Steaming treatment of bamboo grass. II. Characterization of solubilized hemicellulose and enzymatic digestibility of water-extracted residue

Culms of bamboo grass were treated with saturated steam at temperatures of 169.7-206.2°. The effects of various factors in the steaming treatment on the composition of the solubilized sugars and on the enzymatic digestibility of the residual fiber were investigated. The factors included temperature, residence time, initial moisture content of the culms and extraction with water before steaming. Although the major factor in the steaming treatment was the temperature and residence time, the initial moisture content also much affected not only the overall yield of xylan derived sugars but also the digestibility of polysaccharides in the steamed fiber. Moisture content of 75% and more provided good recovery yields of xylo-oligosaccharides and improved the enzymatic digestibility of the steamed and water-extracted residue. Pre-extraction with water resulted in an increased rate of xylan autohydrolysis. No significant effect of the pre-extraction was, however, observed in the development of substrate accessibility to cellulase.