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Lactose is a natural disaccharide obtained from the milk of most mammals and a waste product of cheese and casein manufacturing. Over the past decades, lactose in whey has increasingly been promoted as an important resource, and an increasing number of significant advances have been made to investigate its healthy and functional properties. Lactose can be biotransformed into many kinds of derivatives, including galacto-oligosaccharides, epilactose, lactulose, lactosucrose, and D-tagatose. Biological efficiency and safety are critical for the enzymatic production of lactose derivatives from lactose. These lactose derivatives show a range of prominent physiological features and effects, such as prebiotic properties, indigestibility, and obesity prevention, which can be utilized in the pharmaceutical, health, and food industries. In this review, we present the properties and physiological effects of lactose derivatives, detailing their biological production by various enzymes and their applications in dairy products, especially directly in the milk industry.

Epilactose (4-O-β-d-galactopyranosyl-d-mannopyranose) is a rare disaccharide derived from lactose (4-O-β-d-galactopyranosyl-d-glucopyranose) and possesses prebiotic properties. Epilactose is needed for biological studies in high amounts and purified form. The purification of epilactose is challenging because it behaves similarly to lactose, the starting substance of the epilactose production process. Epilactose can be produced both chemically and enzymatically, using cellobiose 2-epimerases for the latter. In this study, a process for semi-preparative epilactose purification is presented. Firstly, epilactose was produced in a buffered system using recombinant cellobiose 2-epimerase from Flavobacterium johnsoniae. After the enzymatic conversion, some of the residual lactose was removed by crystallisation at 6 °C for 72 h. Subsequently, the lactose still remaining in the conversion mixture was separated from epilactose by ligand-exchange chromatography. The conditions for the most effective chromatographic separation of lactose and epilactose were determined using a design of experiments approach with surface response methodology. The best conditions led to an epilactose purity of 99 % with a total yield of 51 %.

Lactulose and epilactose are potentially prebiotic isomers of the milk sugar lactose. Enzymatically they can be produced using cellobiose 2-epimerases. These sugars are notoriously hard to quantify due to their chemical similarity, which results in incomplete separation. With a new commercial stationary phase we achieved baseline separation on a basic HPLC system. The method allows the parallel quantification of lactose, epilactose and lactulose within a wide range of concentrations befitting most food samples.

Epilactose (4-O-β-D-galactopyranosyl-D-mannose), an epimer of lactose, is a rare disaccharide existing extremely small quantities in heat-treated milk, in which epilactose is produced by non-enzymatic catalysis from lactose. This disaccharide is a kind of non-digestible carbohydrate, has a good prebiotic effect, and promotes intestinal mineral absorption. This article presents a review of recent studies on epilactose formation in food system, qualitative and quantitative analysis, and its physiological functions. In addition, the biochemical properties and kinetic parameters of the epilactose-producing enzyme, cellobiose 2-epimerase, are compared, and the biotechnological production of epilactose from lactose is reviewed.