Lignin is a constituent of plant cell walls and thus is classified as part of dietary fiber. However, little is known about the role of lignin in gastrointestinal fermentation. In these articles, soluble and insoluble lignin-rich fractions were prepared from Brewer's spent grain and subjected to an in vitro colon model to study its potential bioconversions and interactions with faecal microbiota.
No suppression of microbial conversion by the fractions was observed in the colon model, as measured as short-chain fatty acid production. Furthermore, no inhibition on the growth was observed when the soluble fraction was incubated with strains of lactobacilli and bifidobacteria. In fact, the soluble lignin-rich fraction enabled bifidobacteria to survive longer than with glucose. Several transiently appearing small phenolic compounds, structurally resembling units from lignin, were observed during the fermentation from both soluble and insoluble lignin fractions. This would indicate that the gut microbiota is able to release small monomers from lignin and metabolize these released compounds.
Niemi P, Aura A-M, Maukonen J, Smeds AI, Mattila I, Niemelä K, Tamminen T, Faulds CB, Buchert J, Poutanen K. Interactions of a Lignin-Rich Fraction from Brewer's Spent Grain with Gut Microbiota in Vitro. J. Agric. Food. Chem. 2013 DOI: 10.1021/jf401738x
Aura A-M, Niemi P, Mattila I, Niemelä K, Smeds A, Tamminen T, Faulds C, Buchert J, Poutanen K. Release of Small Phenolic Compounds from Brewer's Spent Grain and Its Lignin Fractions by Human Intestinal Microbiota in Vitro. J. Agric. Food. Chem. 2013 DOI: 10.1021/jf4024195
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