OENOCOCCUS OENI: CHARACTERISTICS, MORPHOLOGY, APPLICATIONS - BIOLOGY - 2025

The Oenococcus oeni is a gram positive bacterium that is highly resistant to extreme conditions such as high concentrations of alcohol and acid 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 bacterium Oenococcus oeni is one of the most representative examples of the use that can be given to non-pathogenic microorganisms for the benefit of man.

Taxonomy

The taxonomic classification of this bacterium is as follows:

Domain: Bacteria

Phylum: Firmicutes

Class: Bacilli

Order: Lactobacillales

Family: Leuconostocaceae

Genus: Oenococcus

Species: Oenococcus oeni.

Morphology

Oenococcus oeni is a bacterium that has an ellipsoidal shape, it has an average size of 0.5-0.7 microns in diameter. When observing them 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 1,691 genes that code for the expression of proteins.

characteristics

It is gram positive

Thanks to the thick peptidoglycan cell wall that Oenococcus oeni cells possess, when subjected to the Gram staining process, they retain dye particles. 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 (H ₂ O ₂) molecule in water and oxygen.

It is facultative anaerobic

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

It is heterofermentative

This bacteria 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

Oenococcus oeni reproduces through the asexual reproductive 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 up to 3 and ethanol concentrations higher than 10%.

It is not sporulated

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

Habitat

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 ⁺², Mn ⁺², Na ⁺ and K ⁺.

Carries out malolactic fermentation

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 carry out 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

Applications

Oenococcus oeni 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 is carried out, called malolactic fermentation.

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

This is where the Oenococcus oeni enters 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.

Oenococcus oeni 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.

References

1. Achieving succesful malolactic fermentation. Retrieved from: awri.com.au
2. Bordons, A. and Reguant, C. (2013). Biochemistry of lactic acid bacteria in wine 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