title: Prevention of GABA reduction during dough fermentation using a baker's yeast dal81 mutant.
abstract: γ-Aminobutyric acid (GABA) is consumed by yeasts during fermentation. To prevent GABA reduction in bread dough, a baker's yeast mutant AY77 deficient in GABA assimilation was characterized and utilized for wheat dough fermentation. An amber mutation in the DAL81 gene, which codes for a positive regulator of multiple nitrogen degradation pathways, was found in the AY77 strain. The qPCR analyses of genes involved in nitrogen utilization showed that transcriptional levels of the UGA1 and DUR3 genes encoding GABA transaminase and urea transporter, respectively, are severely decreased in the AY77 cells. The AY77 strain cultivated by fed-batch culture using cane molasses exhibited inferior gas production during dough fermentation compared to that of wild-type strain AY13. However, when fed with molasses containing 0.5% ammonium sulfate, the mutant strain exhibited gas production comparable to that of the AY13 strain. In contrast to the AY13 strain, which completely consumed GABA in dough within 5 h, the AY77 strain consumed no GABA under either culture condition. Dough fermentation with the dal81 mutant strain should be useful for suppression of GABA reduction in breads.
authors.affiliation: NARO Institute of Vegetable and Tea Science, 360 Kusawa, Ano, Tsu, Mie 514-2392 Japan.
authors.forename: Akira
authors.initials: A
authors.lastname: Ando
authors.affiliation: Yeast Laboratory, National Food Research Institute, National Agriculture and Food Research Organization (NARO), 2-1-12 Kannondai, Tsukuba, Ibaraki 305-8642 Japan. Electronic address: nakamrto@affrc.go.jp.
authors.forename: Toshihide
authors.initials: T
authors.lastname: Nakamura
mesh_terms: D000612:4-Aminobutyrate Transaminase / Q000172:deficiency / Q000235:genetics; D061249:Batch Cell Culture Techniques; D001939:Bread; D005285:Fermentation; D015966:Gene Expression Regulation, Fungal; D026901:Membrane Transport Proteins / Q000172:deficiency / Q000235:genetics; D008965:Molasses; D009154:Mutation; D009584:Nitrogen / Q000378:metabolism; D010084:Oxidation-Reduction; D012441:Saccharomyces cerevisiae / Q000235:genetics* / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics* / Q000378:metabolism; D014157:Transcription Factors / Q000235:genetics* / Q000378:metabolism; D014908:Triticum; D005680:gamma-Aminobutyric Acid / Q000378:metabolism*
chemical_list: C067023:DAL81 protein, S cerevisiae; C515373:DUR3 protein, S cerevisiae; D026901:Membrane Transport Proteins; D029701:Saccharomyces cerevisiae Proteins; D014157:Transcription Factors; D005680:gamma-Aminobutyric Acid; D000612:4-Aminobutyrate Transaminase; C558424:UGA1 protein, S cerevisiae; D009584:Nitrogen
keywords: Baker's yeast; Bread dough; Fermentation; GABA; Nitrogen metabolism