Structural Characterization Of Hemicelluloses And LCC Preparations Extracted From Neosinocalamus Affinis

Neosinocalamus affinis is a kind of common bamboo species. It has been widely cultivated in Sichuan Province with properties of strong adaptability, short life cycle, and other characteristics. The contents of cellulose, hemicelluloses, and lignin in Neosinocalamus affinis cell walls are similar to the wood species.In the present work, the physicochemical properties and structural features of the Neosinocalamus affinis bamboo hemicelluloses and lignin-carbohydrate complex (LCC) preparations were evaluated and characterized by high performance anion exchange chromatography (HPAEC), gel permeation chromatograph (GPC), Fourier transform infrared (FT-IR), and nuclear magnetic resonance (NMR). All the conclusions obtained were as follows:(1) Main chemical constituents of the raw material are ash, methylbenzene-ethanol extractives, carbohydrates, and lignin, which account for 81.4-99.2% relative to the oven dry raw material, and above 90% in mature bamboo. The ash, extractives, and acid-soluble lignin contents were higher in young bamboo culms. In addition, glucose and xylose are the main hydrolysis products of the carbohydrates, which are originated from cellulose and hemicelluloses. In mature Neosinocalamus affinis, the content of cellulose is roughly 45%, while the contents of hemicelluloses and lignin are approximately 20% and 23%, respectively. The hemicelluloses in the top region are higher than the other parts of the culms, and the bottom location contains the highest content of lignin.(2) Neutral solvent DMSO was adopted to effectively extract the bamboo hemicelluloses from different regions of the 1-3 years old bamboo culms, the yields of the nine parts of hemicellulose were between 6.5% and 9.8%. The Neosinocalamus affinis bamboo is composed of O-acetyl-arabino-4-O-methylglucurono-(1â†'4)-β-D-xylan with molecular weight about 40000 g/mol. The hemicelluloses from 1-2 years old bamboo culms were of small difference. However, the extracted hemicelluloses in 3-year-old bamboo culms had higher degree of branch while lower weight-average molecular weights and degree of acetylation, which were caused by a certain amount of starch analogues (glucoses linked by a-1,4 and 1,6 linkages).(3) The yields of young Neosinocalamus affinis bamboo LCC preparations were 2.1-3.9%. The LCC preparations contained typical G-S-H type lignin, and the content of acid-soluble lignin was higher than the acid-insoluble lignin. The S/G ratio varied in consistent with the proportion of the acid-soluble lignin. In other words, the mature bamboo culms contained higher content of S type lignin than the immature bamboo culms. The changes of β-5’ and phenyl glycoside linkages were identical with the value of S/G ratio, whereas the amounts of β-O-4’ and β-1’ presented a reductive tendency when the S/G ratio was increased. The relative amounts of β-β’, benzyl ether, and benzyl ester linkages were in line with the content of carbohydrates, which were increased firstly and then decreased with the development of the young bamboo culms.