Fermentor oxygen transfer

It is for this reason that the gas-phase resistance can be neglected for oxygen transfer in aerobic fermentors. 

Figure 7.6 Dynamic measurement of k a for oxygen transfer in fermentors. by...

Yeast cells are cultivated under aerobic conditions at 30 C in an aerated stirred-tank fermentor where air (21 vol% of oxygen) is supplied at a superficial gas velocity of 50 mh . The overall volumetric coefficient for oxygen transfer based on the liquid phase concentration is 80 h T... 

Gas-liquid mass transfer plays a very important role in aerobic fermentation. The rate of oxygen transfer from the sparged air to the microbial cells suspended in the broth or the rate of transfer of carbon dioxide (produced by respiration) from the cells to the air often controls the rate of aerobic fermentation. Thus, a correct knowledge of such gas-liquid mass transfer is required when designing and/or operating an aerobic fermentor. 

Estimate the liquid-phase volumetric coefficient of oxygen transfer for a stirred-tank fermentor with a diameter of 1.8 m, containing a viscous non-Newtonian broth, with consistency index K = 0.39, flow behavior index n = 0.74,... 

Estimate the liquid-phase volumetric coefficient of oxygen transfer for a bubble column fermentor, 0.8 m in diameter 9.0 m in height (clear liquid), containing the same liquid as in Problem 12.2. The superficial gas velocity is 150 m h . ... 

The advantages of the shallow-tray fermentor are the simplicity of its construction and the low investment involved. In a shallow-tray fermentor, the oxygen transfer in the solid bed occurs primarily by diffusion instead of forced convection [29]. The thickness of the solid substrate layer in the tray is, there-... 

A column fermentor is a fixed-bed reactor. Solid medium is put into the column with entries at both ends for aeration [58-60]. Figure 5 shows an experimental apparatus developed by Saucedo-Castaneda et al. [28]. Sterile air can be supplied either by a radial or axial gradient method. The water activity is maintained by humidified air. The temperature for the solid fermentation is monitored and controlled by recycling water in the jacket from an isothermal bath. In a fixed-bed column fermentor, the oxygen transfer and CO2 dissipation are im-... 

Bioreactors that use enzymes but not microbial cells could be regarded as fer-mentors in the broadest sense. Although their modes of operation are similar to those of microbial fermentors, fed-batch operation is not practiced for enzyme reactors, because problems such as excessive cell growth rates and resultant high oxygen transfer rates do not exist with enzyme reactors. The basic equations for batch and continuous reactors for enzyme reactions can be derived by combining material balance relationships and the Michaelis-Menten equation for enzyme reactions. 

The batch xylitol fermentations conducted in the bench-scale fermentors were more typical of studies on inhibitor toxicities at high cell densities. It is possible that the xylitol production phase could also be considered at the microscale (100- to 200- xl volume), as this is a microaerophilic process in which low oxygen transfer rates are desirable. While this may not provide an accurate measure of the maximum volumetric productivity for a particular hydrolysate, it may be useful for investigating fundamental toxicological effects and inhibitor synergies on xylitol production. 

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