The enzyme β-galactosidase can synthesise novel prebiotics such as oligosaccharides derived from lactulose (OsLu) which can be added as a supplement in infant food formula. In this study, the intracellular β-galactosidase produced by the alkaliphilic bacterium Paracoccus marcusii was extracted and purified to homogeneity using hydrophobic and metal affinity chromatography. The purification resulted in 18 U/mg specific activity, with a yield of 8.86% and an 18-fold increase in purity. The purified enzyme was a monomer with an 86 kDa molecular weight as determined by SDS PAGE and Q-TOF-LC/MS. β-Galactosidase was highly active at 50 °C and pH 6–8. The enzyme displayed an alkali tolerant nature by maintaining more than 90% of its initial activity over a pH range of 5–9 after 3 h of incubation. Furthermore, the enzyme activity was enhanced by 37% in the presence of 5 M NaCl and 3 M KCl, indicating its halophilic nature. The effects of metal ions, solvents, and other chemicals on enzyme activity were also studied. The kinetic parameters K_M and V_max of β-galactosidase were 1 mM and 8.56 μmoles/ml/min and 72.72 mM and 11.81 μmoles/ml/min on using oNPG and lactose as substrates. P. marcusii β-galactosidase efficiently catalysed the transgalactosylation reaction and synthesised 57 g/L OsLu from 300 g/L lactulose at 40 °C. Thus, in this study we identified a new β-galactosidase from P. marcusii that can be used for the industrial production of prebiotic oligosaccharides.

β-半乳糖苷酶可以合成新型益生元，例如源自乳果糖的低聚糖 (OsLu)，可作为补充剂添加到婴儿食品配方中。在本研究中，嗜碱性细菌Paracoccus marcusii产生的细胞内 β-半乳糖苷酶使用疏水和金属亲和色谱法提取和纯化至均一。纯化导致比活性为 18 U/mg，产率为 8.86%，纯度提高 18 倍。经 SDS PAGE 和 Q-TOF-LC/MS 测定，纯化的酶是单体，分子量为 86 kDa。β-半乳糖苷酶在 50 °C 和 pH 6-8 时具有高活性。该酶在培养 3 小时后在 5-9 的 pH 范围内保持其初始活性的 90% 以上，从而显示出耐碱性质。此外，在 5 M NaCl 和 3 M KCl 存在下，酶活性提高了 37%，表明其具有嗜盐性。还研究了金属离子、溶剂和其他化学品对酶活性的影响。动力学参数 K _M和 V _maxβ半乳糖苷酶的分别为1 mM和8.56微摩尔/毫升/分钟和72.72 mM和使用11.81微摩尔/毫升/分钟ö NPG和乳糖作为底物。P. marcusii β-半乳糖苷酶有效催化转半乳糖基化反应，并在 40 °C 下从 300 g/L 乳果糖合成 57 g/L OsLu。因此，在本研究中，我们从P. marcusii中鉴定了一种新的 β-半乳糖苷酶，可用于益生元低聚糖的工业生产。