Effect of Vitreoscilla hemoglobin expression on the growth of Bacillus subtilis natto and its production of γ-poly-glutamic acid
| Autor: | Wan-Ru Lin, 林宛儒 |
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| Rok vydání: | 2005 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 93 Poly(γ-glutamic acid) (γ-PGA) is produced by bacillus species as an extracellular polymer. The accumulation of γ-PGA in the culture medium causes a significant viscosity increase that reduces cell biomass and γ-PGA production yield. The reduction of γ-PGA production was attributed to the limited O2 supply which resulted from the high medium viscosity. Bacterial hemoglobin (Vitreoscilla Hemoglobin, VHb) is known to enhance in vivo oxygen concentration in a oxygen-limited culture. In this study, we introduced an expression cassette which contains a constitutive promoter PS10 controlled VHb gene into a γ-PGA producing strain. Bacillus subtilis natto to improve its growth and γ-PGA production. VHb gene was integrated into the chromosome by homologous recombination through the amylase gene. The expression of VHb did increase the γ-PGA concentration during the shaker flask cultivation. However, the transformant like the wild type Bacillus subtilis natto strain showed very poor γ-PGA productivity after several generation of cultivation. The VHb gene was still detectable in the transformant of poor performance. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
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