Lactococcus lactis

Lactococcus lactis is a Gram-positive lactic acid bacterium used in dairy fermentation and as a production host for nisin, an antimicrobial peptide.

Lactic acid fermentation: An anaerobic metabolic process that converts sugars into lactic acid and regenerates NAD+. Lactococcus lactis uses this pathway to acidify milk during fermentation.
Cheese: A dairy food made by coagulating milk proteins and separating curds from whey. Lactococcus lactis starter cultures acidify milk and help shape cheese texture and flavor.
Gram-positive bacteria: Bacteria whose cell envelopes retain crystal violet stain and typically have thick peptidoglycan walls. Lactococcus lactis has the thick-walled cell structure that defines this broad bacterial group.
Carl Wilhelm Scheele: An eighteenth-century Swedish chemist who isolated lactic acid from sour milk in 1780. His work helped establish the chemical basis of milk souring that fermentation cultures cause.
Streptococcus thermophilus: A thermophilic lactic acid bacterium widely used in yogurt and some cheese fermentations. It is a common dairy starter with a higher temperature preference than Lactococcus lactis.
Lactose metabolism: The cellular uptake and breakdown of lactose into usable metabolic products. Lactose supplies the fermentable sugar that drives acid production in milk.
Cultured buttermilk: A fermented milk drink produced by bacterial acidification of milk. Lactococcus lactis is among the bacteria used to ferment cultured buttermilk.
Lactococcus: A genus of lactic acid bacteria that includes species used in food fermentation. Lactococcus lactis is the genus’s best-known species in dairy applications.
Louis Pasteur: A French chemist and microbiologist whose work established microorganisms as agents of fermentation and disease. Pasteur’s fermentation research helped frame lactic acid bacteria as active agents in food transformation.
Lactobacillus delbrueckii subsp. bulgaricus: A thermophilic lactic acid bacterium used with Streptococcus thermophilus to ferment yogurt. Its yogurt partnership contrasts with Lactococcus lactis’s familiar role in mesophilic dairy fermentations.

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