ASBC Methods of Analysis - Yeast-15: Differentiation of Ale and Lager Yeast Strains by Rapid X-α-GAL Analysis
ASBC Methods of Analysis
Differentiation of Ale and Lager Yeast Strains by Rapid X-α-GAL Analysis
The melibiose analog 5-bromo-4-chloro-3-indolyl-a-D-galactopyranoside (X-α-gal) has previously been used to differentiate lager strains (Saccharomyces pastorianus) from ale strains (S. cerevisiae). Differentiation of these two types of yeast is based on the capacity of lager strains to cleave the X-α-gal molecule through the action of melibiase. This results in the release of indol, which oxidatively polymerizes to give an insoluble blue-green dye. After incubation with X-α-gal solution, a lager yeast suspension produces a blue-green coloration while the color of an ale yeast suspension remains unchanged (cream or white). This method is a variation of a previous method with modifications to the format and reagent and yields results in ≥30 min.