Continuous fermentations

A typical bourbon fermentation continues for 72 hours at a fermentation temperature within the 31—35°C range. Many fermentation vessels are equipped with agitation and/or cooling coils that facHitate temperature control. Significant increases in yeast numbers occur during the first 30 hours of fermentation. Over 75% of the carbohydrate is consumed and converted to ethanol. Within 48 hours, 95% or more of the ethanol production is complete. 

In oyster heart, in Mytilus, and other bivalves as well, aspartate occurs at high (about 15 /imol g 1) concentrations in the normoxic state. In anoxia (figure 3.9) the bulk of the aspartate is fermented to succinate, a process that is particularly important during early states of anoxia. At this time, it is probably redox-coupled to glycolysis. Thus the energy yield increases by 1 mole ATP per mole aspartate fermented to succinate, or by 2 moles ATP per mole aspartate if the fermentation continues to the level of propionate, and the maximum total energy yield becomes 8 moles ATP per mole glucose plus aspartate fermented to propionate. 

Boyaval P, Terre S, and Corre C. Production d acide lactique a partir de permeat de lactoserum par fermentation continue en reacteur a membrane. Le Lait 1988 68 65-84. 

In addition to SSF systems, several other advanced technologies have been incorporated in yeast fermentations. Continuous fermentation with immobi-... 

L-Camitine is used in infant health, sport and geriatric nutrition. The biotransformation is catalyzed by carnitine dehydratase in whole cells (Fig. 19-36). (R)-camitine is produced with > 99.5% conversion of butyrobetaine and > 99.5% ee. The mutant strain has blocked the L-carnitine dehydrogenase and excretes the accumulated product. The purified enzyme could not be used for the biotransformation because of its high instability. Apart from usual batch fermentations, continuous production... 

As the optimum fermentation is achieved, the leaf mass is dried or fired to inactivate the enzymes and halt the fermentation. Continuous driers are usually used, in which hot air is generated by electrical heater or coal furnace. In this process, the leaf turns dark brown or black, the aroma changes to floral, and the moisture is reduced to less than 6%. 

In either case the fermentation continues until the alcohol concentration reaches 12-13%. At that point the yeast "stews in its own juices" That is, 12-13% ethanol lolls the yeast cells that produce it. This points out a last generalization about fermentations. The stable fermentation end product, whether it is lactate or ethanol, eventually accumulates to a concentration that is toxic to the organism. Muscle fatigue is the early effect of lactate buildup in the working muscle. In the same way, continued accumulation of the fermentation product can lead to concentrations that are fatal if there is no means of getting rid of the... 

For enhanced scaled-up cyclosporin production, a modified sporulation/immobili-zation method has been proposed, increasing the cyclosporin yield up to tenfold, compared to suspended culture techniques [106]. The immobilization of cells on celite carrier beads decreases the culture s viscosity and therefore increases the mass transfer. It is possible to run the fermentation continuously since the fungal spores can be trapped in the fermenter vessel to populate and germinate on freshly added beads. 

The ABE fermentation process was first developed by C. Weizmann at Manchester University in 1912. Commercial production quickly spread to the United States and then worldwide during the First and Second World Wars first to produce acetone for ammunitions and then later to produce butanol for paint lacquers. The fermentation process fell out of favor in the United States and Europe in the 1950s when renewable solvents could no longer compete with their synthetic equivalents on price. Some production, via fermentation, continued in China, Russia, and South Africa until the early 1980s [54]. 

Cell-disrupt, centrifuge-by-settling, depth-filter, diafilter, ferment, ferment-continuously, microfilter, sterilize, transfer-through-sterilizer, ultrafilter... 

The case (c) of batch fermenter/continuous reservoir dialysis culture can be evaluated similarly. The behavior is also shown in Fig. 6.49, and the properties are analogous to those in case (b). Linear growth can be maintained, because Sres is constant due to membrane diffusion. 

A fermenter containing a sterile medium at pH 4.9 made from commercial dextrose and corn steep inoculated with Helicostylum piriforme Bain (A.T.G.G. 8992), after 24 hrs. of vigorous agitation and aeration at 28° 11, 21-dihydroxy-pregna-4,17(20)-dien-3-one in acetone added, and the fermentation continued for 2 days 9a,21-dihydroxypregna-4,l7(20)-diene-3,11-dione. Y 59.0%. A. R. 

Stuck fermentation continues to be a much discussed subject. In some cases, a modification of vine varieties has produced grapes that have high sugar concentrations. These grapes are more difficult to ferment than past varieties. In other cases, winemakers have recently realized that sluggish fermentations spread over several months are not ideal for making wine. 

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