Structural characterization of hemicellulosic polysaccharides isolated from bamboo (Phyllostachys pubescens Mazel)

In the present work water soluble hemicellulosic polysaccharides HPW, 2% NaOH soluble hemicelluloses HPI and HPIII, and 5% KOH soluble fractions HPII and HPIV, were classically separated from bamboo (Phyllostachys pubescens Mazel) aged one year. In addition to sugar composition analysis, the hemicelluloses were also elucidated by GPC, FTIR, NMR and AFM techniques. Xylose (33.70-74.09%) and arabinose (25.03-59.04%) were the main neutral sugar, with ratios of arabinose to xylose being between 0.34 and 1.70. GPC measurement showed that the fractions HPW, HPII and HPIII precipitated in ethanol presented much broader molecular weight distribution. FTIR and NMR analysis suggested that the bamboo hemicelluloses could be mainly defined as arabinoxylans substituted by (1→2)-linked 4-O-methyl-α-D-glucuronic aid and acetyl group as side chains. AFM images of HPIII revealed a distribution of both island and rod aggregations when 0.01 mg/mL sample in 0.1 M NH ₄Ac solution was deposited onto freshly cleared mica and air dried.