Production of keto-disaccharides from aldo-disaccharides in subcritical aqueous ethanol

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).

Promoted isomerization of aldoses to ketoses in subcritical aqueous acetonitrile

“…The aldo‐disaccharides, cellobiose, maltose, lactose, and melibiose, mainly isomerized to their respective corresponding keto‐disaccharides, cellobiulose, maltulose, lactulose, and melibiulose, in high yields with a small amount of monosaccharides produced from the hydrolysis of disaccharides and the mutual isomerizations. In addition, the hydrolysis of the aldo‐disaccharides was suppressed compared to the case in subcritical water . In particular, cellobiulose and maltulose can be produced in ∼ 65 % and 51 % yields, respectively, with high selectivities and total disaccharide contents in the effluent.…”

“…These results also showed the effects of the type of glycosidic bond and constituent monosaccharides of the aldo‐disaccharides on their isomerizations. The aldo‐disaccharides linked by β ‐glycosidic bonds (cellobiose and lactose) produced the corresponding keto‐disaccharides in higher yields and selectivities than those linked by α ‐glycosidic bonds (maltose and melibiose), which was similar to the case in subcritical aqueous ethanol . However, the effect of the constituent monosaccharides on the aldo‐saccharide isomerization was not detected in subcritical aqueous ethanol.…”

“…Maltulose, lactulose, d ‐mannose, and acetonitrile were purchased from Nacalai Tesque (Japan). Melibiulose and cellobiulose for calibration were synthesized using our reported method . The prefix, d ‐, of all saccharides was omitted, since the present study focused on the isomerization of only the d ‐enantiomers.…”

Interconversion Between D-glucuronic Acid and D-glucuronolactone in Subcritical Aqueous Ethanol

“…GlcA is converted to d-glucuronolactone (GlcL) in subcritical water (Wang et al, 2010). We previously reported that the addition of ethanol to water significantly promotes the isomerization of mono-and disaccharides under subcritical conditions (Gao et al, 2014;2015a;2015b;2015c;2016).…”

Kinetics of the Disappearance of <i>N</i>-Acetyl-D-glucosamine in Subcritical Aqueous Ethanol

“…Under subcritical conditions, a mixture of ethanol and water was more effective than water alone for the extraction of phenolic and antioxidative substances from defatted rice bran and rice straw [17,18]. The isomerization of common saccharides to rare ones was promoted by the addition of ethanol to water [19,20]. Although the treatment of chitin in subcritical aqueous ethanol was not examined, similar treatment of GlcNAc and glucosamine should provide basic knowledge on the phenomena that occur during the treatment.…”