Abstract
Dairy propionibacteria are used as cheese ripening starters, as biopreservative and as beneficial additives, in the food industry. The main species, Propionibacterium freudenreichii, is known as GRAS (Generally Recognized As Safe, USA, FDA). In addition to another dairy species, Propionibacterium acidipropionici, they are included in QPS (Qualified Presumption of Safety) list. Additional to their well-known technological application, dairy propionibacteria increasingly attract attention for their promising probiotic properties. The purpose of this review is to summarize the probiotic characteristics of dairy propionibacteria reported by the updated literature. Indeed, they meet the selection criteria for probiotic bacteria, such as the ability to endure digestive stressing conditions and to adhere to intestinal epithelial cells. This is a prerequisite to bacterial persistence within the gut. The reported beneficial effects are ranked according to property’s type: microbiota modulation, immunomodulation, and cancer modulation. The proposed molecular mechanisms are discussed. Dairy propionibacteria are described as producers of nutraceuticals and beneficial metabolites that are responsible for their versatile probiotic attributes include short chain fatty acids (SCFAs), conjugated fatty acids, surface proteins, and 1,4-dihydroxy-2-naphtoic acid (DHNA). These metabolites possess beneficial properties and their production depends on the strain and on the growth medium. The choice of the fermented food matrix may thus determine the probiotic properties of the ingested product. This review approaches dairy propionibacteria, with an interest in both technological abilities and probiotic attributes.
Highlights
Propionibacteria are high-GC content, non-motile, non-spore forming, anaerobic to aerotolerant, gram-positive bacteria, which belong to the actinomycetales order
The administration of cheeses matrix containing P. freudenreichii, alone or in combination with lactic acid bacteria, was shown to increase Pparg mRNA levels in the colon of mice during trinitrobenzene sulfonic acid (TNBS)-induced colitis [7,12]. This effect could be attributed to the presence of Conjugated fatty acids (CFAs) in fermented cheeses, but additional analysis is required to establish a link between the increase of Pparg gene expression and CFA production by dairy propionibacteria
In vitro and in vivo studies showed the anti-proliferative effect of conjugated fatty acids, including those produced by dairy propionibacteria [84,86,87,88,89], on various cancerous cells such as melanoma, colorectal, breast, prostate and hepatoma cell lines [92]
Summary
Propionibacteria are high-GC content, non-motile, non-spore forming, anaerobic to aerotolerant, gram-positive bacteria, which belong to the actinomycetales order. They are highly distinct from low GC content firmicutes, which include lactic acid bacteria. Actinomycetales comprise bacterial species with a mycelium-like aspect, found in various environments, including animal hosts and soil, and are known for a prolific production of small molecules, including antimicrobials. The genus Propionibacterium comprises both cutaneous species (including the well-known P. acnes), which may act as opportunistic pathogens, and dairy species, which have no reported adverse effects. The dairy species Propionibacterium freudenreichii and Propionibacterium acidipropionici are clearly distinct from cutaneous species. Dairy species are presented in green and cutaneous ones in red
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