Xylan Yield Research Articles

Effect of structural features on enzyme digestibility of corn stover

Corn stover was pretreated with excess calcium hydroxide (0.5 g Ca(OH) 2/g raw biomass) in non-oxidative and oxidative conditions at 25, 35, 45, and 55 °C. The enzymatic digestibility of lime-treated corn stover was affected by the change of structural features (acetylation, lignification, and crystallization) resulting from the treatment. Extensive delignification required oxidative treatment and additional consumption of lime (up to 0.17 g Ca(OH) 2/g biomass). Deacetylation reached a plateau within 1 week and there were no significant differences between non-oxidative and oxidative conditions at 55 °C; both conditions removed approximately 90% of the acetyl groups in 1 week at all temperatures studied. Delignification highly depended on temperature and the presence of oxygen. Lignin and hemicellulose were selectively removed (or solubilized), but cellulose was not affected by lime pretreatment in mild temperatures (25–55 °C), even though corn stover was contacted with alkali for a long time, 16 weeks. The degree of crystallinity slightly increased from 43% to 60% with delignification because amorphous components (lignin, hemicellulose) were removed. However, the increased crystallinity did not negatively affect the 3-d sugar yield of enzymatic hydrolysis. Oxidative lime pretreatment lowered the acetyl and lignin contents to obtain high digestibility, regardless of crystallinity. The non-linear models for 3-d hydrolysis yields of glucan ( Y g), xylan ( Y x), and holocellulose ( Y gx) were empirically established as a function of the residual lignin ( L) for the corn stover pretreated with lime and air.

Solubilization of Bamboo Grass Xylan by Steaming Treatment

Chopped culms of bamboo grass were treated with saturated steam over a range of temperatures and residence times. The effect of various parameters in the steaming treatment on the recovery yield and solubilization of xylan was investigated. The parameters included steaming temperature, residence time, initial moisture content of the substrate and solvent pre-extraction prior to steaming. Although the major factor in the steaming treatment was the temperature and residence time, solvent pre-extraction as well as initial moisture content of the substrate also significantly affected the solubilization of xylan. When the substrate was pre-extracted with water prior to steaming, a significant increase in the recovery yield of solubilized xylan was observed. The result is possibly explained by the removal of basic salts present in the original raw material