Description:
<jats:title>Summary</jats:title><jats:p>The preservation of the viability of microorganisms in probiotic formulations is the most important parameter ensuring the adequate concentration of live microorganisms at the time of administration. The formulation and processing techniques used to produce these probiotic formulations can influence the preservation of the microbial viability. However, it is also required that the bacteria maintain their key probiotic capacities during processing, formulation and shelf life. In this study, we investigated the impact of spray‐drying on different cell wall properties of the model probiotic strain <jats:italic>Lactobacillus rhamnosus </jats:italic><jats:styled-content style="fixed-case">GG</jats:styled-content>, including its adherence to intestinal epithelial cells. The <jats:italic>dltD</jats:italic> gene knock‐out mutant, <jats:italic>L. rhamnosus <jats:styled-content style="fixed-case">GG</jats:styled-content></jats:italic> <jats:styled-content style="fixed-case">CMPG</jats:styled-content>5540, displaying modified cell wall lipoteichoic acids, showed significantly increased colony‐forming units after spray‐drying and subsequent storage under standard conditions compared to wild‐type <jats:italic>L. rhamnosus </jats:italic><jats:styled-content style="fixed-case">GG</jats:styled-content>. In contrast, disruption of the biosynthesis of exopolysaccharides or pili expression did not impact survival. However, spray‐drying did significantly affect the adherence capacity of <jats:italic>L. rhamnosus </jats:italic><jats:styled-content style="fixed-case">GG</jats:styled-content>. Scanning electron microscopy confirmed that the pili, key surface factors for adherence to intestinal cells and mucus, were sheared off during the spray‐drying process. These data thus highlight that both the functionality and viability of probiotics should be assessed during the spray‐drying process and subsequent storage.</jats:p>