Lactulose

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Lactulose is a synthetic disaccharide which is composed of one molecule of galactose and one molecule of fructose linked by a β1→4 glycosidic bond (2). Because lactulose is not naturally occurring, lactose, which consists of glucose and galactose, is often used as the precursor molecule for lactulose production. In order to produce lactulose from lactose, isomerization of lactose must occur in which the galactose subunit is removed from lactose and joined to a molecule of fructose. Isomerization of lactose can be accomplished using chemical or enzymatic methods. Chemical methods employ an alkaline catalyst, such as sodium hydroxide or potassium hydroxide, in combination with a complexing agent, such as borate or aluminate, that will attach to lactulose and precipitate as an insoluble complex from the reaction system, thus shifting chemical equilibrium in favor of the formation of the lactulose product; lactulose synthesis by this method can result in up to 80% yield of lactulose. Enzymatic methods accomplish isomerization of lactose via transgalactosylation using β-galactosidases, which hydrolyze the β1→4 glycosidic bond of lactose. In the presence of fructose, the galactose subunit of lactose is ideally added to the hydroxyl group of the four prime carbon of fructose to form lactulose. However, the addition of galactose to fructose is not restricted to the four prime carbon because fructose contains other hydroxyl groups on multiple carbon atoms; therefore, enzymatic isomerization of lactose can yield various constitutional isomers of lactulose containing β1→1 or β1→6 glycosidic bonds (3).
The β1→4 glycosidic bond of lactulose is crucial to its function in humans and animals. The mucous membranes which line the upper in...

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...ely metabolized by beneficial bacteria in the colon, such as Bifobacteria and Lactobaccilli, which are essential to the maintenance of a healthy body (3).
Lactulose is safe for short-term and long-term use in every age from infants to the elderly (1, 2). Overconsumption of lactulose can cause too much water to diffuse into the bowels and results in diarrhea. However, this side effect can be remedied by administering a lower dosage of lactulose (1).

Works Cited

(1) Elkington, S.E. (1970). “Lactulose”. Gut 11 (1970): 1043-1048
(2) Panesar, P.S. and Kumari S. (2011). “Lactulose: production, purification, and potential applications”. Biotechonology Advances 29 (2011): 940-948
(3) Schuster-Wolff-Bühring, R., Fischer, L., and Hinrichs, J. (2010). “Production and physiological action of the disaccharide lactulose”. International Dairy Journal 20 (2010): 731-741

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