harlon Moss || Published on February 6, 2024
Homolactic fermentation produces only lactic acid from sugars, while heterolactic fermentation produces lactic acid, ethanol, and CO2 from sugars.

Key Differences

Homolactic fermentation involves the conversion of glucose or other sugars primarily into lactic acid. It is a simpler process where one molecule of glucose is converted into two molecules of lactic acid. This is typical in many bacteria and some muscle cells. Heterolactic fermentation, however, is more complex and involves the production of not just lactic acid, but also ethanol and carbon dioxide. It occurs in certain bacteria like those used in the production of yogurt and kefir.
The process of homolactic fermentation does not require oxygen (anaerobic process) and is an efficient way to produce energy quickly, as in muscle cells during intense exercise. This type of fermentation is characterized by the end product being solely lactic acid. In contrast, heterolactic fermentation can produce a mixture of products: lactic acid, ethanol, and CO2. This variability makes heterolactic fermentation important in food industry for flavor and texture development in fermented foods.
Homolactic fermentation is a straightforward fermentation pathway where pyruvate is directly reduced to lactic acid using NADH as a reducing agent. This process is common in certain bacteria, like Lactobacillus, and in animal cells. On the other hand, heterolactic fermentation involves a more complex pathway, typically the phosphoketolase pathway, leading to the simultaneous production of lactic acid, ethanol, and CO2, as seen in some species of Lactobacillus and Leuconostoc.
In homolactic fermentation, the primary purpose is rapid ATP production, especially in muscle cells under anaerobic conditions, and in certain microorganisms. This process is crucial in dairy fermentation, where it contributes to the sour taste of fermented milk products. Heterolactic fermentation is notable for its role in food fermentation, where the variety of end products contributes to the complexity of flavors and textures in fermented foods like sourdough bread and certain dairy products.
The efficiency of homolactic fermentation lies in its simplicity and quick energy production, making it vital in certain physiological and industrial processes. The end product, lactic acid, has various applications, including food preservation and flavoring. Heterolactic fermentation, with its production of multiple end products, is key in food processing, where it enhances flavor, texture, and shelf life of various fermented products.

Comparison Chart

End Products

Lactic Acid
Lactic Acid, Ethanol, CO2


Direct reduction of pyruvate to lactic acid
Phosphoketolase pathway producing multiple products

Oxygen Requirement


Typical Organisms

Lactobacillus, muscle cells
Lactobacillus, Leuconostoc


Energy production in muscles, dairy fermentation
Diverse food fermentation (yogurt, sourdough)

Homolactic Fermentation and Heterolactic Fermentation Definitions

Homolactic Fermentation

Simple fermentation pathway used by certain bacteria.
Lactobacillus species utilize homolactic fermentation in dairy processing.

Heterolactic Fermentation

Complex fermentation involving the phosphoketolase pathway.
Certain Lactobacillus strains perform heterolactic fermentation in sourdough.

Homolactic Fermentation

Direct reduction of pyruvate to lactic acid.
Cheese making employs homolactic fermentation for acid production.

Heterolactic Fermentation

Fermentation resulting in a mix of metabolic products.
Heterolactic fermentation contributes to the unique flavor of some yogurts.

Homolactic Fermentation

Anaerobic process producing lactic acid from pyruvate.
Muscle cells perform homolactic fermentation during intense exercise.

Heterolactic Fermentation

Used in food processing for flavor and texture development.
Heterolactic fermentation is key in creating certain artisanal cheeses.

Homolactic Fermentation

Fermentation process resulting in rapid ATP production.
Homolactic fermentation provides quick energy in anaerobic conditions.

Heterolactic Fermentation

Produces lactic acid, ethanol, and CO2 from sugars.
Kefir is made using heterolactic fermentation.

Homolactic Fermentation

Conversion of sugars into lactic acid.
Yogurt production often involves homolactic fermentation.

Heterolactic Fermentation

Anaerobic fermentation creating multiple end products.
Fermented vegetables often undergo heterolactic fermentation.


What are typical uses of homolactic fermentation?

Used in dairy fermentation and in muscles during anaerobic exercise.

Where is heterolactic fermentation commonly found?

In food fermentation processes like in yogurt and sourdough bread.

How does heterolactic fermentation differ from homolactic?

Heterolactic produces not only lactic acid but also ethanol and CO2.

What is homolactic fermentation?

It's the process of converting glucose into lactic acid.

Is homolactic fermentation anaerobic?

Yes, it occurs in the absence of oxygen.

Can homolactic fermentation occur in human cells?

Yes, particularly in muscle cells under strenuous exercise.

What flavors does heterolactic fermentation add to food?

It contributes complex flavors and textures to fermented foods.

What role does CO2 play in heterolactic fermentation?

CO2 contributes to the texture and leavening in fermented foods.

How does heterolactic fermentation enhance food taste?

It adds complexity and depth to the flavors of fermented foods.

What is the main product of homolactic fermentation?

Lactic acid is the primary product.

Does heterolactic fermentation produce alcohol?

Yes, it produces ethanol as one of the byproducts.

Is oxygen needed for heterolactic fermentation?

No, it's also an anaerobic process.

What organisms typically perform heterolactic fermentation?

Certain bacteria like Lactobacillus and Leuconostoc.

How is homolactic fermentation beneficial in food preservation?

Lactic acid produced helps in preserving and flavoring food.

How is ATP related to homolactic fermentation?

Homolactic fermentation provides rapid ATP production in cells.

Does heterolactic fermentation require specific temperatures?

Yes, it usually requires controlled temperatures for optimal results.

What is a common example of homolactic fermentation in dairy?

Yogurt production is a typical example.

Can heterolactic fermentation be used in beverage production?

Yes, especially in some traditional fermented beverages.

Are there health benefits to homolactic fermentation?

It can promote gut health and aid in food preservation.

What happens to glucose in homolactic fermentation?

It is directly converted into lactic acid.
About Author
Written by
Harlon Moss
Harlon is a seasoned quality moderator and accomplished content writer for Difference Wiki. An alumnus of the prestigious University of California, he earned his degree in Computer Science. Leveraging his academic background, Harlon brings a meticulous and informed perspective to his work, ensuring content accuracy and excellence.
Edited by
Janet White
Janet White has been an esteemed writer and blogger for Difference Wiki. Holding a Master's degree in Science and Medical Journalism from the prestigious Boston University, she has consistently demonstrated her expertise and passion for her field. When she's not immersed in her work, Janet relishes her time exercising, delving into a good book, and cherishing moments with friends and family.

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