The present invention relates to a discovery platform for screening one or more Streptococcus, Lactobacillus or Propionibacterium bacterial strains for the ability to produce and/or produce a high yield of galactooligosaccharides (GOS) comprising assessing the β-galactosidase activity of a strain under growth conditions and identifying whether the activity has: a) Miller Unit which are equal to or greater than about 60 for Streptococcus or Lactobacillus strains; or b) Miller Unit which are equal to or greater than about 3 for Propionibacterium strains. The present invention also relates to compositions incorporating GOS produced from bacterial strains identified by the screening process.
