Jean Marc Engasser

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In order to understand the role of the medium osmolality on the metabolism of glumate-producing Corynebacterium glutamicum, effects of saline osmotic upshocks from 0.4 osnol. kg−1 to 2 osmol. kg−1 have been investigated on the growth kinetics and the intracellular content of the bacteria. Addition of a high concentration of NaCl after a few hours of batch(More)
Acetone and butanol can be produced by batch and continuous culture of Clostridium acetobutylicum on a nitrogen limited synthetic medium. When cells are grown on a high glucose concentration, conversion yields close to 0.3 g solvents/g glucose are obtained at pH 5.0. The fermentation kinetics are similar in batch and continuous cultures.
A stable continuous culture of Clostridium acetobutylicum on a complex medium containing 40 g/l glucose has been maintained for two months. At an optimal dilution rate fo 0.06 h−1, the fermentation yields 13 g/l acetone-butanol-ethanol, which corresponds to a maximal productivity of 0.75 g/l.h solvents. Due to the toxic effect of butanol, the longevity of(More)
In order to determine the response of Corynebacterium glutamicum to osmotic stress under different growth conditions, the bacteria were grown in glucose-limited continuous cultures at osmotic pressures of 0.4–2.4 osmol kg−1 by addition of NaCl to the culture medium. Steady-state continuous cultures were obtained for all investigated osmotic pressures.(More)
 In order to determine the possible effect of nutrient limitations on the response of Corynebacterium glutamicum to a saline osmotic up-shock, the bacteria were grown in continuous cultures, at osmotic pressures of 0.4 osmol/kg and 1.2 osmol/kg, under ammonia and potassium limitation. At the low osmolality of 0.4 osmol/kg, the glutamate and proline levels(More)
The kinetics of a two-stage continuous fermentation of Clostridium acetobutylicum have been studied. The pH and the dilution rate have been shown to be two essential factors for process optimization. An increase in pH or dilution rate in the first stage decreased solvent production in the second fermentor. To achieve optimal solvent production, the pH had(More)
The production of solvent by Clostridium acetobutylicum was studied, using fed-batch fermentations. Different specific rates of carbohydrate utilisation were obtained by variations in feeding rates of sugar. At slow catabolic rates of sugar, addition of acetic acid or butyric acid, alone or together, increased the rate of the metabolic transition by a(More)
To maximise solvent production in a two-stage continuous culture ofClostridium acetobutylicum, a low concentration of solvents had to be maintained in the first vessel. A 19 g/l solvent concentration was achieved, if only 2 g/l acids were present in the first stage. The second stage was dependent on the metabolic state of the cells produced in the first(More)
To increase the productivity of the acetone-butanol fermentation, a hollow-fiber ultrafilter is used to separate and recycle cells in a continuous fermentation ofClostridium acetobutylicum. Under partial cell recycling and at a dilution rate of 0.5 hr−1, a cellular concentration of 20 g/l and a solvent productivity of 6.5 g/ is maintained for several(More)
A stable continuous culture has been maintained for 30 days at a high 20 g/l solvent concentration. This substantial increase in the stability of the continuous culture ofClostridium acetobutylicum at the maximal solvent level was achieved by using a two-stage process with a dilution rate of 0.1 h−1 in the first fermentor and 0.04 h−1 in the second(More)