Oenococcus oeni characteristics, morphology, applications

Sherman Hoover

The Oenococcus oeni it is a gram positive bacterium that is highly resistant to extreme conditions such as high concentrations of alcohol and acidic pH. It is a bacterium whose habitat is linked to the wine industry. Taking this into account, for some time it has been one of the most used bacteria in the wine-making process..

Oenococcus oeni has a relatively new name, since until 1995 it was known as Leuconostoc oeni. From a series of studies and experimental investigations it was determined that it had certain differences with the bacteria of the genus Leuconostoc.

Oenococcus oeni. Source: Wikipedia

Due to this, it became part of the genus Oenococcus, of which it was the only known species until 2006, the year in which a new species was discovered: Oenococcus kitaharae.

The bacteria Oenococcus oeni It is one of the most representative examples of the use that can be given to non-pathogenic microorganisms for the benefit and benefit of man..

Article index

  • 1 Taxonomy
  • 2 Morphology
  • 3 Features
    • 3.1 It is catalase negative
  • 4 Applications
    • 4.1 Malolactic fermentation
  • 5 References


The taxonomic classification of this bacterium is as follows:

Domain: Bacterium

Edge: Firmicutes

Class: Bacilli

Order: Lactobacillales

Family: Leuconostocaceae

Gender: Oenococcus

Species: Oenococcus oeni.


The Oenococcus oeni It is a bacterium that has an ellipsoidal shape, it has an average size of 0.5-0.7 microns in diameter. When observed under the microscope, it can be noticed that they are grouped into chains or pairs..

Like all gram positive bacteria, it has a thick cell wall that is made up of peptidoglycan. They do not have any type of teichoic acid.

Likewise, no type of extensions such as cilia or flagella emerge from the cell surface..

From the genetic point of view, the genome of the bacterium is contained in a single circular chromosome in which there are 1691 genes that code for the expression of proteins.


It is gram positive

Thanks to the thick peptidoglycan cell wall that cells of Oenococcus oeni, when subjected to the Gram staining process, they retain particles of the dye. Due to this, they adopt the characteristic violet coloration typical of gram positive bacteria..

It is catalase negative

This bacterium is not capable of synthesizing the enzyme catalase. Therefore, it cannot unfold the hydrogen peroxide molecule (HtwoORtwo) in water and oxygen.

It is facultative anaerobic

The Oenococcus oeni it can survive both in environments with oxygen availability, and in its absence. This is because their metabolic processes are able to adapt to obtain energy, either from oxygen or from fermentation..

It is heterofermentative

This bacterium can carry out the fermentation process taking certain sugars as a starting point. This implies that the bacterial cell is capable of producing lactic acid, acetic acid, carbon dioxide, ethanol and diacetyl, among others. Mainly from glucose.

They reproduce by bipartition

The Oenococcus oeni reproduces through asexual reproduction process known as bipartition.

In this process, a duplication of the genetic material of the cell occurs first, followed by a division of the cell cytoplasm, resulting in two cells exactly the same as the progenitor cell..

Not mobile

This bacterium is not able to move freely, since it does not have cilia or flagella, which are the organs designed in bacteria for this purpose..

It is resistant to harsh conditions

Studies have determined that this bacterium is capable of resisting pH levels of up to 3 and ethanol concentrations greater than 10%..

It is not sporulated

This bacterium does not produce spores of any kind during its life cycle..


The bacterium is closely linked to the production of wine, so its habitat is must and wine.

Require a nutrient-rich growing medium

To be able to develop properly in a culture medium, it must necessarily contain vitamins, amino acids and ions such as Mg+two, Mn+two, Na+ and K+.

Carries out malolactic fermentation

The Oenococcus oeni plays an important role during the wine production process, as it undergoes malolactic fermentation.

It is a highly complex process by which, through the action of various enzymes, the malic acid that is present in the pulp of fruits (such as grapes) is transformed into lactic acid.

It is one of the favorite bacteria in winemaking

This is so for several reasons:

  • It does not cause degradation of compounds such as tartaric acid or ethanol, which are necessary to ensure the stability and quality of the wine.
  • They perform malolactic fermentation quickly, without generating unwanted intermediate products.
  • It has high resistance to extreme conditions such as a low pH, high levels of alcohol, among others.
Source: Pixabay


The Oenococcus oeni It is a non-pathogenic bacteria that is widely used in the winemaking process. It is the species of bacteria most used in malolactic fermentation.

Malolactic fermentation

The winemaking process involves two types of fermentation: alcoholic and malolactic. The first process is alcoholic fermentation, in which the sugars contained in the grapes are metabolized to obtain mainly ethyl alcohol. Later, another type of fermentation takes place, called malolactic fermentation..

This process aims to obtain lactic acid from glucose and malic acid. The latter is found in various concentrations in grape must. This is not beneficial for the wine because it gives it a harsh taste..

This is where the Oenococcus oeni and generates a decarboxylation, transforming malic acid into lactic acid. From the chemical point of view, due to the action of the malolactic enzyme, a carboxyl group is released from the malic acid, thus obtaining lactic acid.

This process itself entails the reduction of acidity, increasing the pH to some extent..

This is a vital process in winemaking, as it contributes to improving its qualities in various aspects. Apart from reducing the acidity of the wine and improving its flavor, it helps to tone the color and also its smell. An example of the latter are the famous dairy-scented wines..

The Oenococcus oeni It is a bacterium that, far from being harmful to humans, has proven to be very useful in the wine industry. However, there are many unknowns that it still contains, so the investigation process on it has not yet concluded.


  1. Achieving succesful malolactic fermentation. Retrieved from: awri.com.au
  2. Bordons, A. and Reguant, C. (2013). Biochemistry of wine lactic acid bacteria and malolactic fermentation. Obtained from: acenología.com
  3. Liu, L., Peng, S., Zhao, H., Wang, Y. Li, H. and Wang, H. (2017, June). Oenococcus oeni: The manin lactic acid bacteria involved in wine - making. Advances in Biotechnology & Microbiology. 4 (1).
  4. Liu, S. (2002). Malolactic fermentation in wine - beyond deacidification. Journal of Applied Microbiology.
  5. Oenococcus oeni. Retrieved from: wineserver.ucdavis.edu
  6. Oenococcus oeni - interest in wine production: quantitative culture and molecular detection. Retrieved from: ivami.com
  7. Oenococcus oeni. Retrieved from: microbewiki.com
  8. Reguant, C., Olguín, N., Bordas, M., Rozes, N. and Bordons, A. (2010). New challenges for Oenococcus oeni as a consequence of climate change. Obtained from: acenología.com

Yet No Comments