Characterizing Propionibacterium freudenreichii ssp. shermanii JS and Lactobacillus rhamnosus LC705 as a new probiotic combination: basic properties of JS and pilot in vivo assessment of the combination

<b>Characterizing <i>Propionibacterium freudenreichii </i> ssp. <i>shermanii</i> JS and <i>Lactobacillus rhamnosus</i> LC705 as a new probiotic combination: basic properties of JS and pilot <i>in vivo</i> assessment of the combination</b> Each candidate probiotic strain has to have the documentation for the proper identification with current molecular tools, for the biological properties, for the safety aspects and for the health benefits in human trials if the intention is to apply the strain as health promoting culture in the commercial applications. No generalization based on species properties of an existing probiotic are valid for any novel strain, as strain specific differences appear e.g. in the resistance to GI tract conditions and in health promoting benefits (Madsen, 2006). The strain evaluation based on individual strain specific probiotic characteristics is therefore the first key action for the selection of the new probiotic candidate. The ultimate goal in the selection of the probiotic strain is to provide adequate amounts of active, living cells for the application and to guarantee that the cells are physiologically strong enough to survive and be biologically active in the adverse environmental conditions in the product and in GI tract of the host. The <i>in vivo</i> intervention studies are expensive and time consuming; therefore it is not rational to test all the possible candidates <i>in vivo</i>. Thus, the proper <i>in vitro</i> studies are helping to eliminate strains which are unlikely to perform well <i>in vivo</i>. The aims of this study were to characterize the strains of <i>Propionibacterium freudenreichii</i> ssp. <i>shermanii </i> JS and <i>Lactobacillus rhamnosus</i> LC705, both used for decades as cheese starter cultures, for their technological and possible probiotic functionality applied in a combined culture. The <i>in vitro</i> studies of<i> Propionibacterium freudenreichii</i> ssp. <i>shermanii</i> JS focused on the monitoring of the viability rates during the acid and bile treatments and on the safety aspects such as antibiotic susceptibility and adhesion. The studies with the combination of the strains JS and LC705 administered in fruit juices monitored the survival of the strains JS and LC705 during the GI transit and their effect on gut wellbeing properties measured as relief of constipation. In addition, safety parameters such as side effects and some peripheral immune parameters were assessed. Separately, the combination of <i>P. freudenreichii</i> ssp.<i> shermanii </i>JS and <i>Lactobacillus rhamnosus</i> LC705 was evaluated from the technological point of view as a bioprotective culture in fermented foods and wheat bread applications. In this study, the role of<i>P. freudenreichii</i> ssp.<i> shermanii</i> JS as a candidate probiotic culture alone and in a combination with <i>L. rhamnosus</i> LC705 was demonstrated. Both strains were transiently recovered in high numbers in fecal samples of healthy adults during the consumption period. The good survival through the GI transit was proven for both strains with a recovery rate from 70 to 80% for the JS strain and from 40 to 60% for the LC705 strain from the daily dose of 10 log10 CFU. The good survival was shown from the consumption of fruit juices which do not provide similar matrix protection for the cells as milk based products. The strain JS did not pose