Probiotics have been defined by The Food Agricultural Organization/World Health Organization (FAO/WHO) as "live microorganisms which when administered in adequate amounts confer a health benefit on the host" [1]. Probiotic bacteria not only have to be safe but also have to survive in the gastrointestinal tract conditions and possess beneficial properties [1]. Food supplemented with probiotics is preferable for consumers than supplementation with capsules, tablets and other drug forms. Food has buffering properties and may maintain the survival of probiotic bacteria during passage through the gut [2]. Moreover, strains with strong functional properties including antioxidant and antimicrobial activity would be desirable for developing novel functional food supplemented with probiotic microorganisms. However, due to different probiotic bacteria properties, one of the most essential factors are the selection of the proper cultures [3]. The evaluation of potential probiotic bacteria for probiotic properties with the potential application for functional products as supplements is growing nowadays [4,5].
The aim of this study was to evaluate probiotic characteristics in vitro such as resistance to low pH and bile salts and antioxidant activity of commercially available strains belonging to Lactobacillus and Bifidobacterium genera.
The in vitro resistance of 9 Lactobacillus and 5 Bifidobacterium spp. to low pH and bile salts were investigated. Most of tested bacteria were able to tolerate pH 3 for 4 h, while in pH 2 for 4 h survived 8 of 14 strains. Bifidobacterium pseudolongum DSM 20099, Bifidobacterium animalis DSM 20105 showed resistance to pH 2 for 4 h. The antioxidant activity of probiotic bacteria intact cell and intracellular cell-free extract was determined by 1-diphenyl-2-picrylhydrazyl (DPPH) and 2-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS) radical scavenging assays. The results showed that antioxidant activity varied among the different strain of tested probiotics. Intact cells and cell-free extracts of L. reuteri DSM 20015 and L. paracasei subsp. paracasei DSM 4905 exhibited the highest DPPH radical scavenging activity, while the highest ABTS radical scavenging activity was exhibited by intact cells and intracellular cell-free extract of B. longum subsp. infantis DSM 20088. However, these strains were sensitive to low pH. Results suggest that probiotic bacteria which survive in low pH could be suitable candidates for food production, while other strains should be protected with specific vehicle.