Molecular Analyses of Yeast DNA—Tools for Pure Yeast Maintenance in the Brewery¹

Abstract

Modern molecular genetic techniques, commonly designated as “DNA fingerprinting techniques,” can now be used to identify any brewer's or wild yeast. By molecular and genetic analyses, it has been established that Saccharomyces carlsbergensis brewer's yeasts contain a unique combination of chromosomes. 5. carlsbergensis lager yeasts all originate from an ancestral species hybrid. The ancestors to 5. carlsbergensis seem to be a 5. cerevisiae top-fermenting yeast and a S. monacensis lager yeast. This unique combination of the S. carlsbergensis genetic material allows for unambiguous identification of the industrially used 5. carlsbergensis strains, because Saccharomyces yeasts of any other genetic background, either industrial strains or wild yeasts, are different from the lager yeast. Twenty-one brewer's yeast isolates and eight genetic reference strains were analyzed. The genetic studies were performed by analyses of the electrophoretic karyotypes and subsequent identification of chromosomes XII (RDN1) and V (URA3 and ILV1), as well by analyses of the restriction fragment length polymorphism patterns of URA3 located on chromosome V. The article shows that large-scale chromosomal size polymorphisms and differences in copy number of the chromosomes are present in 5. carlsbergensis brewer's yeasts at chromosomes XII and V.