title: Potent L-lactic acid assimilation of the fermentative and heterothallic haploid yeast Saccharomyces cerevisiae NAM34-4C.
abstract: We screened an industrial thermotolerant Saccharomyces cerevisiae strain, KF7, as a potent lactic-acid-assimilating yeast. Heterothallic haploid strains KF7-5C and KF7-4B were obtained from the tetrads of the homothallic yeast strain KF7. The inefficient sporulation and poor spore viability of the haploid strains were improved by two strategies. The first strategy was as follows: (i) the KF7-5C was crossed with the laboratory strain SH6710; (ii) the progenies were backcrossed with KF7-5C three times; and (iii) the progenies were inbred three times to maintain a genetic background close to that of KF7. The NAM12 diploid between the cross of the resultant two strains, NAM11-9C and NAM11-13A, showed efficient sporulation and exhibited excellent growth in YPD medium (pH 3.5) at 35°C with 1.4-h generation time, indicating thermotolerance and acid tolerance. The second strategy was successive intrastrain crosses. The resultant two strains, KFG4-6B and KFG4-4B, showed excellent mating capacity. A spontaneous mutant of KFG4-6B, KFG4-6BD, showed a high growth rate with a generation time of 1.1 h in YPD medium (pH 3.0) at 35°C. The KFG4-6BD strain produced ascospores, which were crossed with NAM11-2C and its progeny to produce tetrads. These tetrads were crossed with KFG4-4B to produce NAM26-14A and NAM26-15A. The latter strain had a generation time of 1.6 h at 35°C in pH 2.5, thus exhibiting further thermotolerance and acid tolerance. A progeny from a cross of NAM26-14A and NAM26-15A yielded the strain NAM34-4C, which showed potent lactic acid assimilation and high transformation efficiency, better than those of a standard laboratory strain.
authors.affiliation: Department of Applied Microbial Technology, Faculty of Biotechnology and Life Science, Sojo University, 4-22-1 Ikeda, Kumamoto 860-0082, Japan.
authors.forename: Masataka
authors.initials: M
authors.lastname: Tomitaka
authors.affiliation: Department of Applied Microbial Technology, Faculty of Biotechnology and Life Science, Sojo University, 4-22-1 Ikeda, Kumamoto 860-0082, Japan.
authors.forename: Hisataka
authors.initials: H
authors.lastname: Taguchi
authors.affiliation: Department of Applied Microbial Technology, Faculty of Biotechnology and Life Science, Sojo University, 4-22-1 Ikeda, Kumamoto 860-0082, Japan.
authors.forename: Masayoshi
authors.initials: M
authors.lastname: Matsuoka
authors.affiliation: Graduate School of Science and Technology, Kumamoto University, 2-39-1 Kurokami, Chuo-ku, Kumamoto City, Kumamoto 860-0862, Japan.
authors.forename: Shigeru
authors.initials: S
authors.lastname: Morimura
authors.affiliation: Graduate School of Science and Technology, Kumamoto University, 2-39-1 Kurokami, Chuo-ku, Kumamoto City, Kumamoto 860-0862, Japan.
authors.forename: Kenji
authors.initials: K
authors.lastname: Kida
authors.affiliation: Department of Applied Microbial Technology, Faculty of Biotechnology and Life Science, Sojo University, 4-22-1 Ikeda, Kumamoto 860-0082, Japan. Electronic address: akamatsu@lime.ocn.ne.jp.
authors.forename: Takashi
authors.initials: T
authors.lastname: Akamatsu
mesh_terms: D003433:Crosses, Genetic; D004271:DNA, Fungal / Q000235:genetics; D005285:Fermentation; D006238:Haploidy; D006358:Hot Temperature; D019344:Lactic Acid / Q000378:metabolism*; D009154:Mutation / Q000235:genetics; D016133:Polymerase Chain Reaction; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D013172:Spores, Fungal / Q000502:physiology*; D013312:Stress, Physiological; D014170:Transformation, Genetic
chemical_list: D004271:DNA, Fungal; D019344:Lactic Acid
keywords: Fuel ethanol; Heterothallic haploid; Industrial yeast; Potent lactic acid assimilation; Saccharomyces cerevisiae; Stress tolerant