T. OTA (1), K. Kanai (1), H. Nishimura (1), S. Yoshida (1), T. Ichii (1), O. Kobayashi (1); (1) Kirin Company, Limited, Yokohama, Japan

Poster

Cross-breeding is an effective approach for the construction of novel yeast strains with improved traits. This method relies on the mating of spores, which is difficult for brewing yeast, especially the bottom-fermenting yeast known as Saccharomyces pastorianus. Bottom-fermenting yeast strains sporulate poorly, and only a fraction of the spores germinate, after which most have lost their ability to mate. For these reasons, mating-competent cells are barely available for bottom-fermenting yeast. By spontaneous mutation, however, stable mating-competent cells can be obtained from diploid brewing yeast or from spores of bottom-fermenting yeast, albeit at a very low frequency. This makes the isolation of mating-competent cells from brewing yeast difficult, laborious, and not very cost-effective. Here, we present a novel screening method for the isolation of mating-competent cells from brewing yeast. This method does not rely on genetic modification and allows for direct selection of mating-competent cells on plates, as will be discussed at the conference. Using this system we have been able to construct hybrids between different bottom-fermenting yeast strains. These hybrid strains carry traits of both parental strains, and because they have not been genetically engineered, they can be used for industrial brewing. To our knowledge, this is the first report of cross-breeding between different bottom-fermenting yeast strains. This novel method enables easy cross-breeding of brewing yeast strains, which will be advantageous for development of strains with novel breeding characteristics.

Taku Ota received a master’s degree in engineering from Osaka University, Japan, in 2010. He then began employment in the Central Laboratories for Frontier Technology with Kirin Holdings Company, Limited and has been engaged in the research and development of yeast and fermentation technology. Since January 2013, he has been working in the Research Laboratories for Brewing Technologies at Kirin Company, Limited.