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  1. 2 Biotechnologia

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  1. 2 2004

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  1. 2 Podgorski W.

  2. 1 Lesniak W.

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1

On-line monitoring of A. niger metabolic activity in biotransformation of glucose to gluconic acid

100%
Podgorski W.
Biotechnologia
|
2004
|
issue 1
169-186
EN
Control parameters directly connected with metabolism of microorganism that reflect its actual activity in gluconic acid biosynthesis can be chosen basing on mass balance of the process. The relatively high correlation between parameters, normally determined via sample analysis and microorganisms? respiratory activity, enabled on-line estimation of biomass growth, product formation, and substrate uptake rate. The estimated parameters were continuously measured and employed to on-line control of gluconic acid overproduction by Aspergillus niger W78B strain. The application of the noninvasive technique for parameters determinations allowed obtaining high effectiveness of product formation characterized by the yield coefficient that equals 1.0 g g-1 and product formation rate amounted to 5 g dm-3 h-1. The estimation of the parameters cannot be used instead of their quantitative determinations, but it gives a possibility of on-line monitoring and control of the process.
2

Oxygen transfer during citric acid biosynthesis in 7 and 15 000 liters stirred tank reactors

63%
Podgorski W., Lesniak W.
Biotechnologia
|
2004
|
issue 1
187-200
EN
In laboratory scale, submerged citric acid fermentation enabled to obtain similar to the industrial bioreactor volumetric oxygen transfer rate (kLa) amounted to 240 h-1. Nevertheless, such level of kLa seems not to be necessary for the process. Bioreactors used for the production of citric acid using Aspergillus niger W78B strain, assuring kLa at the 120 h-1 level in a overproduction phase, allowed achieving the oxygen uptake rate by cells in the range 12-15 mmol dm-3 h-1 and a product on substrate yield factor (YP/S) higher then 0.8 g g-1. Thus, the resignation from the widespread in literature strategy of pO2 maximization as an essential prerequisite for high citric acid yield, allowed obtaining the significant 20% improvement in the yield of product formation in the case of molasses media and 7% on synthetic one. Therefore, it can be stated that excessive media aeration during submerged citric acid biosynthesis is not suitable for yield and/or cost of product formation.
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