Genetic improvement of brewer’s yeast: current state, perspectives and limits

Abstract

Brewer's yeast strain optimisation may lead to a more efficient beer production process, better final quality or healthier beer. However, brewer's yeast genetic improvement is very challenging, especially true when it comes to lager brewer's yeast (Saccharomyces pastorianus) which contributes to 90% of the total beer market. This yeast is a genetic hybrid and allopolyploid. While early studies applying traditional genetic approaches encountered many problems, the development of rational metabolic engineering strategies successfully introduced many desired properties into brewer's yeast. Recently, the first genome sequence of a lager brewer's strain became available. This has opened the door for applying advanced omics technologies and facilitating inverse metabolic engineering strategies. The latter approach takes advantage of natural diversity and aims at identifying and transferring the crucial genetic information for an interesting phenotype. In this way, strains can be optimised by introducing "natural" mutations. However, even when it comes to self-cloned strains, severe concerns about genetically modified organisms used in the food and beverage industry are still a major hurdle for any commercialisation. Therefore, research efforts will aim at developing new sophisticated screening methods for the isolation of natural mutants with the desired properties which are based on the knowledge of genotype-phenotype linkage.

Conventional and Non-Conventional Yeasts in Beer Production

“…This affects characteristics and ability of specific strains, whose genotype is influenced by strain origin. Strains with specific properties were correlated with some breweries or a locality, and genetic features, such as genomic arrangement, number of copies, ploidy, and polymorphisms characterize each strain [19]. Sequencing of the genomes of groups I and II lager yeasts confirmed these findings [20][21][22][23].…”

Lager Yeast Comes of Age

“…Other off flavors, such as dimethyl sulfide (DMS) and hydrogen sulfide (H 2 S), are derived from methionine metabolism (69). Yeasts can generate DMS from barley-derived dimethyl sulfoxide (DMSO).…”

“…Additionally, the use of genetically modified organisms (GMO) is viewed with great concern, and thus such strains are not commercialized. With recent advances in lager yeast genomics, new omics tools can be applied, and metabolic engineering and sophistication in high-throughput screening methodologies will advance the field in the future (69).…”

The Microbiology of Malting and Brewing

“…Saerens et al (152) and Nevoigt (153) have reviewed genetic strategies for improving brewing yeast. As regards the application of genetic modification (154), there is sensibly no such modified strain in commercial use globally (155).…”