Comparative studies of hemicelluloses solubilized during the treatments ofmaize stems with peroxymonosulfuric acid, peroxyformic acid, peracetic acid, and hydrogen peroxide part 1. Yield and chemical characterization

Treatment of the water-extracted maize stems with peroxymonosulfuric acid a t 20 degrees C for 144 h, peroxyformic acid at 80 degrees C for 6 h, perace tic acid at 50 degrees C for 6 h, and 2 % hydrogen peroxide at 45 degrees C for 12 h at pH 1.5, 4.4, 9.5, 11.5, 12.0, and 12.6, respectively, solubili zed 47.1 %, 91.3 %, 33.3 %, 16.6%, 15.9 %, 17.4 %, 86.2 %, 87.7 %, and 91.3 % of the original lignin, and hydrolysed or dissolved 12.1 %, 99.1 %, 4.5 %, 2.7 %, 3.1 %, 3.1 %, 63.3 %, 64.7 %, and 83.0 % of the original hemicell uloses, respectively. Substantial lignins and hemicelluloses were degraded or released during the treatment with per oxyformic acid and alkaline perox ide at pH greater than or equal to 11.5, while an insignificant effect on d elignification and hemicellulose solubilization was observed by using perox ymonosulfuric acid, peracetic acid, and hydrogen peroxide in acidic, natura l, and weak alkaline media. The optimum condition for extraction of hemicel luloses was found to use 2 % H2O2 at 45 degrees C for 12 h at pH 11.5-12.0, which yielded 63.3-64.7 % of the original hemicelluloses having much light er color than those obtained by peroxymonosulfuric acid and peracetic acid under conditions used and 2 % H2O2 at pH 1.5, 4.4, 9.5, and 12.6. Xylose an d arabinose were the major sugar constituents in these hemicellulose prepar ations, whereas glucose, galactose, mannose, rhamnose, and fucose were pres ent as minor components. The alpha-ether linkages between lignin and hemice lluloses in the cell wall of maize stems were substantially cleaved during the treatment with 2 % H2O2 at pH greater than or equal to 11.5 as shown by a minimal amount of associated lignin (2.9-3.9 %), rich in syringyl units, in the solubilized hemicelluloses.