Characterization and probiotic potential of Lactobacillus plantarum strains isolated from cheeses
Highlights
► Lactobacillus plantarum cheese strains evaluated for probiotic potential. ► Choice of 25 strains after screening based on the presence of msa and bsh genes. ► In vitro and in vivo analysis to assess strains probiotic properties. ► Considerable heterogeneity was found among L. plantarum strains. ► Three strains would be candidates as starter cultures for probiotic fermented foods.
Introduction
Probiotics are non-pathogenic microorganisms that, when ingested in adequate amounts, exert a positive influence on their host’s health (FAO/WHO, 2006). A variety of microorganisms, typically food grade lactic acid bacteria (LAB), have been evaluated for their probiotic potential and are applied as adjunct cultures in various types of food products or in therapeutic preparations (Rodgers, 2008). Within the genus Lactobacillus, Lactobacillus plantarum is a member of the facultatively heterofermentative group of lactobacilli. It is a heterogeneous and versatile species that is encountered in a variety of environmental niches, including dairy, meat, fish, and many vegetable or plant fermentations. L. plantarum strains have also been found in many cheese varieties. Moreover, strains of L. plantarum have proven ability to survive gastric transit and colonize the intestinal tract of humans and other mammals (De Vries et al., 2006, Mathara et al., 2008, Georgieva et al., 2009). Various special therapeutic or prophylactic properties have been associated with L. plantarum, such as reduced incidence of diarrhea in daycare centers, reduced pain and constipation associated with irritable bowel syndrome, reduced bloating, flatulence, ability to displace enteropathogens from Caco-2 cells, and capacity to exert positive effect on immunity in HIV+ children (Parvez et al., 2006, Candela et al., 2008).
The available genome sequence of L. plantarum WCSF1, which has been sequenced and annotated (Kleerebezem et al., 2003), generated a major advantage for molecular investigation of this bacterium’s behavior in the GIT and its potential probiotic features.
Although the selection criteria for probiotic strains for humans should include a human origin, currently many non-starter LAB (NSLAB) such as L. paracasei and L. plantarum, which constitute the majority of NSLAB found in most ripened cheese varieties (Pisano et al., 2008), are used in commercial probiotic products. Among industrially used probiotics, selected L. plantarum strains are available in the market (De Vries et al., 2006). The search for strains which show resistance to biological barriers of the human GIT, and which possess physiological characteristics compatible with probiotic properties among LAB isolated from food, may eventually lead to the finding of new probiotic strains for functional food products (Bude-Ugarte et al., 2006).
As part of the selection of new probiotic candidates, 98 L. plantarum strains, isolated within the numerically predominant cultivable species from Italian and Argentinean cheeses and genotypically biodiverse, were subjected to a series of in vitro (following FAO/WHO guidelines, 2006) and in vivo analyses to assess their probiotic properties.
Section snippets
Bacterial strains, yeast cells, culture media, and growth conditions
Ninety-eight L. plantarum strains isolated from Italian and Argentinean cheeses were included in this study. The type strain ATCC 14917T and the strain LMG 9211 were obtained from the American Type Culture Collection (Rockville, MD) and the Laboratory of Microbiology of Gent University (Gent, Belgium), respectively and were reactivated overnight at 30 °C in MRS (Merck, Darmstadt, Germany) broth. Saccharomyces cerevisiae was grown overnight in TSB (Tryptone Soya Broth, Oxoid, Basingstoke,
Preliminary strain selection
Ninety-eight L. plantarum strains, identified on the basis of species-specific PCR for L. plantarum group described by Torriani et al. (2001), with different M13 PCR fingerprinting profiles (Rossetti and Giraffa, 2005) (data not shown) and coming from different Italian and Argentinean cheeses, were searched for the presence of msa and bsh genes, that are considered to be associated with probiotic features. Twenty-five (Table 1) out of the 98 strains tested showed the expected amplicons for both
Discussion
Several functional attributes have already been demonstrated for L. plantarum strains isolated from fermented foods (Adlerberth et al., 1996, Cebeci and Gürakan, 2003, Nguyen et al., 2007, Vizoso-Pinto et al., 2006, Fuentes et al., 2008, Georgieva et al., 2008, Mathara et al., 2008, Pisano et al., 2008, Belviso et al., 2009). In view of the role that L. plantarum plays in food systems, the aim of this work was to select potentially probiotic L. plantarum strains from a wide collection of dairy
Acknowledgements
This work was supported by partial grants from ASER/COL-MIA Project (D.M. MIPAF 16101/7301/08). Collaboration with INLAIN was possible thanks to CNR funding of the Research Project “Lactobacillus plantarum: potential use as probiotic candidate for functional foods and its resistance to phage infection in plants” within the bilateral scientific cooperation Italy-Argentina 2007–2008.
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