Galactooligosaccharides (GOS) are synthesized by the enzyme β‐galactosidase during the hydrolysis of lactose. In this so‐called transgalactosylation reaction the galactosyl moiety is transferred to another sugar molecule instead of water resulting in oligosaccharides of different chain lengths and glycosidic linkages. Because their structures are similar to oligosaccharides present in human breast milk, they act as prebiotics, which has been shown for infants and adults to be alike. While so far most of the research to maximize GOS yield has been carried out using buffered lactose solution as a starting material, more and more work is now conducted with dairy by‐products such as whey and whey permeate, or even milk, for direct GOS synthesis in order to develop new GOS‐enriched dairy products. This review aims to summarize the results obtained with various dairy liquids, and it rates their suitabilities to act as raw material for GOS production. Most of the studies using whey or milk have been carried out with enzymes from Aspergillus oryzae, Kluyveromyces lactis, Bacillus circulans, Streptococcus thermophilus, and several Lactobacillus species. As the initial lactose concentration (ILC) is known to be a crucial factor for high GOS yield, most of the research has been done with concentrated or supplemented milk and whey. However, a clear dependency on ILC could only be observed for the A. oryzae lactase, indicating a strong influence of milk components like minerals and proteins on the transfer activities of most enzymes.

中文翻译：

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牛奶和乳清中低聚半乳糖的合成研究进展

低聚半乳糖（GOS）是由乳糖水解过程中的β-半乳糖苷酶合成的。在这种所谓的转半乳糖基化反应中，半乳糖基部分被转移到另一个糖分子而不是水上，从而产生具有不同链长和糖苷键的寡糖。由于它们的结构与人母乳中存在的低聚糖相似，因此它们起着益生元的作用，已被证明对婴儿和成人具有相同的作用。到目前为止，大多数研究都是通过使用缓冲乳糖溶液作为起始原料来实现的，从而使GOS的产量最大化，但是现在越来越多的研究工作涉及乳清副产品，例如乳清和乳清渗透液，甚至牛奶，用于直接GOS。合成以开发新的富含GOS的乳制品。这篇综述旨在总结使用各种乳制液体获得的结果，并对它们用作GOS生产原料的适用性进行评估。大多数使用乳清或牛奶的研究都是使用来自米曲霉，乳酸克鲁维酵母，圆形芽孢杆菌，嗜热链球菌和几种乳酸菌。由于已知初始乳糖浓度（ILC）是高GOS产量的关键因素，因此大多数研究都是通过浓缩或补充牛奶和乳清进行的。但是，只有米曲霉乳糖酶才能观察到对ILC的明显依赖性，这表明牛奶成分（如矿物质和蛋白质）对大多数酶的转移活性具有强烈的影响。