Enhancing the production of galacto-oligosaccharides by mutagenesis of Sulfolobus solfataricus β-galactosidase

► β-Galactosidase (LacS) from Sulfolobus solfataricus P2 was expressed in E. coli. ► Transglycosylation capability of LacS was enhanced by sited-directed mutagenesis. ► The mechanism of the enhancement of GOS production by mutants was explored.