Lactococcus lactis
| Lactococcus lactis | ||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
Lactococcus lactis |
||||||||||||
| Systematics | ||||||||||||
|
||||||||||||
| Scientific name | ||||||||||||
| Lactococcus lactis | ||||||||||||
| ( Lister 1873) Schleifer et al. 1986 |
Lactococcus lactis is a gram-positive bacterium that is used to make buttermilk , curdled milk , kefir, and cheese .
features
Appearance
The cells of Lactococcus lactis are cocci that form pairs or short chains and, depending on the growth conditions, appear oval with a length of 0.5 to 1.5 μm. They do not form persistence forms like endospores and are not motile .
Growth and metabolism
The temperature optimum for growth and reproduction for Lactococcus lactis is in the range from 28 to 32 ° C, thus L. lactis is one of the mesophilic organisms. It also grows at 10 ° C, but not at 45 ° C, this is used as a criterion to distinguish it from the more thermophilic species of Streptococcus .
L. lactis carries out a homofermentative lactic acid fermentation and produces L - (+) - lactic acid . At a lower pH , their D form can also be produced. Lactic acid is produced during lactic acid fermentation , in which the bacteria use their enzymes to generate energy by breaking down lactose .
genetics
The genome of several bacterial strains of the species Lactococcus lactis has already been completely sequenced . The size of the genome of all representatives examined so far is between 2370 and 2810 kilobase pairs (kb), which is only 55% of the genome size of Escherichia coli . About 2300-2600 proteins are annotated .
Systematics
External system
Lactococcus is a genus of gram-positive, spherical bacteria. The generic name isalso written as Laktokokkus ( plural : Laktokokken)" Germanized ". Lactococcus is closely related to the genus Streptococcus , both of which belong to the Streptococcaceae family . They usedto be part of the genus Streptococcus - together with the enterococci, which are of fecal origin. In order to avoid the frequently pathogenic species from those which are harmless to humans, and e.g. In1986, to differentiate between speciesalso used in the food industry , they were separated into the genera Streptococcus , Enterococcus and Lactococcus . Together with other types of bacteria, they belong to the order of lactic acid bacteria . However, the old names are still used, for example Streptococcus lactis is the basonym for Lactococcus lactis , as it was originallyassigned tothe genus Streptococcus .
Internal system
Currently (2013) four are Lactococcus lactis subspecies (subspecies) from the Leibniz Institute DSMZ - German Collection of Microorganisms and Cell Cultures in Prokaryotic Nomenclature Up-to-date ( "Prokaryotic Nomenclature up to date") listed. This compilation includes all names validly published according to the Bacteriological Code and takes into account the validation list of the International Journal of Systematic and Evolutionary Microbiology .
-
Lactococcus lactis (Lister 1873) Schleifer et al. 1986, comb. nov. (previously Streptococcus lactis )
- Lactococcus lactis subsp. cremoris (Orla-Jensen 1919) Schleifer et al. 1986, comb. nov. (previously Streptococcus cremoris )
- Lactococcus lactis subsp. hordniae ( Latorre-Guzmán et al. 1977) Schleifer et al. 1986, comb. nov. (previously Lactobacillus hordniae )
- Lactococcus lactis subsp. lactis (Lister 1873) Schleifer et al. 1986, comb. nov. (previously Streptococcus lactis )
- Lactococcus lactis subsp. tructae Pérez et al. 2011, subsp. nov.
Industrial importance
The ability to produce lactic acid is one of the reasons why Lactococcus lactis is one of the most important microorganisms in the manufacture of dairy products . The lactic acid causes the milk to coagulate and enables the curd and whey to be separated . With the help of Lactococcus lactis subsp. lactis , kefir , quark and other cream cheese products are made. Lactococcus lactis subsp. cremoris is in the production of sour milk (sour milk), sour cream products such as sour cream , sour cream butter , buttermilk , cottage cheese and cheese used. Other areas of application for L. lactis in food processing include the production of pickled vegetables , beer, wine and bread.
Furthermore, the preservative nisin is obtained biotechnologically with L. lactis .
The use of L. lactis in dairies is not without its problems. Specific bacteriophages cause considerable economic losses by inhibiting L. lactis .
Individual evidence
- ↑ a b Lactococcus lactis at the European Bioinformatics Institute (EBI) (English) ( Memento from August 19, 2011 in the Internet Archive )
- ↑ a b c d Gunther Müller: Fundamentals of food microbiology . 6th edition. Steinkopff Verlag, Darmstadt 1986, ISBN 3-7985-0673-6 , p. 178 .
- ↑ a b Michael T. Madigan, John M. Martinko, Jack Parker: Brock Mikrobiologie. German translation edited by Werner Goebel. 1st edition. Spektrum Akademischer Verlag GmbH, Heidelberg / Berlin 2000, ISBN 3-8274-0566-1 , pp. 558-563.
- ↑ a b Lactococcus lactis. In: National Center for Biotechnology Information (NCBI) Genome website . Retrieved December 18, 2013 .
- ↑ JP Euzéby, Aidan C. Part: Order Lactobacillales. In: List of Prokaryotic names with Standing in Nomenclature (LPSN) . Retrieved December 18, 2013 .
- ^ JP Euzéby, Aidan C. Parte: Genus Lactococcus. In: List of Prokaryotic names with Standing in Nomenclature (LPSN) . Accessed August 26, 2019 .
- ^ Prokaryotic Nomenclature Up-to-date. In: Website of the Leibniz Institute DSMZ - German Collection of Microorganisms and Cell Cultures GmbH . Retrieved December 18, 2013 .
- ↑ Nisin E234. In: Website Transparency Genetic Engineering (transGEN) . August 26, 2019. Retrieved August 26, 2019 .
- ^ A. Coffey, RP Ross: Bacteriophage-resistance systems in dairy starter strains: molecular analysis to application. In: Antonie van Leeuwenhoek. Volume 82, Numbers 1-4, August 2002, pp. 303-321, ISSN 0003-6072 . PMID 12369198 . (Review).