Breeding of a Brewer's Yeast Possessing Anticontaminant Properties

Antibacterial and anti-wild yeast characters were introduced into a brewer's yeast to achieve a more positive microbial assurance in brewing. An antibacterial yeast that inhibits the growth of 11 beer-spoilage bacteria was screened from our stock cultures and mated with a killer yeast active against many brewery wild yeasts. After sporulation of the hybrid, a haploid clone (AGK27) possessing the two anticontaminant properties was obtained. This clone was protoplast-fused with our brewery yeast, and one fusant, MAK61, was selected out of many hybrid products. MAK61 had both anti-wild yeast and antibacterial characters, and the beer produced was considered acceptable, although the fermentation rate was a little slower than that of our current brewery yeast. This work demonstrates the practical breeding of a brewer's yeast using protoplast fusion to improve brewing characteristics.