Fermentation systems tower

Cells for Increasing Fermenter Efficiencies. The tower fermenter system used is described in Figure 3. Wort was used as the ethanol source, and an inociilum of an aggregating strain of Acetobacter species was prepared and added to the tower fermenter (2 litres capacity). When the level of acetic acid in the fermenter had reached about 3% w/v, the medium delivery pump was started and the flow rate adjusted to a level that gave almost complete conversion of the ethanol available into acetic acid. Undue haste in increasing the flow rate and also serious decrease or stoppage of the air flow caused the expected fall in conversion efficiency. Adjustment of the flow and aeration rate showed that a maximum V. E. of 0.82 could be attained (see Table I). 

It is unnecessary to recycle yeast if a sedimentary strain of yeast is used. (Fig. 19.19). Very high yeast concentrations may be achieved by the use of inclined tubes, still zones around outlet pipes and by holding the yeast in a filter. Growth of the sedimentary yeast may be controlled by the amount of air injected, while carbon dioxide is used to cause some mixing. Parallel to these developments is the tower fermenter system [58, 61, 71] which comprises a vertical tube into the base of which wort is pumped (Fig. 19.21). 

Commercial-scale operations are conducted in batch, fed-batch, or continuous culture systems. Fermentation vessels include the conventional baffled aerated tank, with or without impeller agitation, and the ak-lift tower fermentors in which ak is sparged into an annular space between the... 

Continuous ethanol fermentation using a tower fermentor with high floccu-lent yeast strains has been studied in depth (see [13] for pertinent references). Overall, the system has the following characteristics ... 

The case study is based on a tower-type bioreactor that uses S. cerevisiae immobilized in pellets with 4% of citric pectin, for production of bioethanol. The bioreactor is divided in four stages with gas separators between them to prevent the CO2 accumulation during the fennentation process because the CO2 release may eventually result in a drop in the fermentation yield. The experiments were performed at 30 °C, pH 4.0, initial substrate concentration of 161.4 g/L, feed flow rate of 40 mL/h, and residence time of 6.12 h. After 40 h of operation, the system has reached a steady state. A diagram of the system is shown in Fig. 1. 

Laboratory studies on continuous fermentation of wort by brewers yeast demonstrated that satisfactory beers could be produced only when a number of stirred fermenters were used in series (cascade system) or in tubular (tower) fermenters (Chapter 19). In both cases satisfactory throughputs were only obtained by ensuring a high concentration of yeast remained in the system. To achieve this, in a cascade system, yeast was recycled from the outflow back into the fermenter. Under such conditions in a single vessel homogeneously mixed system at steady state we have ... 

Owing to slight density differences between fermentation liquid and biomass the particles have the tendency to settle. Thus a biomass concentration profile along the tower may result. The pertinent model to account for biomass concentration profiles is the sedimentation-dispersion model (74,75). This model involves two parameters, neimely, the solid dispersion coefficient 3 and the mean settling velocity Us of the biomass particles in the swarm. Both parameters were determined by Kato et al. (75) in bubble columns for glass beads of 75 and 163 urn diameter. The authors presented their results by empirical correlations for both Eg and ug. Until other data for smaller density differences are available the application of the correlations of Kato and coworlcers is recommended for biological systems also. It should be pointed out that the solid phase dispersion coefficient Eg almost completely agrees with El i.e. the liquid phase dispersion coefficient. ... 

Continuous fermentors (Figure 12.15) comprise a 400 to 4000 hi stainless steel tower. A 4000 hi system can handle 130 metric tons of harvest per day and it can produce approximately 23 000 hi of wine in 3 weeks. An annual wine production of 40 000 hi is necessary to justify the costs of such a system. These fermentors permit the daily reception of fresh grapes and the evacuation of an equivalent amount of partially fermented wine and skins. In the upper part, a rotating rake removes the... 

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