Effect of Vitreoscilla hemoglobin expression on the growth of Bacillus subtilis natto and its production of γ-poly-glutamic acid
碩士 === 國立臺灣科技大學 === 化學工程系 === 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 product...
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| Format: | Others |
| Language: | zh-TW |
| Published: |
2005
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| Online Access: | http://ndltd.ncl.edu.tw/handle/66343689771892577590 |
| Summary: | 碩士 === 國立臺灣科技大學 === 化學工程系 === 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.
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