Abstract
In this study, twelve strains of Lactobacillus plantarum derived from spontaneously fermented vegetables (carrots and beetroot) and traditionally prepared sauerkraut were compared for their potential probiotic abilities with seven Lactobacillus rhamnosus strains of human origin. The tested strains were investigated for some technological properties and in vitro functional characteristics for potential probiotic strains. Selection probiotic criteria included the ability of the strains to withstand conditions similar to the digestive tract, antimicrobial activity against a wide range of intestinal pathogens and sensitivity to antibiotics. The total acidity in milk was generally higher in intestinal strains in relation to plant strains. The ability of the tested strains to survive simulated gastric conditions showed a greater resistance of the human strains at a low pH 2.5 and the presence of pepsin, while in the presence of bile salts and pancreatin, some intestinal strains were more sensitive compared to plant strains. A wide spectrum of antimicrobial activities was observed in all tested strains. Most of the plant strains were resistant to aminoglycosides and vancomycin but sensitive to ampicillin and penicillin, while only some intestinal strains were resistant to these drugs.
Highlights
Probiotic refers to live microorganisms which, when administrated in adequate amounts, confer a health benefit on the host (FAO, 2006)
Comparing the growth at different temperatures, it was observed that all the isolates from fermented vegetables grew at 15 and 30°C, while two human isolates, TMFM and TMFV, showed an ability to grow at 45°C as well as to survive at 60°C (Table 1), which proved them to be good candidates for food application
The total acidity in milk was generally higher in the intestinal L. rhamnosus strains in relation to L. plantarum strains from fermented vegetables, while all tested isolates showed coagulation, acidification and reduction of litmus milk (Table 1)
Summary
Probiotic refers to live microorganisms which, when administrated in adequate amounts, confer a health benefit on the host (FAO, 2006). The health benefits associated with the ingestion of probiotic bacteria include a reduction in colon irritation and constipation, treatment of acute rotavirus diarrhea, inhibition antagonism towards intestinal pathogens, synthesis of B vitamins, lactose maldigestion, cholesterol absorption and inhibition of tumor formation (Ziemer and Gibson, 1998). The absence of pathogenicity, the ability to adhere to the gastrointestinal mucosa and the competitive exclusion of pathogens are criteria that have been used for the selection of probiotics (Ouwehand et al, 2004). The mechanism through which probiotics may antagonize pathogens involves the production of antimicrobial compounds such as lactic acid, acetic acid, hydrogen peroxide and bacteriocins. Lactobacillus spp. have GRAS (generally recognized as safe) status, because of their long and safe use in food fermentation, it is necessary to confirm the safety of these microorganisms in-
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