PMC

Scanning electron microscopy analysis of cell wall molecules on Lactobacillus rhamnosus GG before and after spray‐drying. SEM pictures showing the surface of the Lactobacillus rhamnosus GG wild‐type strain (WT) (ATCC53103) (A), the lipoteichoic acid mutant ΔdltD::Tc^R (CMPG5540) (B), the pili‐deficient ΔspaCBA::Tc^R mutant (CMPG5357) (C) and the EPS‐deficient ΔwelE::Tc^R mutant (CMPG5351) (D) before (1) and after (2) spray‐drying. The length and the number of pili (marked with an arrow) on each of the bacterium are visualized in the graphs under the SEM pictures.

Adhesion capacity of Lactobacillus rhamnosus GG before and after spray‐drying. Adhesion capacity of Lactobacillus rhamnosus GG wild‐type strain (WT) (ATCC53103), the pili‐deficient ΔspaCBA::Tc^R mutant (—pili) (CMPG5357) and the exopolysaccharide deficient ΔwelE::Tc^R mutant (∆EPS (++ pili) (CMPG5351) to Caco‐2 intestinal epithelial cells was evaluated after spray‐drying. The line on the ‘1’ mark represents the adhesion capacity of L. rhamnosus GG WT before spray‐drying, which was used as a reference. Values are shown as means ± standard error of the mean (two‐way ANOVA, Tukey's multiple comparisons test). GraphPad Prism, version 6.1 (GraphPad Software Inc, La Jolla, Ca, USA) performed the analytical test at a significance level α = 0.05 (indicated with asterisks). The experiment was repeated three times with three biological repetitions.

Evaluation of survival and viability of Lactobacillus rhamnosus GG after spray‐drying. A. The Lactobacillus rhamnosus GG wild‐type strain (WT) (ATCC53103), the lipoteichoic acid mutant ΔdltD::Tc^R (∆LTA) (CMPG 5540), the pili‐deficient ΔspaCBA::Tc^R mutant (represented as —pili in the graph) (CMPG5357) and the exopolysaccharide deficient ΔwelE::Tc^R mutant [∆EPS (++pili) (CMPG5351)] were routinely grown and spray‐dried (n = 4). The colony‐forming units before and after spray‐drying were compared, and the data are expressed as a logarithmic reduction of the colony‐forming units per gram powder after spray‐drying (∆log). B. The spray‐dried powders were stored at 4°C, and the viability was determined after 1, 4, 13 and 26 weeks (n = 3). After 26 weeks, the viability was below the detection limit (10³ CFU g⁻¹). Values are shown as means ± standard error of the mean. ANOVA test and Tukey's multiple comparisons test were used to determine differences in parametric data. GraphPad Prism, version 6.1 (GraphPad Software Inc) performed the analytical test at a significance level α = 0.05 (indicated with asterisks).