Isolation and identification of the lactase (β-galactosidase) from the soil bacterium Weizmannia coagulans and its expression and production in the expression system of Escherichia coli

Lactase plays an important role in biotechnology and food industry, and the development of a lactase with high enzymatic activity and stability is the key to its industrial application. In this study, we isolated a lactase-producing strain from a dairy farm raw milk storage room. Whole genome sequencing analysis showed that the strain was Weizmannia coagulans, named Weizmannia coagulans LXL310-1, with a lactase activity of 0.817 U/mL. The lactase gene bgaB from W. coagulans was amplified by PCR and expressed in an Escherichia coli expression system. The enzyme was further purified following fermentation using ammonium sulfate precipitation, gel filtration and ion exchange chromatography. Lactase activity was enhanced 72.6 fold to 59.35 U/mL using this heterologous expression system. The lactase activity obtained in this study reached a high level. This study successfully established a systematic lactase recombinant expression system to provide a foundation for industrial lactase production and further theoretical investigations.