ß-Galactosidase from Aspergillus oryzae offers a high yield for the synthesis of oligosaccharides derived from lactulose (OsLu) by transgalactosylation. Oligosaccharides with degree of polymerization (DP) ≥ 3 have shown to possess higher in vitro bifidogenic effect than di- and tetrasaccharides. Thus, in this work, an optimization of reaction conditions affecting the specific selectivity of A. oryzae ß-galactosidase for synthesis of OsLu has been carried out to enhance OsLu with DP ≥ 3 production. Assays with ß-galactosidase immobilized onto a glutaraldehyde-agarose support were also carried out with the aim of making the process cost-effective and industrially viable. Optimal conditions with both soluble and immobilized enzyme for the synthesis of OsLu with DP ≥ 3 were 50 °C, pH 6.5, 450 g/L of lactulose, and 8 U/mL of enzyme, reaching yields of ca. 50% (w/v) of total OsLu and ca. 20% (w/v) of OsLu with DP 3, being 6'-galactosyl-lactulose the major one, after a short reaction time. Selective formation of disaccharides, however, was favored at 60 °C, pH 4.5, 450 g/L of lactulose and 8 U/mL of enzyme. Immobilization increased the enzymatic stability to temperature changes and allowed to reuse the enzyme. We can conclude that the use, under determined optimal conditions, of the A. oryzae ß-galactosidase immobilized on a support of glutaraldehyde-agarose constitutes an efficient and cost-effective alternative to the use of soluble ß-galactosidases for the synthesis of\udprebiotic OsLu mixtures.
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机译:米曲霉的β-半乳糖苷酶通过反式半乳糖基化合成乳果糖(OsLu)衍生的寡糖具有很高的收率。聚合度(DP)≥3的寡糖已显示出比二糖和四糖更高的体外双歧化作用。因此,在这项工作中,已经进行了影响米曲霉β-半乳糖苷酶对OsLu合成的特异性选择性的反应条件的优化,以提高DP≥3的OsLu产量。还进行了将β-半乳糖苷酶固定在戊二醛-琼脂糖支持物上的测定,目的是使该方法具有成本效益并在工业上可行。 DP≥3的OsLu合成的可溶性和固定化酶的最佳条件是50°C,pH 6.5、450 g / L的乳果糖和8 U / mL的酶,达到大约产量。总OsLu的50%(w / v)和在较短的反应时间后,含有20%(w / v)的带有3的DP 3的OsLu,主要是6'-半乳糖基-乳果糖。然而,在60°C,pH 4.5,乳果糖450 g / L和8 U / mL酶的条件下,选择性形成二糖是有利的。固定化增加了酶对温度变化的稳定性,并允许重复使用该酶。我们可以得出结论,在确定的最佳条件下,固定在戊二醛-琼脂糖支持物上的米曲霉β-半乳糖苷酶的使用构成了使用可溶性β-半乳糖苷酶合成\ udprebiotic的一种有效且具有成本效益的替代方法OsLu混合物。
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