Assessment of the effect of stress-tolerance acquisition on some basic characteristics of specific probiotics

• Derivative strains with increased heat-tolerance were obtained.
• The acquired tolerance influences how strains respond to the downstream processing.
• Freeze drying affected adhesion potential of the probiotic strains tested.
• The effect of freeze drying on adhesion appears to be strain dependent.
• Tolerance to processing stress can be improved via a heat-exposure step.

The production of viable functional probiotics presupposes stability of strain features in the final product. We evaluated the impact of acquisition of heat-tolerance and subsequent freeze-drying on the adhesion properties of Lactobacillus rhamnosus GG, Lactobacillus casei Shirota, Bifidobacterium lactis Bb-12 and Bifidobacterium animalis IF20/1 and on their ability to inhibit the adhesion of pathogens in a mucus model. Both fresh and freeze-dried cultures were evaluated. Significant differences were observed between fresh, freeze dried, fresh heat-tolerant and freeze dried heat-tolerant strains, especially in the ability of the freeze dried probiotics to exclude, displace or outcompete pathogens.Based on our study characterizing probiotic properties such as adhesion and competitive exclusion, it seems possible to adapt probiotics to processing stresses, such as heat, without significantly changing the probiotic properties of the strains assessed. This may provide new options for future probiotic production technology. However, our results also emphasize that the properties of the stress-adapted strains, as well as the effect of the production processes should always be assessed as these are strain-specific.