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Team:Groningen/Template/MODULE/home/overview/overview2
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Figure 4:
Lactococcus lactis
Lactococcus lactis
Lactococcus lactis is well-known in basic microbiology, genetics, molecular biology, as well as in food science and biotechnology. Lactococcus lactis, is currently very important for industrial fermentations, especially dairy products. In 1909 this bacterium became also known as Streptococcus lactis. And only until recently it was renamed and clearly separated from the genera of streptococci again1.
Food approved
L. lactis is generally known to be safe for human consumption2, and they have never been identified as causes of infectious disease. Because of this fact, this bacterium is used in large quantities in the dairy industries in the production of many different products like cheese.
Characteristics
L. lactis is gram-positive bacterium with non-motile, round-shaped cells and does not form spores. Depending on their growth conditions they typically appear to be 0.5-1.5µm in size. A characteristic of the L. lactis that make them different then and members of the Streptococcus genus, is that these species grown in pairs or in short chains, unlike the long chains that the Streptococcus species form.
Lactococci are found associated with plant material, mainly grasses, from which they are easily inoculated into milk. In order to be able to grown inside dairy products L. lactis relies on the degradation of dairy proteins into peptides. This bacterium uses enzymes to degrade the proteins to produce energy molecules (ATP) from lactose (or other dairy proteins). The byproduct of this process, lactic Acid, is very important in fermentation and for cheese production. Also the lactic acid produced by the bacterium lowers the pH of the product and preserves it from the growth by unwanted bacteria and molds2.
Furthermore L. lactis is capable of producing nisin, an antibiotic-like substance, called a bacteriocin. It is a natural antimicrobial agent with activity against a wide variety of Gram-positive bacteria, including food-borne pathogens such as Listeria, Staphylococcus and Clostridium by targeting the cell membrane. Nisin is a natural preservative present in cheese and it is also used as a preservative in heat processed and low pH foods3.
