Epsilon Open Archive

Abstract

Fermentation of foodstuffs has beneficial effects on shelf life, taste and texture and
possibly also health of the consumer. Products containing microbes with beneficial
health effects for the host are defined as probiotics. One probiotic bacterium,
Lactobacillus reuteri, has been shown to exert positive effects on a number of diseases
and disorders, including a possible protective role against increased intestinal
permeability or ‘leaky gut’. Increased intestinal permeability has been linked to e.g.
inflammatory bowel disease (IBD), irritable bowel disease (IBS), coeliac disease and
infectious diarrhoea. This study examined the effect of different cereal substrates on the
growth, general metabolism and production of potential bioactive compounds by L.
reuteri, with the aim of establishing a synbiotic formulation effective against increased
intestinal permeability. Combinations of six barley varieties and six strains of bacteria
were evaluated using standard plate counts, chemical analysis (1H-NMR) and a small
intestinal epithelial cell model (IPEC-J2). The overall growth of L. reuteri in barley
flour was good and reached higher densities in untreated compared with heat-treated
flours. Differences in growth were also seen between bacterial strains and barley
varieties. The general metabolism was similar for all strains with a few exceptions, e.g.
lower production of succinate from L. reuteri DSM 17938. Two potentially bioactive
compounds, γ-aminobutyric acid (GABA) and 3-hydroxypropionic acid (reuterin), were
detected in barley fermented by L. reuteri. GABA was present in unfermented flour at
similar levels as in the fermented counterpart, indicating no or low production by L.
reuteri. Reuterin production was detected as formation of 1,3-propanediol and was
strain-specific, being present in fermentation with DSM 17938 and ATCC PTA 6475.
Experiments with IPEC-J2 cells revealed an increase in epithelial permeability caused
by untreated flour, both fermented and unfermented. Treatment with heat-treated flour
had a slight increasing effect on permeability, but recovered over time. Pre-treatments
with live bacteria or fermented heat-treated flour before challenge with enterotoxigenic
E. coli revealed significantly lower leakage of a molecular probe (FITC-dextran, 4
kDa). However, neither live bacteria nor their metabolites had a protective effect on
epithelial permeability, measured as transepithelial electrical resistance (TEER).