Bioinformatics confirms that beer yeast has evolved along with the brewing technology from that of ancient to present times.
History of beer yeast
Yeast is one of those microorganisms that have been associated with human beings from the very beginning of their existence. They were domesticated for their ability to utilize sugars and easily convert them to alcohol and carbon dioxide giving food and beverages characteristic taste and odor. Archaeological evidence suggests that the use of yeasts in bakeries and breweries was well established as long back as to 2000 B.C. from the excavations made at Thebes dating back to the 11th Dynasty.
In 1680, Antonie van Leeuwenhoek was the first to describe the structure of yeast cells in beer, from a view through his hand-ground lenses. By the year 1876, Louis Pasteur established that fermentation was brought about by microorganisms. It was Joseph Lister who had developed the dilution technique to obtain pure cultures of microorganisms, employing this technique Emil Christian Hansen studied the morphology and physiology of yeasts over a span of 30 years and developed a comprehensive system of yeast taxonomy which was greatly expanded by many microbiologists like Guillermond, Kluyver, Lodder and many others.
Hansen worked in Old Carlsberg Brewery, Copenhagen and was investigating the cause of beer spoilage commonly referred to as “yeast turbidity”. Hansen isolated pure cultures of three different yeasts which were called Saccharomyces cerevisiae, S. ellipsoideus, and S. pastorianus. Through his works, S. cerevisiae was identified as the species that produces good quality beer. By 1883, Hansen had also designed equipment for the propagation of Brewer’s yeast on a large scale.
Evolutionary history of beer yeast
Yeast geneticist, Kevin Verstrepen from the University of Leuven and VIB in Belgium along with a team of bioinformaticians under the leadership of Steven Maere, a computational biologist at VIB and Ghent University, and a team of beer scientists from White Labs in California, sequenced the genomes of 157 different yeast strains. Yeasts are employed in the making of wine, bread, beer, sake, bioethanol and many more local and traditional foods. The analysis reveals that the ancestral lineage of the industrial yeast is limited to a few strains. Based on their industrial purpose the stains can be grouped into 5 large groups based on their genetic makeup.
The genomes of the strains are also characterized by their geographical location such that the strains from Belgium and Germany are more closely related to each other than their counterparts from UK and US. The genomic data helped the researchers unravel the ancestry of industrial beer and wild yeasts to far back into the 1500s when the world of microbes was unknown. This indicates that the ancient brewers were adept at their brewing technology although they lacked the knowledge of the existence of these secret agents of fermentation. The ancient brewers efficiently managed to harvest the yeast sediments from one batch to the next for fermentation. Reusing of the same organisms for fermentation totally separated them for the wild type and from nature itself such that the yeast evolved to adapt to the conditions of the brewery.
The study reveals that the brewer’s yeast is quite different from the wild type strains. The brewer’s yeast usually does not reproduce sexually, which is a characteristic trait of the wild type exhibited during starvation and stress. The brewer’s yeast has also developed traits that are desirable to the industry with the amplification, deletion, and modification of specific genes. The evolution has favored stress tolerance, flavor production, and sugar utilization.
Knowledge of evolution and adaptation will help the industry in the development of more resilient strains that will favor the production of best quality food and beverages. The team focuses on extending their research to breeding new industrial strains and also adding a brewery to their laboratory for further studies.