Purification and characterisation of xylooligosaccharides (XOS) from wheat-based dried distillers grains with solubles

Abstract: The aim of this project was to purify xylan which is the major hemicellulose in wheat bran from dried distiller’s grains with solubles (DDGS). DDGS is a by-product from the fuel ethanol industry which uses wheat grain as a raw material. The wheat grain is used for the fermentation of starch to produce ethanol in the presence of yeast. The ethanol produced in this way is purified by distillation. The by-product DDGS is nowadays used as an animal feed. In this project we have investigated if it was possible to produce a value-added product from DDGS namely prebiotic xylooligosaccharides. The DDGS contains wheat bran rich in xylan and other hemicelluloses and compounds like starch, proteins, and fats. The DDGS was diluted in water and the extraction step was done to obtain the water-soluble xylans. The major impurity after the water extraction step is starch which is soluble in water. The hemicellulose fraction was purified from starch by using thermostable destarching enzymes, alpha-amylase and amyloglucosidase, followed by ethanol precipitation and dialysis. Xylan can be converted to xylooligosaccharides (XOS) by the treatment of xylan with xylanase. The obtained XOS have been analyzed with HPLC (High-performance liquid chromatography). The obtained xylooligo- saccharides have potential prebiotic properties. This prebiotic material can be used as a source of energy for bacteria called probiotic bacteria. Previous studies have shown many benefits of probiotic bacteria in human intestine for human health, which are widely used in a diary product such as yogurt. Small scale experiments were first performed to judge if enough purified xylan could be gained at the end of the purification procedures. In order to observe the prebiotic effect of this wheat based source, in vitro fermentation of probiotic bacteria was applied. The conclusion from the project was that xylooligosaccharides can be produced from DDGS. It was also indicated that probiotic bacteria can utilize XOS as carbon source.