Abstract
Isomerization of disaccharides (maltose, isomaltose, cellobiose, lactose, melibiose, palatinose, sucrose, and trehalose) was investigated in subcritical aqueous ethanol. A marked increase in the isomerization of aldo-disaccharides to keto-disaccharides was noted and their hydrolytic reactions were suppressed with increasing ethanol concentration. Under any study condition, the maximum yield of keto-disaccharides produced from aldo-disaccharides linked by β-glycosidic bond was higher than that produced from aldo-disaccharides linked by α-glycosidic bond. Palatinose, a keto-disaccharide, mainly underwent decomposition rather than isomerization in subcritical water and subcritical aqueous ethanol. No isomerization was noted for the non-reducing disaccharides trehalose and sucrose. The rate constant of maltose to maltulose isomerization almost doubled by changing solvent from subcritical water to 80 wt% aqueous ethanol at 220 °C. Increased maltose monohydrate concentration in feed decreased the conversion of maltose and the maximum yield of maltulose, but increased the productivity of maltulose. The maximum productivity of maltulose was ca. 41 g/(h kg-solution).
摘要:在亚临界水乙醇中研究了二糖(麦芽糖、异麦芽糖、赤霉糖、乳糖、甜菜碱、蔗糖和海藻糖)的异构化反应。注意到醛基二糖向酮基二糖的异构化明显增加,随着乙醇浓度的增加,它们的水解反应被抑制。在任何研究条件下,通过β-糖苷键连接的醛基二糖产生的酮基二糖的最大产量均高于通过α-糖苷键连接的醛基二糖产生的酮基二糖。在亚临界水和亚临界水乙醇中,酮基二糖甘露糖主要发生分解而非异构化。非还原性二糖海藻糖和蔗糖未观察到异构化。将溶剂从亚临界水改为80%乙醇水溶液后,麦芽糖向麦芽糖酮异构化的速率常数几乎翻倍,温度为220°C。在进料中增加麦芽糖单水合物浓度会降低麦芽糖的转化率和麦芽糖的最大产量,但会提高麦芽糖的生产率。麦芽糖的最大生产率约为41克/(小时·千克-溶液)。