Cloning and expression of β-galactosidase gene from Streptococcus thermophilus in Saccharomyces cerevisiae

The β-galactosidase gene ofStreptococcus thermophilus was cloned into plasmid vector, pVT100-U, and used to transform a strain ofEscherichia coli andSaccharomyces cerevisiae. Transformants which expressed β-galactosidase activity were obtained in bothE. coli andSaccharomyces cerevisiae, the highest activity found in a yeast recombinant. The expression and thermostability of the cloned β-galactosidase genes from different plasmid constructions were compared with the streptococcal β-galactosidase. The recombinant protein was equivalent to the specific activity and thermostability ofS. thermophilus.