Biodegradation of wheat straw lignocarbohydrate complexes (LCC)

Abstract

Hot water extractions of ground wheat straw were performed as part of a study to assess digestibility and utility as a substrate for ligninolytic fungi. The treatments gave solutions containing phenolics and carbohydrates. After 48 h reflux percolation or 3 h autoclaving, little additional carbohydrates or phenolics were extracted into the liquors. During percolation, the pH of the wet straw in the reflux thimble fell only slightly and it is difficult to attribute the extraction in this case to an autohydrolytic process catalyzed by organic acids liberated from the straw. Gel permeation chromatography enabled the separation of the extracts into fractions, several of which were free of reducing sugars but contained phenolics and bound carbohydrates. Rechromatography of these fractions failed to separate these two components, indicating a tight linkage between them. The bound sugars were identified as glucose, arabinose, xylose and traces of galactose, but uronic acids were absent. The high molecular size fraction was rich in glucose whereas lower molecular size fractions were richer in xylose and arabinose and poor in glucose.