The effect of xylanase treatment of rye bran on fermentation of dietary fibre and lignan conversion in vitro

Rye bran is rich both in fermentable dietary fibre and plant lignans. The fermentable dietary fibre components are arabinoxylan, beta-glucan and fructan [1], which produce short chain fatty acids and gases in bacterial fermentation in the human large intestine. Plant lignans (matairesinol, secoisolariciresinol, syringaresinol, pinoresinol and lariciresinol) are converted to mammalian lignans by bacterial fermentation, producing enterodiol and/or enterolactone [2]. The aim of the work presented here was to study the effect of processing of rye bran on the fermentation rate of carbohydrates and formation of enterodiol and enterolactone in vitro. Processed rye bran samples were prepared. Rye bran was extruded and treated with xylanase. Part of the xylanase treated rye bran was separated into water-extractable fraction and insoluble residue. All the samples were digested enzymatically prior to the fermentation with human faecal flora in vitro. Xylanase treatment of rye bran enhanced both fermentation rate of carbohydrates and formation of enterodiol. Water-extractable rye bran concentrate had the fastest fermentation rate and produced the highest amount of enterodiol, whereas the insoluble residue was the slowest producer of enterodiol. Slowly occurring enterolactone formation was not affected by the form of carbohydrate.
References 1 . Karppinen, S., Kiiliäinen, K., Liukkonen, K., Forssell, P. and Poutanen, K. 2001. Extraction and in vitro fermentation of rye bran fractions. J. Cereal Sci. 34: 269-278. 2. Heinonen, S., Nurmi, T., Liukkonen, K., Poutanen, K., Wähälä, K., Deyama, T., Nishibe, S. and Adlercreutz, H., 2001. In vitro metabolism of plant lignans: new precursors of mammalian lignans enterolactone and enterodiol. J. Agric. Food Chem. 49: 3178-3186.