Batch and continuous synthesis of lactulose from whey lactose by immobilized β-galactosidase

► Lactulose synthesized from whey lactose in batch and continuous systems. ► The optimal concentration of fructose for lactulose synthesis was 20% (w/v). ► Sugars inhibited the transgalactosylation reaction more strongly than hydrolysis. ► Inhibition constants increased markedly by immobilization of enzyme. ► Lactulose synthesis in a continuous system was higher than that in a batch system.