High-Throughput Screening of Industrial Brewing Yeast with Lower Synthetic Level of Acetaldehyde During Beer Production.

The high level of acetaldehyde produced by yeast is a significant concern for all enterprises of beer production. To obtain industrial beer yeast strains with low ability to produce acetaldehyde, a multi-step screening strategy was established, using Co60γ mutagenesis, high-throughput screening, and adaptive evolution. A mutant strain (Lager-C) with low production of acetaldehyde was obtained, which had 54% less activity of alcohol dehydrogenase and 64% more activity of acetaldehyde dehydrogenase. Consequently, the formation of acetaldehyde by the Lager-C strain was 63% lower than that of wild-type Lager yeast. In addition, the Lager-C strain maintained phenotypic stability and a consistently lower content of acetaldehyde when continuously fermented for five generations. Furthermore, this mutant strain has similar fermentation performance to that of the wild-type strain. Thus, this novel applied screening strategy and the Lager-C strain will lay a solid foundation for the subsequent development of improved yeast strains for the beer industry.