Lactococcus lactis
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| Lactococcus lactis | ||||||||||||||
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| Lactococcus lactis (Lister 1873) Schleifer et al. 1986 |
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L. l. cremoris |
Lactococcus lactis is a Gram-positive bacteria used extensively in the production of buttermilk and cheese.[1] L. lactis are cocci that group in pairs and short chains,and depending on growth conditions appears ovoid with typically 0.5 - 1.5 µm in length. L. lactis do not produce spores (non-sporulating) and are not motile (non-motile). Cultured in the laboratory, L. lactis colonies appear bright orange on nutrient agar. They have a homo-fermentative metabolism and have been reported to produce exclusively L(+) lactic acid [2]. However, [3] reported that D(-) lactic acid can be produced when cultured at low pH. The capability to produce lactic acid is one of the reasons why Lactococcus lactis is one of the most important micro-organisms involved in the dairy industry[4]. Generally, it has been considered as an oportunistic pathogen [5]. Even though, the number of clinical cases associated with infections by these microorganisms has increased in the last decade in both humans and animals[6][7]. L. lactis is a bacterium which has a crucial importance for manufacturing dairy products such as buttermilk, yogurt or cheese. When L. lactis ssp. lactis is added to milk, the bacterium uses enzymes to produce energy molecules, called ATP, from lactose.The byproduct of ATP energy production is lactic acid. The lactic acid produced by the bacterium curdles the milk that then separates to form curds, which are used to produce cheese and whey [8].
Other uses that have been reported for this bacteria include the production of pickled vegetables, beer or wine, some breads and other fermented food-stuffs. Nowadays, researchers believe that understanding the physiology and genetic make-up of this bacterium will provide food manufacturers as well as the pharmaceutical industry with invaluables benefits [9][10]
[edit] Cheese production
L. lactis subsp. lactis (formerly Streptococcus lactis[11]) is used in the early stages for the production of many cheeses including Brie, Camembert cheese, cheddar, Colby, Gruyère, Parmesan, and Roquefort.[12]
The use of L. lactis in dairy factories is not without issues. Bacteriophages specific to L. lactis cause significant economic losses each year by preventing the bacteria from fully metabolizing the milk substrate.[12] Several epidemiologic studies showed that the phages mainly responsible for these losses are from the species 936, c2 and P335.[13]
[edit] References
- ^ Madigan M, Martinko J (editors). (2005). Brock Biology of Microorganisms, 11th ed., Prentice Hall. ISBN 0-13-144329-1.
- ^ ROISSART, H. and Luquet F.M. Bactéries lactiques: aspects fondamentaux et technologiques. Uriage, Lorica, France, 1994, vol. 1, p. 605. ISBN 2 9507477 0 1
- ^ AKERBERG, C.; HOFVENDAHL, K.; ZACCHI, G. and HAHN-HAGERDAL, B. Modeling the influence of pH, temperature, glucose and lactic acid concentration on the kinetics of lactic acid production by Lactococcus lactis ssp. lactis ATCC 19435 in whole-wheat flour. Applied Microbiology and Biotechnology, 1998, vol. 49, no. 6, p. 682-690
- ^ http://www.ebi.ac.uk/integr8/QuickSearch.do?action=doOrgSearch&organismName=Lactococcus+lactis
- ^ Aguirre M, Collins MD. Lactic acid bacteria and human clinical infection. J Appl Bacteriol 1993;75:95-107
- ^ Facklam RR, Pigott NE, Collins MD. Identification of Lactococcus species from human sources. Proceedings of the XI Lancefield International Symposium on Streptococci and Streptococcal Diseases, Siena, Italy. Stuttgart: Gustav Fischer Verlag; 1990:127
- ^ Mannion PT, Rothburn MM. Diagnosis of bacterial endocarditis caused by Streptococcus lactis and assisted by immunoblotting of serum antibodies. J Infect 1990;21:317-8
- ^ http://www.ebi.ac.uk/2can/genomes/bacteria/Lactococcus_lactis.html
- ^ http://www.genoscope.cns.fr
- ^ Steidler L, Rottiers P., Therapeutic drug delivery by genetically modified Lactococcus lactis, Ann N Y Acad Sci 2006; 1072, 176-186
- ^ Chopin MC, Chopin A, Rouault A, Galleron N (1989). "Insertion and amplification of foreign genes in the Lactococcus lactis subsp. lactis chromosome" (PDF). Appl. Environ. Microbiol. 55 (7): 1769-74. PMID 2504115.
- ^ a b Coffey A, Ross RP (2002). "Bacteriophage-resistance systems in dairy starter strains: molecular analysis to application". Antonie Van Leeuwenhoek 82 (1–4): 303-21. doi:. PMID 12369198.
- ^ Madera C, Monjardin C, Suarez JE (2004). "Milk contamination and resistance to processing conditions determine the fate of Lactococcus lactis bacteriophages in dairies" (PDF). Appl Environ Microbiol 70 (12): 7365–71. doi:. PMID 15574937.
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