- 期刊
蔗渣半纖維之化學構造之研究
Studies on the Chemical Structure of Bagasse Hemicellulose
摘要
蔗渣經脫臘，脫木質素及脫果膠質等預先處理後，用5%氫氧化鉀溶液抽得含有木糖，樹膠醛糖及少量葡萄糖構成之粗半纖維，其木糖與樹膠醛糖的分子比爲5.5~5.6：1；用菲林試劑精製得一僅含木糖及樹膠醛糖的精製牛纖維，其分子比爲11.3~12.1：1，經電泳層次分析檢查，僅有一條移動帶，比旋光度爲-134°。用測定還原性末端基之化學法，測得蔗渣半纖維之平均重合度爲88，相當於克分子量11,634 g。精製蔗渣半纖維，以過碘酸鈉氧化，對每單位五碳糖基消耗0.93莫耳過碘酸鈉，產生0.032莫耳甲酸，但不生成甲醛。經Smith分解分析，得木糖及甘油等二種主要產物。精製蔗渣半纖維之部分加水分解，主要可檢出木糖之二醣體，並在反應初期，卽可檢出樹膠醛糖。精製蔗渣半纖維，施以完全甲基化後，其主要劃分溶於輕石油醚-氯仿(70：30，v/v)之混合液，完全加水分解可產生2,3,5-tri-O-methyl-L-arabinofuranose，2,3,4-tri-O-methyl-D-xylopyranose，2,3-di-O-methyl-D-xylopyranose及2-O-methyl-D-xylopyranosey，分子數比分別爲7.95：1.14：82.96：7.95，相當於五碳糖基數分別爲7、1、73及7個，因此推得精製蔗渣半纖維之構造，主要由木糖以β-1, 4結合構成主鎖，在某些C-3之位置上，有樹膠醛糖的分枝。
關鍵字
無資料並列摘要
After removal of wax, pectin and lignin, bagasse was extracted with 5% KOH solution to produce crude hemicellulose which contained D-xylose, L-arabinose and a trace of D-glucose. After purification of crude hemicellulose with Fehling's solution, it produced pure hemicellulose which contained D-xylose and L-arabinose. Their molar ratio was 11.3 ~ 12.2 ： 1. Electro-phoregram expressed only one moving band. Its specific rotation was -134°, and the degree of polymerization, determined by estimation of the reducing terminal end, was 88 units. When it reacted with periodate, it consumed 0.93 mole periodate and produced 32m mole formic acid per pentose unit. But it could not form formaldehyde. Smith degradation gave D-xylose and glycerol. Partial hydrolysis of pure bagasse hemicellulose gave xylobiose mainly. L-arabinose was detected in the beginning period of partial hydrolysis. The main fraction of completely methylated product of bagasse hemicellulose was soluble in the mixture of light petroleum ether-chloroform (70: 30, v/v). After complete hydrolysis, it produced 2,3,5-tri-O-methyl-L-arabinofuranose. 2,3,4-tri-O-methyl-D-xylopyranose, 2,3-di-O-methyl-D-xylopyranose and 2-O-methyl-D-xylopyranose with molar ratio of 7.95：1.14：82.96：7.95 which corresponds to 7, 1, 73 and 7 pentose units, respectively. Therefore, the bagasse hemicellalose was assigned a structure composed of D-xylose joined by β-1,4-glycosidic linkage with a single L-arabinofuranosyl branched residue at some C-3 positions of D-xylopyranosyl residues.