Oligosaccharide production using ß-galactosidase from Lactobacillus bulgaricus and Kluyveromyces lactis in sweetened reconstituted nonfat dry milk

Authors: Guron, Giselle Kris; Hotchkiss, Arland; Bodnar, Brittany; Harron, Andrew; Renye Jr, John; McAnulty, Michael

Submitted to: Journal of Dairy Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/10/2025
Publication Date: N/A
Citation: N/A

Interpretive Summary: Health-conscious consumers are interested in probiotics and prebiotics in foods because of their potential positive impacts on their gut health. Dairy products, including yogurt, have been known as inexpensive and palatable sources of beneficial bacteria. This study shows that enzymes from food-grade microbes can produce long-chain carbohydrates, or oligosaccharides, from sweetened dairy ingredients that support the growth of health beneficial bacteria. These enzyme preparations have the potential to be applied to a wide variety of dairy ingredients, such as fermented foods or to upcycle sweetened dairy byproducts, to produce health beneficial prebiotics.

Technical Abstract: ß-galactosidase (B-gal) is a vital enzyme used in the food industry to reduce lactose from dairy ingredients through hydrolysis and to synthesize galacto-oligosaccharides (GOS), a known bifidogenic prebiotic, from galactose through transgalactosylation. To favor transgalactosylation, high carbohydrate concentrations must be available to accept the galactose. Many dairy products rely on sweeteners for flavor and texture, but it is not known if high non-lactose sugar concentrations in milk can also favor transgalactosylation. B-gal from GRAS status Lactobacillus bulgaricus strains B548, LB11, YB1, or Kluyveromyces lactis (KL) in the commercial product Lactozyme® 2600L were used to determine if the transgalactosylation activity is greater in reconstituted nonfat dry milk (NDM, 10%, wt/wt) with commercial sweeteners compared to the transgalactosylation activity that occurs in unsweetened NDM at 50 °C for 20 h. Sucrose (14.4%, wt/wt), corn syrup solids (14.4%, wt/wt), or a mixture of sucrose (9.9%, wt/wt) and corn syrup solids (4.5%, wt/wt) were dissolved with NDM (n=3), then heated with stirring for 30 minutes at 70 °C for batch pasteurization. For L. bulgaricus, whole cells were inoculated at 7 log CFU/mL, or the same quantity of cells were lysed prior to adding to the milk and carbohydrate mixtures, or 1.85 U of KL B-gal was used. The sucrose mixture released the highest glucose from all whole cell, lysate, and KL enzyme preps, with LB11 lysate releasing the highest (245.57 ± 25.16 mM). High-Performance Anion-Exchange Chromatography with Pulsed Amperometric Detection was used to visualize the presence of oligosaccharides with degrees of polymerization of 3 to 7. Oligosaccharides from YB1 lysate treated sucrose mixtures also increased the anaerobic growth of Bifidobacterium breve 2141 at 37 °C compared to untreated or KL B-gal treated sucrose mixtures. B-gal treatment of sucrose in nonfat milk with and without corn syrup can be a source of prebiotic oligosaccharides, although more work is needed to determine if background microbiota are involved in hydrolyzing sucrose, and if fructose is also polymerizing to form novel oligosaccharides.