Blueberries as an additive to increase the survival of Lactobacillus johnsonii N6.2 to lyophilisation.

Effective cultivation methods, total cost, and biomass preservation are key factors that have a significant impact on the commercialisation and effectiveness of probiotics, such as Lactobacillus. Sugar polymers, milk and whey proteins have been suggested as good additives for industrial preparations. Alternative compounds, such as phytophenols, are a more attractive option, given their potential benefits to human health. The overall goal of this study was to determine if the addition of blueberry phytophenols improves the survival of Lactobacillus johnsonii N6.2 during the freeze-drying process. The addition of blueberry aqueous extract (BAE) stimulated the growth of L. johnsonii under aerobic conditions and improved the stationary phase survival of the bacteria. Furthermore, the addition of BAE to the culture media improved the endurance of L. johnsonii N6.2 to freeze-drying stress, as well as to storage at 4 °C for up to 21 weeks. Moreover, blueberry extract performed more effectively as a lyophilising additive compared to skim milk and microencapsulation with whey protein/sodium alginate. In sum, this study demonstrates that BAE is an effective additive to increase the growth and survival of L. johnsonii N6.2 when added to the culture medium and/or used as a lyophilising preservative. Moreover, BAE or other polyphenols sources might likely enhance growth and increase survival of more probiotic lactic acid bacterial strains.

Lactobacillus johnsonii N6.2 diminishes caspase-1 maturation in the gastrointestinal system of diabetes prone rats.

The cells of the gastrointestinal (GI) epithelium are the first to contact the microbiota and food components. As a direct consequence of this, these cells are the first line of defence and key players in priming the immune response. One of the first responses against GI insults is the formation of the inflammasome, a multiprotein complex assembled in response to environmental threats. The formation of the inflammasome regulates caspase-1 by cleaving it into its active form. Once activated, caspase-1 can cleave interleukin-1ß (IL-1ß), which promotes adaptive and humoral immunity. Some strains, like Lactobacillus johnsonii N6.2, are able to modulate the biosynthesis of important host metabolites mediating inflammation. Of these metabolites are the pro-inflammatory kynurenines. L. johnsonii N6.2 is able to downregulate kynurenines biosynthesis via a redox active mechanism negatively affecting indoleamine 2,3-dioxygenase activity. In this study, we evaluated the effects of L. johnsonii N6.2 combined with the natural antioxidant and anti-inflammatory molecule rosmarinic acid (RA). Inflammasome assembly and the kynurenine pathway were evaluated in GI samples of BioBreeding diabetes-prone (BB-DP) rats. In this work, BB-DP rats were fed daily with RA, L. johnsonii N6.2; or both combined. The transcriptional rate and proteins levels of inflammasome and kynurenine pathway components in ileum tissue were evaluated. Elevated levels of pro-caspase-1 were observed in rats fed with L. johnsonii, while RA had no effect on pro-caspase-1 expression. Western blot assays demonstrated that L. johnsonii fed rats showed lower levels of mature caspase-1, when compared to the other treatments. Furthermore, IL-1ß maturation followed a similar pattern across the treatments. Differences were also observed between treatments in expression levels of key enzymes in the kynurenine pathway. These findings support the role of L. johnsonii in modulating the assembly of the inflammasome as well as some steps of the pro-inflammatory kynurenine pathway.

A low-pH-inducible, stationary-phase acid tolerance response in Lactobacillus acidophilus CRL 639.

Acidity is an important environmental condition encountered by lactobacilli during food fermentation. In this report we show that triggering the stationary-phase acid tolerance response (ATR) in L. acidophilus CRL 639 depends on the final growth pH. In free-pH fermentation runs (final pH = 4.5), the cells were completely resistant to acid stress, whereas cells from cultures under controlled pH (pH = 6.0) were very sensitive. The relationship between the final pH and the development of cross-resistance to different kinds of environmental stress was also evaluated. The study of protein profiles showed the overexpression of 16 proteins from 6.5 to 70.9 kDa in stationary phase cells. Seven of these proteins (26.3, 41.4, 48.7, 49.3, 54.5, 56.1, and 70.9 kDa) were expressed as result of the stationary phase itself, while nine proteins (14.1, 18.6, 21.5, 26.9, 29.3, 41.9, 42.6, 49.6, and 56.2 kDa) were exclusively induced as a result of the drop in culture pH during free fermentation runs. These results strongly suggest the involvement of these proteins in cell adaptation to environmental changes.

Lactobacillus acidophilus autolysins inhibit Helicobacter pylori in vitro.

Antibacterial activity of 17 strains of lactobacilli was tested against 10 strains of H. pylori. The inhibition observed was related to the acid production and the low pH attained. No relationship between CagA phenotype of H. pylori strains and tolerance to lactic acid was observed. In mixed cultures, L. acidophilus CRL 639 showed an autolytic behavior after 24 h of culture. At this moment, H. pylori CCUG17874 showed a decrease of 2 log-cycle, and no viable count was detected after 48 h. The bactericidal effect of L. acidophilus CRL 639 in mixed cultures is related to a proteinaceous compound released after cell lysis.

Influence of bile on beta-galactosidase activity and cell viability of Lactobacillus reuteri when subjected to freeze-drying.

The effect of bile on beta-galactosidase activity and cell viability was investigated using two strains of Lactobacillus reuteri that were subjected to freeze-drying. In the presence of 0.15% oxgall, beta-galactosidase activity of the whole cells was significantly increased. After lyophilization, the cultures that had been treated with oxgall showed a low survival rate without changes in beta-galactosidase activity. The poor resistance of the cells to damage from freeze-drying might be related to the presence of membranous structures containing simple folds and buds of the cell membrane, as was observed by transmission electron microscopy.