**2. Lactic acid bacteria used in dairy industry**

Lactic acid bacteria (LAB) comprise different groups of microorganisms, such as *Carnobacterium*, *Enterococcus*, *Tetragenococcus*, *Vagococcus*, *Weissella* as well as species of genera which constitute the "industrial" core of LAB, like *Lactococcus, Lactobacillus*, *Streptococcus*, *Pediococcus* and *Leuconostoc* [6]. LAB reside in different natural habitats, including healthy and decaying plants, milk and dairy products, oral cavity and gastrointestinal tract of humans and animals. In addition, lactic acid bacteria can grow on meat and wine. These features are used in the production of fermented sausages (*Lactobacillus*, *Pediococcus*) and to improve the organoleptic characteristics of wine (*Oenococcus oeni*) [6].

Lactic Acid Bacteria Resistance to Bacteriophage and Prevention Techniques

*Lactococcus lactis* subsp. *lactis*, *Lactococcus lactis* subsp.

*Lactococcus lactis* subsp. *lactis*, *Lactococcus lactis* subsp.

*Lactococcus lactis* subsp*. lactis, Lactococcus lactis* subsp*.* 

*Lactococcus lactis* subsp*. lactis* var*. diacetylactis Leuconostoc mesenteroides* subsp*. cremoris*

*Lactobacillus acidophilus, Streptococcus thermophilus* 

*Lactobacillus rhamnosus, Lactobacillus acidophilus* 

*Lactococcus lactis* subsp*. lactis* var*. diacetylactis* 

*Lactobacillus helveticus, Lactobacillus delbrueckii* subsp*. lactis* 

*Lactococcus lactis* subsp. *lactis* var. *diacetylactis*, *Leuconostoc mesenteroides* subsp. *cremoris Leuconostoc mesenteroides* subsp. *mesenteroides*

*Lactococcus lactis* subsp. *lactis* var. *diacetylactis*

enveloped in a protein structure (capsid). Current taxonomy and classification of bacteriophages rely on the type of nucleic acid genome and phage morphology, physiology (temperate and virulent life cycles) and genomics. Taxonomy of viruses is supervised by the International Committee for Taxonomy of Viruses (ICTV) that imposes rules for names and

Yoghurt *Streptococcus thermophilus, Lactobacillus delbrueckii* subsp.

*Streptococcus thermophilus*\* Tvarog, blue cheese *Lactococcus lactis* subsp. *lactis*, *Lactococcus lactis* subsp.

*bulgaricus* 

*cremoris*

*cremoris*

*cremoris*

*cremoris* 

*bulgaricus* 

*cremoris* 

Cheddar, Feta *Lactococcus lactis* subsp*. lactis, Lactococcus lactis* subsp*.* 

Mozzarella, Pizza cheese *Streptococcus thermophilus, Lactobacillus delbrueckii subsp.* 

*Streptococcus thermophilus* 

Swiss, Grana *Lactobacillus helveticus, Lactobacillus delbrueckii* subsp*. lactis* 

Actimel®-like products *Lactobacillus casei, Lactobacillus paracasei* subsp*. paracasei* 

Swiss, Italian *Lactococcus lactis* subsp*. lactis, Lactococcus lactis* subsp*.* 

*cremoris* 

**Table 1.** Various dairy products and LAB species applied in their production.

\* seldom applied in cottage cheese, \*\* texturizing strains

Ryazanka *Streptococcus thermophilus*\*\*

writings.

Pasta Filata

butter

beverages

milk beverages

Cottage cheese, Cheddar,

Butter milk, fermented cream,

Masdamer, Gouda, Edam, Tilsitter, soft mould ripened cheese, quark, fermented milk

Mozzarella, Swiss, stabilized soft mould ripened cheese

Fermented cream, fermented

**Product LAB species**

to Lower Phage Contamination in Dairy Fermentation 25

The genus *Lactococcus* is the best characterized food-related LAB. As lactococcal strains are able to grow in milk and transform lactose to lactic acid, they are commonly used as starter cultures in industrial fermentations for cheese production. The ability of LAB to transform raw milk into other products suitable for consumption has been used by man for millenniums. Such long history record of interactions of man with lactic acid bacteria and present knowledge led to assigning these bacteria the GRAS status (generally recognized as safe) [7]. Dairy products and the respective LAB species are gathered in Table 1 based on specifications and recommendations released by the main culture suppliers.

A typical lactococcal mixed starter culture consists of 2-3 well defined strains, which specific properties have significant impact on the texture and flavor of the end product. Nowadays, large dairy plants process up to 106 liters of milk per day, producing annually approximately 107 tons of cheese [8]. Therefore, technological problems in production of cottage and hard cheeses caused by bacteriophage infections have serious economical consequences.
