title: 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).
authors.affiliation: a Division of Food Science and Biotechnology , Graduate School of Agriculture, Kyoto University , Kyoto , Japan.
authors.forename: Da-Ming
authors.initials: DM
authors.lastname: Gao
authors.affiliation: a Division of Food Science and Biotechnology , Graduate School of Agriculture, Kyoto University , Kyoto , Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Kobayashi
authors.affiliation: a Division of Food Science and Biotechnology , Graduate School of Agriculture, Kyoto University , Kyoto , Japan.
authors.forename: Shuji
authors.initials: S
authors.lastname: Adachi
mesh_terms: D002475:Cellobiose / Q000737:chemistry; D004187:Disaccharides / Q000737:chemistry*; D000431:Ethanol / Q000737:chemistry*; D006868:Hydrolysis; D007534:Isomaltose / Q000031:analogs & derivatives / Q000737:chemistry; D007700:Kinetics; D007785:Lactose / Q000737:chemistry; D009682:Magnetic Resonance Spectroscopy; D008320:Maltose / Q000737:chemistry; D008553:Melibiose / Q000737:chemistry; D012996:Solutions; D013237:Stereoisomerism; D013395:Sucrose / Q000737:chemistry; D014199:Trehalose / Q000737:chemistry; D014867:Water / Q000737:chemistry*
chemical_list: D004187:Disaccharides; D012996:Solutions; D014867:Water; D002475:Cellobiose; D000431:Ethanol; D013395:Sucrose; D007534:Isomaltose; D008320:Maltose; D008553:Melibiose; D014199:Trehalose; D007785:Lactose; C008189:isomaltulose
keywords: isomerization; keto-disaccharide; subcritical aqueous ethanol; type of glycoside linkage