Lactococcus lactis is classified as a gram-positive, spherical, homolactate, non-sporulating, and facultative anaerobic gut bacterium. It originates from the streptococcus genus and re-classified into the Lactococcus genus in 1985. They are known as homofermenters, meaning that they produce a single product, lactic acid in this case, as the primary or only product of glucose fermentation.
Lactococcus lactis has been used for centuries in the fermentation of food, especially cheese, yogurt, sauerkraut and the like, thereby rendering it is generally recognized as safe (GRAS) status by the Food and Drug Administration (FDA). Apart from imparting flavor, L. lactis, as a lactic acid bacteria (LAB), also produces acid which preserves food. Some strains further enhance this preservation property with the production of bacteriocins, thus reinforcing its role in the food industry. Other than its important function in food, L. lactis has become the model LAB when it comes to genetic engineering. Lactococci are currently being used in the biotechnology industry. They are easily grown at the industrial scale on whey-based media.