title: Galactooligosaccharides formation during enzymatic hydrolysis of lactose: towards a prebiotic-enriched milk.
abstract: The formation of galactooligosaccharides (GOS) in skim milk during treatment with several commercial β-galactosidases (Bacillus circulans, Kluyveromyces lactis and Aspergillus oryzae) was analysed in detail, at 4 and 40°C. The maximum GOS concentration was obtained at a lactose conversion of approximately 40-50% with B. circulans and A. oryzae β-galactosidases, and at 95% lactose depletion for K. lactis β-galactosidase. Using an enzyme dosage of 0.1% (v/v), the maximum GOS concentration with K. lactis β-galactosidase was achieved in 1 and 5h at 40 and 4 °C, respectively. With this enzyme, it was possible to obtain a treated milk with 7.0 g/L GOS - the human milk oligosaccharides (HMOs) concentration is between 5 and 15 g/L--and with a low content of residual lactose (2.1g/L, compared with 44-46 g/L in the initial milk sample). The major GOS synthesised by this enzyme were 6-galactobiose [Gal-β(1 → 6)-Gal], allolactose [Gal-β(1 → 6)-Glc] and 6'-O-β-galactosyl-lactose [Gal-β(1 → 6)-Gal-β(1 → 4)-Glc].
authors.affiliation: Instituto de Catálisis y Petroleoquímica, CSIC, 28049 Madrid, Spain.
authors.forename: Barbara
authors.initials: B
authors.lastname: Rodriguez-Colinas
authors.forename: Lucia
authors.initials: L
authors.lastname: Fernandez-Arrojo
authors.forename: Antonio O
authors.initials: AO
authors.lastname: Ballesteros
authors.forename: Francisco J
authors.initials: FJ
authors.lastname: Plou
mesh_terms: D000818:Animals; D002417:Cattle; D005690:Galactose / Q000737:chemistry*; D006801:Humans; D007716:Kluyveromyces / Q000201:enzymology; D007785:Lactose / Q000737:chemistry*; D008892:Milk / Q000737:chemistry* / Q000378:metabolism; D008895:Milk, Human / Q000737:chemistry; D009844:Oligosaccharides / Q000737:chemistry*; D056692:Prebiotics; D001616:beta-Galactosidase / Q000737:chemistry
chemical_list: D009844:Oligosaccharides; D056692:Prebiotics; D001616:beta-Galactosidase; D007785:Lactose; D005690:Galactose
keywords: Galacto-oligosaccharides; Human milk oligosaccharides; Lactose-free milk; Prebiotics; Transglycosylation; β-Galactosidase