Galactose fermentation and classification of thermophilic lactobacilli.

The ability to ferment galactose is a major characteristic which can be used to differentiate Lactobacillus helveticus (galactose positive) from Lactobacillus lactis and Lactobacillus bulgaricus (galactose negative). In milk cultures, galactose-positive strains produced d- and l-lactic acid with little galactose accumulation, whereas galactose-negative strains produced d-lactic acid, and galactose accumulated to high levels.