Microbiology Session
Weina Xu, Jiangnan University, Wuxi, Jiangsu Province, China
ABSTRACT: Yeast is the soul of beer fermentation. During
fermentation, yeast produces numerous beer flavor compounds, including
esters, acetaldehyde, and higher alcohols. At the same time, some other
characteristics of brewer’s yeast, such as cell age, fermentation rate,
and flocculation, are also important in the brewing industry. Brewer’s
yeast has a decisive influence on beer fermentation. Most industrial
brewer’s yeasts are lager yeasts and are generally natural genetic
hybrids, heterothallic polyploidies, or aneuploidies. Their intricate
ploidies present a great challenge to genetic studies and strain
improvement. Haploid breeding is an effective method to overcome these
difficulties. In this study, we established a systematic method to
induce, separate, and identify haploid strains of industrial brewer’s
yeast. Firstly, efficient sporulation medium was selected to induce
sporulation of industrial brewer’s yeast strain G-03. Then spores were
isolated from vegetative cells and formed colonies on YPD plates. Flow
cytometry was employed to determine the ploidy types of the pre-judged
haploid candidates. The genotypes were analyzed by PCR for the MAT locus
and mating test. Using this protocol, 26 yeast strains were obtained by
spore isolation. Four that were pre-judged as haploid candidates were
finally confirmed as haploid by flow cytometric analysis, two of them
were MATa, and others were MATalpha. This protocol proved practical for
breeding haploid strains of other industrial brewer’s yeasts as well
.
W
eina
Xu received a B.E. degree in bioengineering from Dalian University and
is currently a doctoral student in fermentation engineering at Jiangnan
University. She has studied microbiology for several years, and now is
devoting herself to the breeding and improving of brewer’s yeasts.
VIEW PRESENTATION 173