Abstract: Production of low-lactose milk containing galactooligosaccharides was studied withβ-Galactosidase by transgalactosylation activity from Enterobacter sp.B5.In this way it can ease lactose intolerance.Meanwhile,the galactooligosaccharides as bifidus factor can promote the growth of bifidobacterium.The fresh cow milk was then directly treated withβ-galactosidase of transgalactosylation activity derived from Enterobacter sp.B5.The types and amounts of total sugars of processed milk were analyzed by thin layer chromatography(TLC),high pressure liquid chromatography(HPLC)and the software NIH ImageJ 1.36.About 70% of lactose contained in the cow milk was hydrolyzed to glucose and galactose,while at least 10% of lactose in the cow milk was changed into galactoofigosaccharides by the transgalactosidafion reaction.When the cow milk was treated withβ-galactosidase at an enzyme concentration of 3 U/ml at 50℃in 4 hours,a processed milk was obtained containing 0.59% of galactooligosaccharides including 0.37% of transgalactosylated disaccharides and 0.22% trisaccharide, 1.33% of lactose,and 2.83% of monosaccharide.The use of public-domain NIH ImageJ software for the quantitation of scanned images of thin-layer chromatography can help examine the transgalactosylated disaccharide(the isomer of lactose),which would otherwise not be detected in HPLC chromatogram comparatively.

Key words: &beta, -galactosidase； transgalactosidation； galactooligosaccharides； low-lactose milk；