The hemicelluloses were isolated with 10% KOH at 25 degrees C from dewaxed and delignified bamboo powder. The alkali-soluble hemicelluloses from Sinocalamus affinis were fractionated by ammonium sulphate precipitation method. The bamboo alkali-soluble hemicelluloses yielded seven hemicellulosic fractions obtained at 0, 5, 15, 25, 40, 55, and 70% saturation with ammonium sulphate. It was found that the more branched hemicelluloses were precipitated at higher ammonium sulphate concentrations (55 and 70%), the more linear hemicelluloses were precipitated at lower ammonium sulphate concentrations (0, 5, 15, 25, and 40%). The molecular weights of hemicellulosic fractions become lower from 35,270 (Ho) to 18,680 (H-70) g mol(-1) with the increasing concentrations of saturated ammonium sulphate from 0 to 70%. Based on the FT-IR, H-1, C-13 and 2D HSQC NMR studies, the alkali-soluble hemicelluloses were 4-O-methyl-glucuronoarabinoxylans composed of the (1 -> 4)-linked beta-D-xylopyranosyl backbone with branches at O-3 of alpha-L-arabinofuranosyl or at O-2 of 4-O-methyl-alpha-D-glucuronic acid. (C) 2015 Elsevier Ltd. All rights reserved.