Enterococci from Raw-Milk Cheeses: Current Knowledge on Safety, Technological, and Probiotic Concerns

Abstract

The present study is focused on the safety, technological characteristics, and probiotic evaluation of Enterococcus species from different artisanal raw milk dairy products, mainly cheeses with ripening. Apart from proteolytic and lipolytic activities, most enterococci show the ability to metabolize citrate and convert it to various aromatic compounds. Long-ripened cheeses therefore have a specific flavor that makes them different from cheeses produced from thermally treated milk with commercial starter cultures. In addition, enterococci are producers of bacteriocins effective against spoilage and pathogenic bacteria, so they can be used as food preservatives. However, the use of enterococci in the dairy industry should be approached with caution. Although originating from food, enterococci strains may carry various virulence factors and antibiotic-resistance genes and can have many adverse effects on human health. Still, despite their controversial status, the use of enterococci in the food industry is not strictly regulated since the existence of these so-called desirable and undesirable traits in enterococci is a strain-dependent characteristic. To be specific, the results of many studies showed that there are some enterococci strains that are safe for use as starter cultures or as probiotics since they do not carry virulence factors and antibiotic-resistance genes. These strains even exhibit strong health-promoting effects such as stimulation of the immune response, anti-inflammatory activity, hypocholesterolemic action, and usefulness in prevention/treatment of some diseases.

Dairy Products: A Potential Source of Multidrug-Resistant Enterococcus faecalis and Enterococcus faecium Strains

“…One of the main genera of the lactic acid bacteria (LAB) group is Enterococcus , comprising over 50 gram-positive species. They are found in a variety of environments, such as the human gastrointestinal tract, animals, plants, soil and water [ 1 ]. They can also appear in food of animal origin such as raw meat, fermented sausages and cheeses [ 2 ].…”

“…For this reason, they are found in both raw and pasteurized milk [ 3 ]. Traditionally, in the south and north of Europe they are used as starter cultures to make various, mainly artisanal, cheeses from raw and pasteurized milk [ 1 , 3 ]. Enterococci are a standard element of the non-starter LAB used to produce traditional Mediterranean, Western Balkan countries and Brazilian cheeses from raw milk of sheep, goats and cows [ 1 ].…”

“…Traditionally, in the south and north of Europe they are used as starter cultures to make various, mainly artisanal, cheeses from raw and pasteurized milk [ 1 , 3 ]. Enterococci are a standard element of the non-starter LAB used to produce traditional Mediterranean, Western Balkan countries and Brazilian cheeses from raw milk of sheep, goats and cows [ 1 ]. Enterococci also still play an important role in the production of fermented dairy products, such as some cheeses, in extension of the shelf life and improvement of their taste, texture, and aroma [ 4 ].…”

Causality Verification for the Correlation between the Presence of Nonstarter Bacteria and Flavor Characteristics in Soft-Type Ripened Cheeses

“…and Enterococcus sp., which are known as NSLAB, have been reported in a few previous studies. Enterococci can degrade citrate into various aromatic compounds, such as acetate ( 26 ). Carnobacterium maltaromaticum isolated from milk produces 3-methylbutanal, 2-methylbutanal, and 2-methylpropanal ( 27 , 28 ).…”

A Lactic Acid Bacteria Consortium Impacted the Content of Casein-Derived Biopeptides in Dried Fresh Cheese

“…Recently Papadimitriou et al [ 21 ] emphasised important technological properties, including proteolytic potential and bacteriocin production of E. faecalis PK23, isolated from autochthonous white brine cheese, which is, like E. faecium strains, often neglected due to safety concerns. The E. faecium ZGZA7-10 strain was previously isolated from fresh soft cheese from the Zagorje region in Croatia where, as well as in Southern Europe, artisanal cheeses may contain up to 10 7 CFU/g enterococci at the end of cheese ripening, thereby contributing to their typical sensory properties [ 14 , 15 , 22 ]. This is consistent with studies in which E. faecium and E. faecalis were reported as the most prevalent species of Enterococcus genus among raw milk and dairy products microbiota [ 14 , 15 , 23 , 24 , 25 ].…”