Journal of the American College of Nutrition, Vol 5, Issue 3 281-290, Copyright © 1986 by American College of Nutrition

JOURNAL ARTICLE

The effect of the digestion products of lactose (glucose and galactose) on its intraintestinal, in vivo hydrolysis by exogenous microbial beta-D-galactosidase

J. L. Rosado, A. D. Deodhar, H. Bourges and N. W. Solomons

Exogenous, microbial beta-D-galactosidases are capable of effecting hydrolysis of lactose in situ in the gastrointestinal tract of lactase-deficient subjects when given as replacement therapy at mealtime. As its digestion products-glucose and galactose-are known to inhibit lactose hydrolysis in vitro, the effect of adding excess monosaccharide to milk on the hydrolytic efficiency of a beta-galactosidase from Aspergillus niger in adult lactose-malabsorbers was tested. Subjects were studied with 360-ml volumes of milk containing 18 g of carbohydrate. This was administered as intact milk, as lactose-prehydrolyzed milk, and as milk to which 399 mg of Lactase N was added within 5 minutes of consumption. This latter Lactase N-treated milk was administered alone and with graded levels of glucose-9, 18, and 36 g-and with similar doses of galactose. The Lactase N enzyme alone at mealtime reduced breath H2 production by 68% as compared to intact milk. The addition of monosaccharides produced no change in the apparent hydrolytic efficiency of the Lactase N in situ. Thus, product inhibition is unlikely to be the basis for the limited efficiency of intraintestinal hydrolysis of milk lactose by the enzyme from A niger.