Comparative study of alkali-soluble hemicelluloses isolated from bamboo (Bambusa rigida)

The physicochemical properties and structural characteristics of seven alkali-soluble hemicellulosic preparations were determined. These were extracted from bamboo (Bambusa rigida) with 1M NaOH, KOH, LiOH, NH(3)·H(2)O, (CH(3)CH(2))(3)N, Ca(OH)(2), Ba(OH)(2), respectively, at 50°C for 3h, were comparatively studied. Sugar analysis showed that these hemicelluloses contained d-xylose as the major constituent, along with d-glucose and l-arabinose in noticeable amounts. Uronic acids, principally 4-O-methyl-d-glucuronic acid, occurred in a small amount. Furthermore, based on the sugar analysis and FTIR and NMR spectroscopy, it can be concluded that the hemicelluloses consist of a backbone of β-(1→4)-linked d-xylopyranosyl units having branches of arabinose and 4-O-methyl-d-glucuronic acid. Nitrobenzene oxidation revealed that the hemicelluloses obtained are mostly free of bound lignins. Moreover, it is noteworthy that hemicelluloses isolated with the different alkaline solutions presented different chemical compositions and slightly dissimilar structural features, indicating that alkalinity played an important role in cleaving the chemical linkages between the hemicelluloses and the lignins.