Takeshi Hayashi

Publications (2)5.48 Total impact

• Article: Respiratory chain analysis of Zymomonas mobilis mutants producing high levels of ethanol.

  Takeshi Hayashi, Tsuyoshi Kato, Kensuke Furukawa
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  ABSTRACT: We previously isolated respiratory-deficient mutant (RDM) strains of Zymomonas mobilis, which exhibited greater growth and enhanced ethanol production under aerobic conditions. These RDM strains also acquired thermotolerance. Morphologically, the cells of all RDM strains were shorter compared to the wild-type strain. We investigated the respiratory chains of these RDM strains and found that some RDM strains lost NADH dehydrogenase activity, whereas others exhibited reduced cytochrome bd-type ubiquinol oxidase or ubiquinol peroxidase activities. Complementation experiments restored the wild-type phenotype. Some RDM strains seem to have certain mutations other than the corresponding respiratory chain components. RDM strains with deficient NADH dehydrogenase activity displayed the greatest amount of aerobic growth, enhanced ethanol production, and thermotolerance. Nucleotide sequence analysis revealed that all NADH dehydrogenase-deficient strains were mutated within the ndh gene, which includes insertion, deletion, or frameshift. These results suggested that the loss of NADH dehydrogenase activity permits the acquisition of higher aerobic growth, enhanced ethanol production, and thermotolerance in this industrially important strain.
  Applied and environmental microbiology 06/2012; 78(16):5622-9. · 3.69 Impact Factor
• Article: Respiration-deficient mutants of Zymomonas mobilis show improved growth and ethanol fermentation under aerobic and high temperature conditions.

  Takeshi Hayashi, Yoshifumi Furuta, Kensuke Furukawa
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  ABSTRACT: Respiration-deficient mutant (RDM) strains of Zymomonas mobilis were isolated from antibiotic-resistant mutants. These RDM strains showed various degrees of respiratory deficiency. All RDM strains exhibited much higher ethanol fermentation capacity than the wild-type strain under aerobic conditions. The strains also gained thermotolerance and exhibited greater ethanol production at high temperature (39°C), under both non-aerobic and aerobic conditions, compared with the wild-type strain. Microarray and subsequent quantitative PCR analyses suggest that enhanced gene expression involved in the metabolism of glucose to ethanol resulted in the high ethanol production of RDM strains under aerobic growth conditions. Reduction of intracellular oxidative stress may also result in improved ethanol fermentation by RDM strains at high temperatures.
  Journal of Bioscience and Bioengineering 01/2011; 111(4):414-9. · 1.79 Impact Factor