Epidemiological studies have clearly shown that whole-grain cereals can protect against obesity, diabetes, CVD and cancers. The specific effects of food structure (increased satiety, reduced transit time and glycaemic response), fibre (improved faecal bulking and satiety, viscosity and SCFA production, and/or reduced glycaemic response) and Mg (better glycaemic homeostasis through increased insulin secretion), together with the antioxidant and anti-carcinogenic properties of numerous bioactive compounds, especially those in the bran and germ (minerals, trace elements, vitamins, carotenoids, polyphenols and alkylresorcinols), are today well-recognised mechanisms in this protection. Recent findings, the exhaustive listing of bioactive compounds found in whole-grain wheat, their content in whole-grain, bran and germ fractions and their estimated bioavailability, have led to new hypotheses. The involvement of polyphenols in cell signalling and gene regulation, and of sulfur compounds, lignin and phytic acid should be considered in antioxidant protection. Whole-grain wheat is also a rich source of methyl donors and lipotropes (methionine, betaine, choline, inositol and folates) that may be involved in cardiovascular and/or hepatic protection, lipid metabolism and DNA methylation. Potential protective effects of bound phenolic acids within the colon, of the B-complex vitamins on the nervous system and mental health, of oligosaccharides as prebiotics, of compounds associated with skeleton health, and of other compounds such as alpha-linolenic acid, policosanol, melatonin, phytosterols and para-aminobenzoic acid also deserve to be studied in more depth. Finally, benefits of nutrigenomics to study complex physiological effects of the 'whole-grain package', and the most promising ways for improving the nutritional quality of cereal products are discussed.

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New hypotheses for the health-protective mechanisms of whole-grain cereals: what is beyond fibre?

Epidemiological studies associate whole grain consumption with a reduced risk of many diseases. This paper focuses on the antioxidant component of cereal dietary fibre starting from its chemical structure, bioavailability and biological meaning. By the critical assessment of the intervention studies performed using cereal bran and whole grains, the hypothesis that the slow and continuous release in the gut of the dietary fibre bound antioxidants determines the health benefits, is illustrated. In the last part of the work, new perspectives and technological possibilities to enhance the health potential of this cereal component are also highlighted.

Cereal dietary fibre: a natural functional ingredient to deliver phenolic compounds into the gut

Enzymatic and bacterial conversions during sourdough fermentation

This study aimed to identify phenolic acids and flavonoids in the red sorghum variety PAN 3860 and to determine changes in their concentrations during fermentation with lactobacilli. Sorghum sourdoughs fermented with two binary strain combinations, Lactobacillus plantarum and Lactobacillus casei or Lactobacillus fermentum and Lactobacillus reuteri , were compared to chemically acidified controls. Four glycerol esters were tentatively identified, caffeoylglycerol, dicaffeoylglycerol, coumaroyl-caffeoylglycerol, and coumaroyl-feruloylglycerol, that have previously not been detected in sorghum. Chemical acidification resulted in hydrolysis of phenolic acid esters and flavonoid glucosides. During lactic fermentation, phenolic acids, phenolic acid esters, and flavonoid glucosides were metabolized. Analysis of ferulic acid, caffeic acid, and naringenin-glucoside contents in single-strain cultures of lactobacilli demonstrated that glucosidase, phenolic acid reductase, and phenolic acid decarboxylase activities contributed to polyphenol metabolism. This study demonstrates that microbial fermentation of sorghum affects the content of polyphenols and can influence the nutritional value and antimicrobial activity of sorghum.

Phenolic Acids and Flavonoids in Nonfermented and Fermented Red Sorghum (Sorghum bicolor (L.) Moench)

Microbial production, characterization and applications of feruloyl esterases

Dietary ferulic acid (FA), a significant antioxidant substance, is currently the subject of extensive research. FA in cereals exists mainly as feruloylated sugar ester. To release FA from food matrices, it is necessary to cleave ester cross-linking by feruloyl esterase (FAE) (hydroxycinnamoyl esterase; EC 3.1.1.73). In the present study, the FAE from a human typical intestinal bacterium, Lactobacillus acidophilus, was isolated, purified, and characterized for the first time. The enzyme was purified in successive steps including hydrophobic interaction chromatography and anion-exchange chromatography. The purified FAE appeared as a single band in sodium dodecyl sulfate-polyacrylamide gel electrophoresis, with an apparent molecular mass of 36 kDa. It has optimum pH and temperature characteristics (5.6 and 37 degrees C, respectively). The metal ions Cu(2+) and Fe(3+) (at a concentration of 5 mmol liter(-1)) inhibited FAE activity by 97.25 and 94.80%, respectively. Under optimum pH and temperature with 5-O-feruloyl-L-arabinofuranose (FAA) as a substrate, the enzyme exhibited a K(m) of 0.0953 mmol liter(-1) and a V(max) of 86.27 mmol liter(-1) min(-1) mg(-1) of protein. Furthermore, the N-terminal amino acid sequence of the purified FAE was found to be A R V E K P R K V I L V G D G A V G S T. The FAE released FA from O-(5-O-feruloyl-alpha-L-arabinofuranosyl)-(1-->3)-O-beta-D-xylopyranosyl-(1-->4)-D-xylopyranose (FAXX) and FAA obtained from refined corn bran. Moreover, it released two times more FA from FAXX in the presence of added xylanase.

Purification and Characterization of a Feruloyl Esterase from the Intestinal Bacterium Lactobacillus acidophilus

In the present study, the production of a novel feruloyl esterase (FAE) from a typical human intestinal bacterium Lactobacillus acidophilus using various carbon sources was investigated. The results showed that FAE activity was strongly induced by hemicellulosic substances, with the highest activity detected when de-starched wheat bran (DSWB) was used as a carbon source. Moreover, the production was stimulated by the monosaccharides xylose and arabinose, suggesting its particular secretion mechanism. With increasing levels of free ferulic acid (FA) added, the production of FAE increased, reached a peak and declined. Further, on addition of either xylanase or α-L-arabinofuranosidase, the amount of FA released from DSWB by the purified FAE from L. acidophilus increased from 0 to 12.4nmol and 3.64nmol, respectively. When the three enzymes existed together, 15.7nmol of FA was detected. These results indicated that xylanase is predominant and arabinofuranosidase subordinate in their synergistic effect on FA release by FAE.

Release of Ferulic Acid from Wheat Bran by an Inducible Feruloyl Esterase from an Intestinal Bacterium Lactobacillus acidophilus

Effect of Different Molecular Weight Fragments from Corn Bran Hemicellulose on D-galactosamine-induced Hepatitis in Rats in Relation to Intestinal Degradation

Xiaokun Wang

Papers

Purification and Characterization of a Feruloyl Esterase from the Intestinal Bacterium Lactobacillus acidophilus

Release of Ferulic Acid from Wheat Bran by an Inducible Feruloyl Esterase from an Intestinal Bacterium Lactobacillus acidophilus

Effect of Different Molecular Weight Fragments from Corn Bran Hemicellulose on D-galactosamine-induced Hepatitis in Rats in Relation to Intestinal Degradation

Study on the Preventive Mechanism of Oligosaccharide Fragments from Corn Bran Hemicellulose against D-galactosamine-induced Hepatitis in Rats