Abstract
BackgroundSoya and its derivatives represent nutritionally high quality food products whose major drawback is their high content of α-galacto-oligosaccharides. These are not digested in the small intestine due to the natural absence of tissular α-galactosidase in mammals. The passage of these carbohydrates to the large intestine makes them available for fermentation by gas-producing bacteria leading to intestinal flatulence. The aim of the work reported here was to assess the ability of α-galactosidase-producing lactobacilli to improve the digestibility of α-galacto-oligosaccharides in situ.ResultsGnotobiotic rats were orally fed with soy milk and placed in respiratory chambers designed to monitor fermentative gas excretion. The validity of the animal model was first checked using gnotobiotic rats monoassociated with a Clostridium butyricum hydrogen (H2)-producing strain. Ingestion of native soy milk by these rats caused significant H2 emission while ingestion of α-galacto-oligosaccharide-free soy milk did not, thus validating the experimental system. When native soy milk was fermented using the α-galactosidase-producing Lactobacillus fermentum CRL722 strain, the resulting product failed to induce H2 emission in rats thus validating the bacterial model. When L. fermentum CRL722 was coadministered with native soy milk, a significant reduction (50 %, P = 0.019) in H2 emission was observed, showing that α-galactosidase from L. fermentum CRL722 remained active in situ, in the gastrointestinal tract of rats monoassociated with C. butyricum. In human-microbiota associated rats, L. fermentum CRL722 also induced a significant reduction of H2 emission (70 %, P = 0.004).ConclusionThese results strongly suggest that L. fermentum α-galactosidase is able to partially alleviate α-galactosidase deficiency in rats. This offers interesting perspectives in various applications in which lactic acid bacteria could be used as a vector for delivery of digestive enzymes in man and animals.
Highlights
Soya and its derivatives represent nutritionally high quality food products whose major drawback is their high content of α-galacto-oligosaccharides
This system made use of respiratory chambers to monitor gas excretion in gnotobiotic rats in which the microbiota was first simplified to a single strain of C. butyricum that produces H2 from α-GOS fermentation (Cb rats)
Α-Gal-producing L. fermentum CRL722 is able to remove flatus-generating α-GOS both in soy milk and in the gastrointestinal tract of rats monoassociated with C. butyricum DSM10702 Prior to assessing the potential of L. fermentum CRL722 to allow the digestion of α-GOS in soy milk and in the rat gastrointestinal tract, the effect of the strain alone was assessed in a group of 4 Clostridium butyricum (Cb) rats taken from the group of 12 rats tested above (Cb-A rats, Figs. 2 and 5)
Summary
Soya and its derivatives represent nutritionally high quality food products whose major drawback is their high content of α-galacto-oligosaccharides These are not digested in the small intestine due to the natural absence of tissular α-galactosidase in mammals. Other key benefits of soya derive from its high content of isoflavones which are thought to exert a range of biological effects against hormone-dependent diseases such as breast and prostate cancer, menopausal symptoms, cardiovascular diseases, and osteoporosis [5] Taken together, these reported health benefits, along with growing consumer preference for plant-derived food rather than meat, have led to an increasing demand for soy products [6]. The resulting production of fermentative gases can induce abdominal pain as well as the social embarrassment associated with flatulence [7,8] Such negative aspects reduce the acceptability of soy products as a major human food source [9]
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