Abstract
The aim of the present study was to evaluate the probiotic potential of lactic acid bacteria (LAB) isolated from Greek traditional fermented products. A series of In vitro tests that included survival in simulated gastrointestinal conditions (resistance to low pH, bile salts resistance and bile salts hydrolysis) and safety assessment (resistance to antibiotics, haemolytic and antimicrobial activity) were performed to select potential probiotic candidates, while Lactobacillus rhamnosus GG and Lactobacillus casei Shirota were used as reference strains. Initially, a total of 255 isolates of LAB have been recovered and screened for their survival in simulated gastrointestinal tract conditions and 133 isolates that exhibited moderate or good behavior in these tests were subsequently differentiated and characterized at species level with molecular tools. Pulsed Field Gel Electrophoresis was applied for strain differentiation, while species differentiation was based on restriction analysis of the amplified 16S rRNA gene. Specific multiplex PCR assay targeting the recA genes was applied to resolve the species level of the isolates, belonged to Lb. plantarum group. From the 133 isolates, 47 different strains were recovered and were assigned to Lactobacillus sakei(14), Lactobacillus curvatus (4), Leuconostoc mesenteroides (4), Lactococcus lactis (4), Lactobacillus casei group (1), Lactobacillus brevis (1), Lb. plantarum (10), Lb. pentosus (7) and Lb. paraplantarum (2). The identified strains with good behavior to the gastrointestinal tract tests were selected and further evaluated for their safety aspect. In conclusion, 19 out of the 47 identified strains were assessed as well-behaved, under simulated gastrointestinal conditions and also considered as safe, possessing thus desirable In vitro probiotic properties similar or better to that of the reference strains. These strains may be considered as good candidates for further investigation at in vivo and in situ studies to assess their potential health benefits and their performance as novel probiotic starters or adjunct cultures.
Highlights
The term probiotic is a quite new word meaning “for life” and it is recently used to name bacteria related with positive effects for humans [1] and animals [2]
A generally accepted definition of probiotics recognized by the FAO/WHO, proposes that probiotics are “live microorganisms, which when consumed in adequate amounts, confer a health effect on the host” [3]
The cluster analysis of PFGE SmaI digestion fragments of the lactic acid bacteria (LAB) isolates showed two major clusters as it seen on Figure 1
Summary
The term probiotic is a quite new word meaning “for life” and it is recently used to name bacteria related with positive effects for humans [1] and animals [2]. Several beneficial functions have been suggested for probiotic bacteria e.g., vitamin production [7], cholesterol lowering [8], alleviation of lactose intolerance [9], cancer prevention [10], stimulation of the immune system [11], enhancement of bowel motility [12], relief from constipation [13], prevention and reduction of rotavirus and antibiotic associated diarrhea [14] Some of these benefits have been proved and established, while other have shown a promising potential in animal models, with human clinical studies required to confirm these claims [15]. It’s of great importance to mention that the biological effects revealed from probiotic bacteria are strain specific and there is no universal strain that would provide all the suggested benefits, not even strains of the same species [15]
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