A novel salt-tolerant GH42 β-galactosidase with transglycosylation activity from deep-sea metagenome

beta-Galactosidase is a widely adopted enzyme in the food and pharmaceutical industries. Metagenome techniques have the advantage of discovering novel functional genes, particularly potential genes from uncultivated microbes. In this study, a novel GH42 beta-galactosidase isolated from a deep-sea metagenome was overexpressed in Escherichia coli BL21 (DE3) and purified by affinity chromatography. The optimal temperatures and pH of the enzyme for o-nitrophenyl-beta-D-galactopyranoside (oNPG) and lactose were 40 degrees C, 6.5 and 50 degrees C, 7, respectively. The enzyme was stable at temperatures between 4 and 30 degrees C and within the pH range of 6-9. Moreover, it was highly tolerant to salt and inhibited by Zn2+ and Cu2+. The kinetic values of K-m and k(cat) of the enzyme against oNPG were 1.1 mM and 57.8 s(-1), respectively. Furthermore, it showed hydrolysis and transglycosylation activity to lactose and the extra monosaccharides could improve the productivity of oligosaccharides. Overall, this recombinant beta-galactosidase is a potential biocatalyst for the hydrolysis of milk lactose and synthesis of functional oligosaccharides.

Automated summary

In this study, a novel β-galactosidase was isolated from a deep-sea metagenome, overexpressed in Escherichia coli, and purified. The enzyme showed high activity at specific temperatures and pH conditions, and exhibited resistance to salt. Moreover, it displayed hydrolysis and transglycosylation activity towards substrates such as oNPG and lactose.