The Brewer’s Genomic Toolbox for Better Beer
Brewing beer is a complex process that requires careful control of its parameters, including the yeast strains used for fermentation. Brewer’s yeast (Saccharomyces cerevisiae) not only generates ethanol and carbon dioxide, but also creates flavors and aromas in beer. For example, ale yeast tends to produce fruity, spicy, or floral flavors and aromas, whereas lager yeast produces clean, crisp, and often subtle flavors. Here, we’ll examine how brewers have embraced genomic tools to survey yeast performance and improve the quality of their beer.
Genomic Tools to Study Yeast
The genetic makeup of a yeast strain greatly influences its metabolism and behavior in the fermentation tank. Scientists have used next generation sequencing (NGS) and PCR + Sanger sequencing to better understand the characteristics of yeast strains, such as alcohol tolerance, flocculation (the ability of yeast cells to clump together), and the production of specific flavors and aromas. These techniques are also used to fingerprint strains, enabling brewers to identify and monitor their yeast populations.
NGS and PCR + Sanger are powerful tools, each with strengths and limitations. Brewers may rely on both to accomplish multiple objectives. For example, NGS is the go-to approach when profiling the entire genome of a strain or deciphering the makeup of a highly heterogeneous population. In contrast, PCR + Sanger provides fast genotyping of isolated yeast colonies but can analyze only one locus at a time.
Yeast Strain Development
Brewers have also leveraged genetics to create and characterize hybrid yeast strains. By crossing different strains, they’ve bred new strains with desirable traits. Say a brewmaster wants to make a strong, lemony beer. She could hybridize a yeast strain known for its high alcohol tolerance with one capable of generating citrus flavors. Once a desirable strain is isolated, brewers can genotype it using sequencing. They can identify the specific genes and pathways responsible for these characteristics and find unique DNA sequences for fingerprinting.
Understanding the Brewing Environment
The fermentation tank houses a dynamic environment, as yeast transforms the wort into beer. Brewers use genomic approaches to take snapshots of the yeast population during this process and to track how it evolves over time — from batch to batch. With this information, brewers can select strains that perform well in their specific fermentation conditions. Those who rely on environmental yeast can characterize unknown strains to better understand their role in the brewing process.
Contamination from unintended yeast strains, bacteria, or allergens can significantly impact large-scale and microbrewing operations. From a swab of the fermentation tank, yeast and bacterial contaminants can be streaked on agar plates and submitted for genetic identification. DNA or RNA from certain allergens, such as hazelnuts, can be detected through ultra-sensitive methods such as NGS and quantitative PCR.
Genomic analysis has become an increasingly important tool in beer making, particularly for developing new strains of yeast and optimizing the brewing process. Methods based on NGS or PCR + Sanger sequencing can identify and characterize yeast strains with high sensitivity and specificity. Learn more about yeast colony sequencing and how it can speed up your research.