Mayer Jürgen, Conrad Jürgen, Klaiber Iris, Lutz-Wahl Sabine, Beifuss Uwe, Fischer Lutz
Department of Biotechnology, Institute of Food Technology, University of Hohenheim, Emil-Wolff-Strasse 14, 70599 Stuttgart, Germany.
J Agric Food Chem. 2004 Nov 17;52(23):6983-90. doi: 10.1021/jf048912y.
The enzymatic transgalactosylation from lactose to fructose leading to the prebiotic disaccharide lactulose was investigated using the beta-galactosidase from Aspergillus oryzae and the hyperthermostable beta-glycosidase from Pyrococcus furiosus (CelB). The conditions for highest lactulose yields relative to the initial lactose concentration were established on a 1 mL scale. Dependent on the initial molar ratio of lactose to fructose, more or fewer oligosaccharides other than lactulose were generated. Bioconversions on a 30 mL scale in a stirred glass reactor were performed, and lactulose yields of 46 mmol/L (44% relative to lactose) for CelB and 30 mmol/L (30% relative to lactose) for A. oryzae beta-galactosidase were achieved. Only <5% of other oligosaccharides were detectable. The corresponding productivities were 24 and 16 mmol/L/h, respectively. The molecular structure of lactulose was investigated in detail and confirmed after purification of the reaction solution by LC-MS and 1D and 2D NMR. Lactulose (4-O-beta-D-galactopyranosyl-D-fructose) was unambiguously proved to be the major transglycosylation disaccharide.
利用米曲霉β-半乳糖苷酶和激烈火球菌（Pyrococcus furiosus）的超嗜热β-糖苷酶（CelB），研究了乳糖到果糖的酶促转半乳糖基化反应，该反应生成益生元二糖乳果糖。在1 mL规模上确定了相对于初始乳糖浓度而言乳果糖产率最高的条件。根据乳糖与果糖的初始摩尔比，会生成或多或少除乳果糖之外的寡糖。在搅拌玻璃反应器中进行了30 mL规模的生物转化，CelB的乳果糖产率为46 mmol/L（相对于乳糖为44%），米曲霉β-半乳糖苷酶的乳果糖产率为30 mmol/L（相对于乳糖为30%）。仅可检测到<5%的其他寡糖。相应的生产率分别为24和16 mmol/L/h。通过LC-MS以及一维和二维NMR对反应溶液进行纯化后，详细研究并确认了乳果糖的分子结构。明确证明乳果糖（4-O-β-D-吡喃半乳糖基-D-果糖）是主要的转糖基化二糖。
