β-Galactosidase-immobilised microreactor fabricated using a novel technique for enzyme immobilisation and its application for continuous synthesis of lactulose

► Functionalised multi-walled carbon nanotubes (MWNTs) used for β-galactosidase immobilisation. ► Pretreatment of β-galactosidase with lactose before immobilisation. ► Functionalised MWNTs increased the amount and activity of immobilised enzymes. ► A simple pretreatment step improved the activity of the immobilised enzyme. ► Findings will be useful for enzyme conversion in a continuous flow system.