Nicole Buckley

Interactions of Lactic Acid Bacteria with Human Intestinal Epithelial Cells: Effects on Cytokine Production

As a participant in the mucosal immune response, the intestinal epithelial cell must respond to a variety of stimuli, including lactic acid bacteria (LAB) consumed in the diet. The objective of this study was to compare the abilities of several strains of LAB to modulate cytokine secretion by human intestinal epithelial cell (IEC) line HT-29. Certain strains of Lactobacillus rhamnosus, Lactobacillus delbrueckii, and Lactobacillus acidophilus suppressed the production of the chemokine RANTES by stimulated HT-29 IEC, although the magnitude of this suppression varied depending on the nature of the bacterial growth medium. Similarly, specific strains showed growth condition-dependent suppression of HT-29 interleukin-8 (IL-8) production. Strain-dependent effects were also seen for the suppression of tumor necrosis factor alpha (TNF-alpha) and transforming growth factor beta (TGF-beta) production. The binding of several of these bacterial strains to the HT-29 cell line was also examined. Different strains were found to have differing abilities to interact with IEC, with L. rhamnosus R0011 being the strain that generally had the most extensive effects on HT-29 cytokine production and also bound to HT-29 IEC most effectively. Modulation of IEC cytokine production has the potential to profoundly affect the mucosal microenvironment, influencing the immune response to pathogens and other ingested antigens.

Effect of fermentation by pure and mixed cultures of Streptococcus thermophilus and Lactobacillus helveticus on isoflavone and B-vitamin content of a fermented soy beverage

Enhancement of nutritional or vitamin content of foods is commonly touted as a major benefit of probiotics. In this paper, we examined the ability of three probiotic bacteria either alone or in combination to enhance nutritional content. Pure and mixed cultures of Streptococcus thermophilus ST5 and Lactobacillus helveticus R0052 or Bifidobacterium longum R0175 were used to prepare fermented soy beverages. The effects of strain, acidification and mixed cultures on the deconjugation of soy isoflavones were examined. Acidification to pH 4.7 alone resulted in a 7% drop in isoflavone levels. Deconjugation levels varied between the different glucosides. Fermentation by L. helveticus R0052 resulted in the 50% reduction in total glucosides with O-malonyl glucosides being reduced 64%. Fermentation by S. thermophilus ST5 or B. longum R0175 had no significant effect on isoflavone levels. Combining a S. thermophilus strain with a L. helveticus culture reduced the effectiveness of the latter. Fermentation did not significantly modify vitamin B1 or B6 levels.