Development of bottom-fermenting saccharomyces strains that produce high SO2 levels, using integrated metabolome and transcriptome analysis.
Sulfite plays an important role in beer flavor stability. Although breeding of bottom-fermenting Saccharomyces strains that produce high levels of SO(2) is desirable, it is complicated by the fact that undesirable H(2)S is produced as an intermediate in the same pathway. Here, we report the development of a high-level SO(2)-producing bottom-fermenting yeast strain by integrated metabolome and transcriptome analysis. This analysis revealed that O-acetylhomoserine (OAH) is the rate-limiting factor for the production of SO(2) and H(2)S. Appropriate genetic modifications were then introduced into a prototype strain to increase metabolic fluxes from aspartate to OAH and from sulfate to SO(2), resulting in high SO(2) and low H(2)S production. Spontaneous mutants of an industrial strain that were resistant to both methionine and threonine analogs were then analyzed for similar metabolic fluxes. One promising mutant produced much higher levels of SO(2) than the parent but produced parental levels of H(2)S.
Yoshida
Satoshi
S
Central Laboratories for Frontier Technology, KIRIN Holdings Co., Ltd., 1-13-5 Fukuura Kanazawa-ku, Yokohama-shi, Kanagawa 236-0004, Japan. satoshiy@kirin.co.jp
Imoto
Jun
J
Minato
Toshiko
T
Oouchi
Rie
R
Sugihara
Mao
M
Imai
Takeo
T
Ishiguro
Tatsuji
T
Mizutani
Satoru
S
Tomita
Masaru
M
Soga
Tomoyoshi
T
Yoshimoto
Hiroyuki
H
D001224:Aspartic Acid / Q000378:metabolism; D004798:Enzymes / Q000235:genetics / Q000378:metabolism; D005285:Fermentation; D005516:Food Microbiology; D017353:Gene Deletion; D018628:Gene Dosage; D020869:Gene Expression Profiling; D006714:Homoserine / Q000378:metabolism; D006862:Hydrogen Sulfide / Q000378:metabolism; D053858:Metabolic Networks and Pathways / Q000235:genetics; D016254:Mutagenesis, Insertional; D009154:Mutation; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism; D013431:Sulfates / Q000378:metabolism; D013458:Sulfur Dioxide / Q000378:metabolism*
D004798:Enzymes; D029701:Saccharomyces cerevisiae Proteins; D013431:Sulfates; D013458:Sulfur Dioxide; D001224:Aspartic Acid; D006714:Homoserine; D006862:Hydrogen Sulfide