Aeration Sparger

This material was made up with distilled water to provide 41 g per liter, and the mixture was adjusted to pH 7.0 with potassium hydroxide solution. To the mixture were added per liter 5.0 g of calcium carbonate and 7.5 ml of soybean oil. 2,000 ml portions of this medium were then added to fermentation vessels, equipped with stirrers and aeration spargers, and sterilized at 121°C for 60 minutes. After cooling the flasks were inoculated with a suspension of strain No. ATCC 11924 of Streptomyces lavendulae, obtained from the surface of agar slants. The flasks were stirred for 4 days at 28°C at approximately 1,700 rpm. At the end of this period the broth was found to contain cycloserine in the amount of about 250 C.D.U./ml of broth. The mycelium was separated from the broth by filtration. The broth had a pH of about 7.5. Tests showed it to be highly active against a variety of microorganisms. 

Aeration, sparger diffused air system including blowers (including one standby blower to ensure reliability), drives, building, air piping, air diffusers but excluding the vessel, installed cost 475 000 at reliable air flow rate of 1.4 m s, n = 0.66 for flow rate 0.05-1.4 and n = 0.93 for flow rate 1.4-23. 

Fig. 3. Commercial aerating systems. Diffused aerators utilizing (a), (b) pipes, (c) a sparger, and (d) underwater air-supply tubes (e) a mechanical aerator (f)...

A few variations on the standard fermenter have been attempted, but none has become popular. An obsolete design in which the fermenter was rotated to aerate the medium is shown in Fig. 24-5. Performance was unsatisfactory, and the units were turned on end, with spargers and agitation added. One of the largest fermenters used for antibiotics is a horizontal cylinder with several agitators, as in Fig. 24-6. Multiple agitator motors and shafts have also been used with vertical cylindiic vessels. 

Aeration of Solution Unless specified, the solution should not be aerated. Most tests related to process equipment should be run with the natural atmosphere inherent in the process, such as the vapors of the boiling liquid. If aeration is used, the specimens should not be located in the direc t air stream from the sparger. Extraneous effects can be encountered if the air stream impinges on the specimens. 

BalHca and Ryu [158] correlated reductions in cell yield in Datura stramonium suspensions with the increased Reynolds stresses associated with higher aeration rates in a 1.2-1 ALR. A more recent study [159] of C. roseus suspensions cultivated in a 1.5-1 bubble column showed that the increased bubble sizes associated with both larger sparger pores and higher aeration rates caused a reduction in system performance. Here, also, it was postulated that the effects were due to increased Reynolds shear stresses in the flow field. However, it was not possible to rule out gas-stripping effects. 

The cell culture was carried out under the following conditions temperature 30 °C pH 7.0 controlled by the addition of 2 m KOH. The fermenter was aerated at 1 vvm via a submerged sparger and the agitation rate was controlled between 600 and 1000 rpm in order to maintain the dissolved oxygen concentration above 20 % air saturation. Foaming was controlled by addition of antifoam (Mazu DF 204, BASF). 

In Figure 11.2 a schematic view of a stirred vessel is given. The vessel is cyhndrical with a height (m) and a diameter T (m). Usually is equal to or greater than 2 T. It is equipped with a stirrer in the lower compartment. TTiis stirrer is mounted near the bottom, usually at a distance equal to the stirrer diameter. At a lower position the stirrer and bottom interact, leading to a decrease in power consumption. At a higher position hquid circulation problems can occur because, at increased gas flow rate in case of aeration, the bubbles will not be recirculated in the lower compartment. Sometimes the upper compartment (s) are also equipped with a stirrer. The vessel is equipped with baffles to prevent rotation of the contents as a whole. For aeration an air sparger is mounted below the stirrer. For mass transfer... 

Birch, D J., Ahmed, N., Solids suspension in aerated agitated vessels Role of sparger design, 9th European Conference on Mixing Mixing 97, Vol. 11, 177 (1997)... 

In order to see the magnitude of the variables, consider the aeration of a cylindrical tank lm deep and 1 m diameter. Nitrogen is sparged to desorb oxygen from the liquid. Water flows continuously across the tank at a rate of 1 L/s. The nitrogen flow-rate is 0.061 kg/s, and the temperature is 20°C. The results of the outlined calculation of a suitable sparger ring, are as follows ... 

Aeration can be accomplished by allowing the liquid to fall in a thin film or to be sprayed in the form of droplets in air at atmospheric pressure or the air, under pressure, may be bubbled into the liquid by means of a sparger, or other device that creates thousands of small bubbles, thus providing maximum contact area between the air and the liquid. 

For scale-up of inoculum conditions of hairy root cultivation, a 1-L bioreactor (working volume of 800 mL) was used. This bioreactor had a height/diameter aspect ratio of 7.14. The bubble bioreactors had no internal mechanical agitation parts. The supplied aeration rate was 0.1 wm at the bottom by sparger. Each bioreactor was inoculated with 0.2-2.0 % (w/v) g fresh weight of hairy roots and cultured for 32 d. 

The aerated stirred vessel has been widely operated in chemical industries. The aim of gas-liquid mixing is to make the bubbles small in order to accelerate the mass transfer between the gas and the liquid. In the case of gas-liquid mixing, the gas that flows out from a sparger is trapped once by the impeller and then discharged as bubbles. The mixing state of the gas-liquid mixing is classified into three states ... 

Until now, bioreactors of various types have been developed. These include loop-fluidized bed [14], spin filter, continuously stirred turbine, hollow fiber, stirred tank, airlift, rotating drum, and photo bioreactors [1]. Bioreactor modifications include the substitution of a marine impeller in place of a flat-bladed turbine, and the use of a single, large, flat paddle or blade, and a newly designed membrane stirrer for bubble-free aeration [13, 15-18]. Kim et al. [19] developed a hybrid reactor with a cell-lift impeller and a sintered stainless steel sparger for Thalictrum rugosum cell cultures, and cell densities of up to 31 g L1 were obtained by perfusion without any problems with mixing or loss of cell viability the specific berberine productivity was comparable to that in shake flasks. Su and Humphrey [20] conducted a perfusion cultivation in a stirred tank bio-... 

For anthocyanin production by cell cultivation of Perilla frutescens in an agitated bioreactor, at an aeration rate of 0.1 wm using a sintered sparger, its accumulation was poor, showing almost the same result as that at 0.2 wm using a ring sparger, when the other cultivation conditions were maintained the same [23]. However, when the aeration rate was increased to 0.2 wm with the sinter-... 

Nagata (1975) showed that in aerated suspensions, a significantly higher stirrer speed and thus power consumption per unit volume is required to establish the state of complete suspension. Furthermore, the propeller normally requires a higher stirrer speed for complete suspension than the turbine. Arbiter et al. (1969) reported that drastic sedimentation of suspended particles occurs when the aeration number JVA = QJN d (here Qg is the volumetric gas flow rate) exceeds a critical value. This critical gas flow coincided with the point where the power drawn by the agitator decreased suddenly with a small increase in the gas sparger rate. Thus, an increase in gas... 

Surface aeration is usually employed for slow reactions or for batch processes. It can be used in semicontinuous systems when it is desirable to recirculate the gas from the headspace. This is frequently the case in hydrogenation and is referred to as dead-end hydrogenation. In this system, gas is fed continuously to the reactor at the rate at which hydrogen is being consumed no compression costs to overcome the static head of liquid or external recirculation is needed. Feeding gas from the headspace may be preferred when there is a possibility of plugging sparger holes with reaction products. Surface aerators are also extensively used for waste-water treatment. There are two types of surface aerators the brush aerator, and the most commonly used turbine aerator. 

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