Utilization and acid production of beta-galactosyllactose by oral streptococci and human dental plaque

beta -Galactosyllactose is a trisaccharide containing the beta -galactosidi c linkage at the nonreducing end. The purpose of this study was to determin e whether certain oral streptococci could utilize four kinds of beta -galac tosyllactoses. Three of four beta- galactosyllactoses were unable to suppor t growth of the oral streptococci and to be a substrate for producing acid from the cell suspensions and dental plaque. 4'-beta -Galactosyllactose sup ported growth of Streptococcus sanguis ATCC 35105, ATCC 49298, Streptococcu s mitis ATCC 15914, Streptococcus oralis ATCC 35037, ATCC 10557 and Strepto coccus milleri 10707 and produced acid from dental plaque. Although beta -g alactosidase activities were observed in all the strains, 4'-beta -galactos yllactose could not be used as a carbon source for the growth of mutans str eptococci. Enzymes metabolizing 4'-beta -galactosyllactose were induced whe n S. oralis ATCC 10557 was cultured in medium containing galactose. These r esults suggested that 4'-beta -galactosyllactose could be as cariogenic as lactose if it is consumed frequently and retained for a long period in the mouth.