Fermentation of barley flour with Lactobacillus reuteri

Fermentation of foodstuffs has beneficial effects on shelf life, taste and texture andpossibly also health of the consumer. Products containing microbes with beneficialhealth effects for the host are defined as probiotics. One probiotic bacterium,Lactobacillus reuteri, has been shown to exert positive effects on a number of diseasesand disorders, including a possible protective role against increased intestinalpermeability or ‘leaky gut’. Increased intestinal permeability has been linked to e.g.inflammatory bowel disease (IBD), irritable bowel disease (IBS), coeliac disease andinfectious diarrhoea. This study examined the effect of different cereal substrates on thegrowth, general metabolism and production of potential bioactive compounds by L.reuteri, with the aim of establishing a synbiotic formulation effective against increasedintestinal permeability. Combinations of six barley varieties and six strains of bacteriawere evaluated using standard plate counts, chemical analysis (1H-NMR) and a smallintestinal epithelial cell model (IPEC-J2). The overall growth of L. reuteri in barleyflour was good and reached higher densities in untreated compared with heat-treatedflours. Differences in growth were also seen between bacterial strains and barleyvarieties. 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 bioactivecompounds, γ-aminobutyric acid (GABA) and 3-hydroxypropionic acid (reuterin), weredetected in barley fermented by L. reuteri. GABA was present in unfermented flour atsimilar 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 wasstrain-specific, being present in fermentation with DSM 17938 and ATCC PTA 6475.Experiments with IPEC-J2 cells revealed an increase in epithelial permeability causedby untreated flour, both fermented and unfermented. Treatment with heat-treated flourhad a slight increasing effect on permeability, but recovered over time. Pre-treatmentswith live bacteria or fermented heat-treated flour before challenge with enterotoxigenicE. coli revealed significantly lower leakage of a molecular probe (FITC-dextran, 4kDa). However, neither live bacteria nor their metabolites had a protective effect onepithelial permeability, measured as transepithelial electrical resistance (TEER).