Isolation of sake yeast strains possessing various levels of succinate- and/or malate-producing abilities by gene disruption or mutation
ABSTRACT Succinate and malate are the main taste components produced by yeast during sake (Japanese alcohol beverage) fermentation. Sake yeast strains possessing various organic acid productivities were isolated by gene disruption. Sake fermented using the aconitase gene (ACO1) disruptant contained a two-fold higher concentration of malate and a two-fold lower concentration of succinate than that made using the wild-type strain K901. The fumarate reductase gene (OSM1) disruptant produced sake containing a 1.5-fold higher concentration of succinate as compared to the wild-type, whereas the α-ketoglutarate dehydrogenase gene (KGD1) and fumarase gene (FUMI) disruptants gave lower succinate concentrations. The Δkgd1 disruptant exhibited lower succinate productivity in the earlier part of the sake fermentation, while the Δfum1 disruptant showed lower succinate productivity later in the fermentation, indicating that succinate is mainly produced by an oxidative pathway of the TCA cycle in the early phase of sake fermentation and by a reductive pathway in the later phases. Sake yeasts with low succinate productivity and/or high malate productivity was bred by isolating mutants unable to assimilate glycerol as a carbon source. Low malate-producing yeasts were also obtained from phenyl succinate-resistant mutants. The mutation of one of these mutant strains with low succinate productivity was found to occur in the KGD1 gene. These strains possessing various succinate- and/or malate-producing abilities are promising for the production of sake with distinctive tastes.
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ABSTRACT: Our Photonics Group in NICHe, Tohoku University, is unique in Japanese Universities in several points: . In NICHe, I am engaged in: (1) Research activity of photonic crystals ranging from basic electromagnetic theory to practical applications. I gave an invited talk on photonic crystals in this conference. It covers my work in the research phase. (2) Pre-Venture project sponsored by Japan Science and Technology Association (JST). The aim of the project is to help university people to start up a high-tech company exploiting the strength of each team. In this rump session, I focus on what we are doing and will do during/after the "pre-venture" project01/2001;
- Kagaku To Seibutsu. 01/2000; 38(1):30-36.
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ABSTRACT: J. Inst. Brew. 114(2), 97-101, 2008 A collection of Saccharomyces cerevisiae strains deficient in the tricarboxylic acid cycle enzymes activities has been examined for the production of beer with reduced ethanol content. Strains deficient in fumarase and α-ketoglutarate dehydrogenase en- coded by the genes FUM1 (0.48%), KGD1 (0.42%) and KGD2 (0.48%) made non-alcoholic beers with an alcohol content lower than 0.5% (v/v). The rest of the yeast mutants also gave rise to low-alcoholic beers but with a slightly elevated ethanol con- centration (mostly in the range of 0.57-0.84% and 1.64% for the lip5 mutant). Low ethanol content was compensated by the con- siderable increase of organic acids (citrate succinate, fumarate, and malate). In addition, some of the mutants released high lev- els of lactic acid (144 (fum1), 622 (kgd1) and 495 (kgd2) mg/L). Lactic acid protects beers against contamination and masks an unacceptable worty off-flavour.Journal of the Institute of Brewing. 01/2008; 114(2).