Growing E. coli to high cell density--a historical perspective on method development.

(1972). Activity, Ecology, and Population Dynamics of Microorganisms in Soil. CRC Critical Reviews in Microbiology: Vol. 2, No. 1, pp. 59-137.

Activity, ecology, and population dynamics of microorganisms in soil.

In lactic acid fermentation by Lactobacillus delbrueckii, the produced lactic acid affected the lactic acid productivity. Therefore, for the purpose of alleviating this inhibitory effect, an electrodialysis fermentation method which can continuously remove produced lactic acid from the fermentation broth was applied to this fermentation process. As a result, the continuation of fermentation activity was obtained, and the productivity was three times higher than in non-pH-controlled fermentation. In electrodialysis fermentation, the amount of produced lactic acid was 82.2 g/liter, which was about 5.5 times greater than that produced in non-pH-controlled fermentation. It was concluded that these good results were obtained on account of alleviating the lactic acid inhibitory effect by electrodialysis fermentation. However, the fouling of anion-exchange membranes by cells was observed in electrodialysis fermentation.

Novel Method of Lactic Acid Production by Electrodialysis Fermentation

Lactose of sweet whey permeate was converted into sodium lactate byLactobacillus helveticus. To increase the, productivity of the lactic acid fermentation and to reduce the amounts of effluents, the bioreactor was coupled with an ultrafiltration module and an electrodialysis unit. Without the electrodialyzer, with total cell recycling and at a dilution rate of 0.88 h−1, a cellular concentration of 64 gl−1 and a productivity of 22 gl−1 h−1 were obtained. When the electrodialysis unit is coupled, the outlet concentration of lactate was stabilized at 85±5 gl−1.

Continuous lactic acid fermentation with concentrated product recovery by ultrafiltration and electrodialysis

The application of immobilized cell systems for the production of ethanol has resulted in substantial improvements in the efficiency of the process when compared to the traditional free cell system. In this review, the various methods of cell immobilization employed in ethanol production systems have been described in detail. Their salient features, performance characteristics, advantages and limitations have been critically assessed. More recently, these immobilized cell systems have also been employed for the production of ethanol from non-conventional feedstocks such as Jerusalem artichoke extracts, cheese whey, cellulose, cellobiose and xylose. Ethanol production by immobilized yeast and bacterial cells has been attempted in various bioreactor types. Although most of these studies have been carried out using laboratory scale prototype bioreactors, it appears that only fluidized bed, horizontally packed bed bioreactors and tower fermenters may find application on scale-up. Several studies have indicated that upon immobilization, yeast cells performing ethanol fermentation exhibit more favourable physiological and metabolic properties. This, in addition to substantial improvements in ethanol productivities by immobilized cell systems, is indicative of the fact that future developments in the production of ethanol and alcoholic beverages will be directed towards the use of immobilized cell systems. 291 references.

Advances in ethanol production using immobilized cell systems

Gerhardt, Philipp (The University of Michigan, Ann Arbor), and D. M. Gallup. Dialysis flask for concentrated culture of microorganisms. J. Bacteriol 86:919-929. 1963.-A twin-chambered dialysis flask was designed with a supported membrane clamped between a reservoir of medium in the bottom and a small volume of culture above, the unit being mounted on a shaking machine to provide aeration and agitation. The performance of different dialysis membranes and membrane filters was compared in glucose-diffusion and bacterial-culture tests. Some of the variables in dialysis culture were assessed and the growth response was characterized, with Serratia marcescens as the test organism. The general usefulness and concentrating effect of dialysis culture were demonstrated in trials with 16 representative types of microorganisms. Dialysis culture was shown to be especially suitable for producing dense populations of cells or their macromolecular products in an environment free from complex medium constituents, for removing toxic products that limit growth or fermentation, and for supplying oxygen by diffusion without the damage from usual aeration procedures.

Dialysis flask for concentrated culture of microorganisms

Cell-mass production of Serratia marcescens was studied in dialysis systems in which growth was managed in a fermentor remote from, but connected by conduits and pumps with, a nutrient reservoir. Dialysis was accomplished with membrane tubing in either the fermentor or the reservoir, or best with membrane sheet in a plate-and-frame dialyzer that was remote from but connected with both vessels. Growth trials with these systems demonstrated their ability to produce virtually unlimited population density in a liquid culture, viable counts in excess of 1012 cells/ml and partial cell volume of 50% being attained. The system used for growth also may be used, after the growth cycle, to concentrate cells still further by osmotic dehydration with a hydrophilic colloid. The dialyzer-dialysis system that was evolved permits independent control of the component operations and is believed to be adaptable to any desired scale of size.

D. M. Gallup

Papers

Dialysis flask for concentrated culture of microorganisms

Dialysis Fermentor Systems for Concentrated Culture of Microorganisms.