Extraction and characterization of lignins from maize stem and sugarcane bagasse

Lignins were isolated from maize stem and sugarcane bagasse by using mild dioxane or acidic dioxane solution. The result of nitrobenzene oxidation of the isolated lignins shows that there is a high proportion of p-hydroxyphenyl alcohol in the lignins of maize stem and sugarcane bagasse. The lignins isolated from maize stem and sugarcane bagasse have relatively same value of the weight-average ((M) over bar (w) = 3405-3868 g mol(-1)) and number-average ((M) over bar (n) = 1411-1612 g mol(-1)) molecular weights, and polydispersity ((M) over bar (w)/(M) over bar (n) 2.24-2.51). Acidic dioxane treatment did attack the beta-aryl ether structures in lignins, in particular for beta-aryl syringyl ethers, and broke the ester bonds between arabinose and ferulic acid that etherified to lignins, and it also cleaved lots of bonds in hemicellulosic polymer. The proportion of beta-O-4 (threo) guaiacyl units is higher than that of beta-O-4 (erthreo) guaiacyl units. The phenyl glycoside and benzyl ether linkages between lignin and hemicelluloses are also demonstrated in NMR analysis. (C) 2011 Wiley Periodicals, Inc. J Appl Polym Sci 120: 3587-3595, 2011