Lactococcus
Encyclopedia
Lactococcus is a genus
of lactic acid bacteria
that were formerly included in the genus Streptococcus Group N1. They are known as homofermentors meaning that they produce a single product, lactic acid
in this case, as the major or only product of glucose
fermentation
. Their homofermentative character can be altered by adjusting cultural conditions like pH
, glucose concentration, and nutrient limitation. They are gram-positive
, catalase
-negative, non-motile cocci that are found singly, in pairs, or in chains. The genus contains strains known to grow at or below 7˚C.
Five species of Lactococcus are currently recognized along with three subspecies. They are:
These organisms are commonly used in the dairy industry in the manufacture of fermented dairy products like cheeses. They can be used in single-strain starter cultures, or in mixed-strain cultures with other lactic acid bacteria such as Lactobacillus
and Streptococcus
. Special interest is placed on the study of L. lactis subsp. lactis and L. lactis subsp. cremoris, as they are the strains used as starter cultures in industrial dairy fermentations. Their main purpose in dairy production is the rapid acidification of milk; this causes a drop in the pH of the fermented product, which prevents the growth of spoilage bacteria. The bacteria also play a role in the flavor of the final product.
Lactococci are currently being used in the biotechnology
industry. They are easily grown at industrial scale up on cheap whey-based media. As food-grade bacteria, they are used in the production of foreign proteins that are applied to the food industry.
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
of lactic acid bacteria
Lactic acid bacteria
The lactic acid bacteria comprise a clade of Gram-positive, low-GC, acid-tolerant, generally non-sporulating, non-respiring rod or cocci that are associated by their common metabolic and physiological characteristics. These bacteria, usually found in decomposing plants and lactic products, produce...
that were formerly included in the genus Streptococcus Group N1. They are known as homofermentors meaning that they produce a single product, lactic acid
Lactic acid
Lactic acid, also known as milk acid, is a chemical compound that plays a role in various biochemical processes and was first isolated in 1780 by the Swedish chemist Carl Wilhelm Scheele. Lactic acid is a carboxylic acid with the chemical formula C3H6O3...
in this case, as the major or only product of glucose
Glucose
Glucose is a simple sugar and an important carbohydrate in biology. Cells use it as the primary source of energy and a metabolic intermediate...
fermentation
Fermentation (biochemistry)
Fermentation is the process of extracting energy from the oxidation of organic compounds, such as carbohydrates, using an endogenous electron acceptor, which is usually an organic compound. In contrast, respiration is where electrons are donated to an exogenous electron acceptor, such as oxygen,...
. Their homofermentative character can be altered by adjusting cultural conditions like pH
PH
In chemistry, pH is a measure of the acidity or basicity of an aqueous solution. Pure water is said to be neutral, with a pH close to 7.0 at . Solutions with a pH less than 7 are said to be acidic and solutions with a pH greater than 7 are basic or alkaline...
, glucose concentration, and nutrient limitation. They are gram-positive
Gram-positive
Gram-positive bacteria are those that are stained dark blue or violet by Gram staining. This is in contrast to Gram-negative bacteria, which cannot retain the crystal violet stain, instead taking up the counterstain and appearing red or pink...
, catalase
Catalase
Catalase is a common enzyme found in nearly all living organisms that are exposed to oxygen, where it catalyzes the decomposition of hydrogen peroxide to water and oxygen...
-negative, non-motile cocci that are found singly, in pairs, or in chains. The genus contains strains known to grow at or below 7˚C.
Five species of Lactococcus are currently recognized along with three subspecies. They are:
- L. lactisLactococcus lactisLactococcus lactis is a Gram-positive bacterium used extensively in the production of buttermilk and cheese, but has recently also become famous as the first genetically modified organism to be used alive for the treatment of human disease. L...
- L. lactisLactococcus lactisLactococcus lactis is a Gram-positive bacterium used extensively in the production of buttermilk and cheese, but has recently also become famous as the first genetically modified organism to be used alive for the treatment of human disease. L...
subsp. lactis - L. lactis subsp. cremoris
- L. lactis subsp. hordniae
- L. lactis
- L. garvieae
- L. plantarum
- L. raffinolactis
- L. piscium
These organisms are commonly used in the dairy industry in the manufacture of fermented dairy products like cheeses. They can be used in single-strain starter cultures, or in mixed-strain cultures with other lactic acid bacteria such as Lactobacillus
Lactobacillus
Lactobacillus is a genus of Gram-positive facultative anaerobic or microaerophilic rod-shaped bacteria. They are a major part of the lactic acid bacteria group, named as such because most of its members convert lactose and other sugars to lactic acid. They are common and usually benign...
and Streptococcus
Streptococcus
Streptococcus is a genus of spherical Gram-positive bacteria belonging to the phylum Firmicutes and the lactic acid bacteria group. Cellular division occurs along a single axis in these bacteria, and thus they grow in chains or pairs, hence the name — from Greek στρεπτος streptos, meaning...
. Special interest is placed on the study of L. lactis subsp. lactis and L. lactis subsp. cremoris, as they are the strains used as starter cultures in industrial dairy fermentations. Their main purpose in dairy production is the rapid acidification of milk; this causes a drop in the pH of the fermented product, which prevents the growth of spoilage bacteria. The bacteria also play a role in the flavor of the final product.
Lactococci are currently being used in the biotechnology
Biotechnology
Biotechnology is a field of applied biology that involves the use of living organisms and bioprocesses in engineering, technology, medicine and other fields requiring bioproducts. Biotechnology also utilizes these products for manufacturing purpose...
industry. They are easily grown at industrial scale up on cheap whey-based media. As food-grade bacteria, they are used in the production of foreign proteins that are applied to the food industry.