Advances in bio-production of lactulose using cellobiose 2-epimerases

Lactulose, a reducing disaccharide, is composed of D-galactosyl and D-fructosyl moieties via the ligation of a β-1,4 glycosidic bond. The concentrated lactulose solution can be used to treat chronic constipation and hepatic encephalopathy. It is an over-the-counter drug (OTC) worldwide, resulting in a massive requirement for its production. Lactulose is also a prebiotic that benefits human intestinal flora. Current industrial production of lactulose relies on chemical catalysis, with harmful catalyst and difficult in the down-stream processing. Recently, cellobiose 2-epimerase (CE) is recognized as an efficient biocatalyst for lactulose production using lactose as the substrate. This technique is environmentally friendly and composed of simpler procedures, showing promising future for an industrial application. This paper reviews recent developments in CE enzyme research, and the biotechnological route of lactulose synthesis.