Abstract Background Milk whey, a byproduct of the dairy industry has a negative environmental impact, can be used as a raw material for added-value compounds such as galactooligosaccharides (GOS) synthesis by β-galactosidases. Results B-gal42 from Pantoea anthophila strain isolated from tejuino belonging to the glycosyl hydrolase family GH42, was overexpressed in Escherichia coli and used for GOS synthesis from lactose or milk whey. Crude cell-free enzyme extracts exhibited high stability; they were employed for GOS synthesis reactions. In reactions with 400 g/L lactose, the maximum GOS yield was 40% (w/w) measured by HPAEC-PAD, corresponding to 86 % of conversion. This enzyme had a strong predilection to form GOS with β(1→6) and β(1→3) galactosyl linkages. Comparing GOS synthesis between milk whey and pure lactose, both of them at 300 g/L, these two substrates gave rise to a yield of 38% (60% of lactose conversion) with the same product profile determined by HPAEC-PAD. Conclusions B-gal42 can be used on whey (a cheap lactose source) to produce added value products such as galactooligosaccharides.

中文翻译：

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使用来自 Pantoea anthophila 的重组 β-半乳糖苷酶从乳糖和乳清合成 β(1→3) 和 β(1→6) 低聚半乳糖

摘要 背景乳清是乳制品工业的副产品，对环境有负面影响，可用作高附加值化合物的原料，例如通过 β-半乳糖苷酶合成低聚半乳糖 (GOS)。结果从属于糖基水解酶家族GH42的tejuino分离的Pantoea anthophila菌株的B-gal42在大肠杆菌中过表达并用于从乳糖或乳清合成GOS。粗制无细胞酶提取物表现出高稳定性；它们被用于GOS合成反应。在与 400 g/L 乳糖的反应中，通过 HPAEC-PAD 测量的最大 GOS 产率为 40% (w/w)，对应于 86% 的转化率。该酶强烈倾向于形成具有 β(1→6) 和 β(1→3) 半乳糖基键的 GOS。比较乳清和纯乳糖的 GOS 合成，两者均为 300 g/L，这两种底物产生了 38%（乳糖转化的 60%）的产率，具有由 HPAEC-PAD 确定的相同产物曲线。结论 B-gal42 可用于乳清（一种廉价的乳糖来源）以生产附加值产品，如低聚半乳糖。