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KMID : 1094720100150040635
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Biotechnology and Bioprocess Engineering
2010 Volume.15 No. 4 p.635 ~ p.640
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Effect of aeration and agitation on synthesis of poly (γ-glutamic acid) in batch cultures of Bacillus licheniformis NCIM 2324
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Bajaj Ishwar B.
Singhal Rekha S.
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Abstract
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The effects of aeration and agitation on the production and molecular weight of poly (γ-glutamic acid) (PGA) were systematically investigated in batch fermentor cultures of Bacillus licheniformis NCIM 2324. A high aeration rate and agitation speed enhanced the growth of B. licheniformis NCIM 2324, but did not always lead to high PGA production. Additionally, PGA production actually decreased at very high aeration rates and agitation speeds. The maximum PGA concentration was obtained at 750 rpm and 1 vvm. Rheological studies revealed that fermentation broth during production of PGA exhibited pseudoplastic behavior. The effects of aeration and agitation on the molecular weight of PGA were also studied, and the rate and extent of the decrease in the molecular weight of PGA as a function of time were found to be much greater at high aeration than low aeration. The PGA production of 46.34 g/L with a specific productivity of 0.17 g-PGA/g-biomass/ h and a PGA yield of 0.48 with respect to total substrate observed in the present study are much higher than the values reported in previously conducted studies.
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KEYWORD
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Poly (γ-glutamic acid), biopolymer, agitation, aeration, rheology, molecular weight
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