A Novel Thermal-Activated β-Galactosidase from Bacillus aryabhattai GEL-09 for Lactose Hydrolysis in Milk

beta-Galactosidase has been greatly used in the dairy industry. This study investigated a novel thermostable beta-galactosidase (lacZBa) from Bacillus aryabhattai GEL-09 and evaluated the hydrolytic performance of this enzyme. Firstly, the lacZBa-encoding gene was cloned and overexpressed in Escherichia coli BL21(DE3). Phylogenetic analyses revealed that lacZBa belonged to the glycoside hydrolase family 42. Using SDS-PAGE, we determined that the molecular weight of lacZBa was similar to 75 kDa. Purified lacZBa exhibited a maximum activity at 45 & DEG;C, pH 6.0, and could be activated following incubation at 45 & DEG;C for several minutes. The half-life of lacZBa at 45 & DEG;C and 50 & DEG;C was 264 h and 36 h, respectively. While Co2+, Mn2+, Zn2+, Fe2+, Mg2+, and Ca2+ enhanced enzymatic activity, Cu2+ and ethylenediaminetetraacetic acid inhibited enzymatic activity. Moreover, lacZBa could hydrolyze lactose and oNPG with K-m values of 85.09 and 14.38 mM. Molecular docking results revealed that lacZBa efficiently recognized and catalyzed lactose. Additionally, the hydrolysis of lactose by lacZBa was studied in lactose solution and commercial milk. Lactose was completely hydrolyzed within 4 h with 8 U/mL of lacZBa at 45 & DEG;C. These results suggested that lacZBa identified in this study has potential applications in the dairy industry.

Automated summary

In this study, a novel thermostable β-galactosidase (lacZBa) from Bacillus aryabhattai GEL-09 was investigated and found to have potential applications in the dairy industry. LacZBa exhibited maximum activity at 45°C and pH 6.0, and could hydrolyze lactose and oNPG. It efficiently recognized and catalyzed lactose, and could completely hydrolyze lactose in lactose solution and commercial milk within 4 hours at 45°C.