title: Mitochondrial metabolism and stress response of yeast: Applications in fermentation technologies.
abstract: Mitochondria are sites of oxidative respiration. During sake brewing, sake yeasts are exposed to long periods of hypoxia; the structure, role, and metabolism of mitochondria of sake yeasts have not been studied in detail. It was first elucidated that the mitochondrial structure of sake yeast transforms from filamentous to dotted structure during sake brewing, which affects malate metabolism. Based on the information of yeast mitochondria during sake brewing, practical technologies have been developed; (i) breeding pyruvate-underproducing sake yeast by the isolation of a mutant resistant to an inhibitor of mitochondrial pyruvate transport; and (ii) modifying malate and succinate production by manipulating mitochondrial activity. During the bread-making process, baker's yeast cells are exposed to a variety of baking-associated stresses, such as freeze-thaw, air-drying, and high sucrose concentrations. These treatments induce oxidative stress generating reactive oxygen species due to mitochondrial damage. A novel metabolism of proline and arginine catalyzed by N-acetyltransferase Mpr1 in the mitochondria eventually leads to synthesis of nitric oxide, which confers oxidative stress tolerance on yeast cells. The enhancement of proline and arginine metabolism could be promising for breeding novel baker's yeast strains that are tolerant to multiple baking-associated stresses. These new and practical methods provide approaches to improve the processes in the field of industrial fermentation technologies.
authors.affiliation: Department of Environmental Sciences, Faculty of Agriculture, Saga University, 1 Honjo-cho, Saga 840-8502, Japan; Department of Biochemistry and Applied Biosciences, United Graduate School of Agricultural Sciences, Kagoshima University, Korimoto1-21-24, Kagoshima 890-8580, Japan. Electronic address: ktgkhrs@cc.saga-u.ac.jp.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Kitagaki
authors.affiliation: Graduate School of Biological Sciences, Nara Institute of Science and Technology, 8916-5 Takayama, Ikoma, Nara 630-0192, Japan.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Takagi
mesh_terms: D000434:Alcoholic Beverages / Q000382:microbiology; D001120:Arginine / Q000378:metabolism; D003890:Desiccation; D005285:Fermentation; D005615:Freezing; D008293:Malates / Q000378:metabolism; D008928:Mitochondria / Q000378:metabolism*; D009569:Nitric Oxide / Q000378:metabolism; D010084:Oxidation-Reduction; D018384:Oxidative Stress; D011392:Proline / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism; D013312:Stress, Physiological; D019802:Succinic Acid / Q000378:metabolism; D015003:Yeasts / Q000166:cytology* / Q000378:metabolism*
chemical_list: D008293:Malates; D017382:Reactive Oxygen Species; D009569:Nitric Oxide; C030298:malic acid; D001120:Arginine; D011392:Proline; D019802:Succinic Acid
keywords: Baker's yeast; Bread making; Mitochondrial metabolism; Nitric oxide; Organic acids; Oxidative stress; Proline-arginine metabolism; Sake brewing; Sake yeast; Stress tolerance