Aeration and Agitation

One of the most important factors to consider in designing a fermenter is the provision for adequate mixing of its contents. The main objectives of mixing in fermentation are to disperse the air bubbles, to suspend the microorganisms (or animal and plant tissues), and to enhance heat and mass transfer in the medium. 

Radial-flow impellers (paddles and turbines) produce flow radially from the turbine blades toward the side of the vessel, where 

Transfer from bulk gas in a bubble to a relatively unmixed gas 

Diffusion through the relatively unmixed liquid layer surrounding the bubble 

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These machines provide mechanical agitation and aeration by means of a rotation impeller on an upright shaft. In addition, the Agitair and Denver ceUs also utilize air from a blower to help aerate the pulp. 

After seeding the nutrient medium with the preformed inoculum previously described, the mixture was subjected to agitation and aeration under aseptic conditions for 72 hours at 27°C to 28°C for the first 24 hours, then at 25°C to 26°C for the next 48 hours during this period, the pH was in the range of 6.4 to 6.8. Aeration was accomplished by cultivation under submerged conditions at an air flow rate of one volume of air per volume of medium per minute. After termination of the process, the mycelium was removed by filtration and the filtered broth found to contain 450 7of oleandomycin per ml of solution. 

These variations are sometimes caused by changes in sterilising conditions, agitation and aeration, temperature, pH, pressure and liquid level. This is why the parameters have to be controlled in a proper way using predse equipment... 

Calculate the gas hold-up for an agitated and aerated system with power input of 18 hp in an 80 m3 vessel with gas superficial velocity of 2.6 m-rniif1. 

High agitation and aeration cause major problems such as foaming, which may lead the fermentation vessel to unknown contamination. Antifoam cannot be always added for the reduction of foam it may have inhibitory effects on the growth of microorganisms, so the simplest devices have rakes mounted on the stirrer shaft and located on the surface of the fluid. 

For the agitated and aerated vessel, the ratio of power requirements for aerated versus non-aerated systems is expressed by a dimensionless number known as the aeration rate the value is obtained from Figure 6.7. 

It is well understood that mixing and mass transfer are affected by agitation and aeration rates. Typically, in an agitated vessel, the working volume is about 75% of nominal CSTR volume. 

By enrichment culture technique, a bacterium was isolated from local sewage sludge, utilising caryophyllene as the sole source of carbon and energy [103]. Fermentation of / -pinene by this culture in a mineral salt medium (Seuberf s medium) at 30°C with agitation and aeration for four days yielded a few neutral and acidic transformation products. The metabolites isolated and identified were camphor (2), bomeol (1),... 

Steps 3 and 5, the diffusion through the relatively unmixed liquid layers of the bubble and the microorganism, are the slowest among those outlined previously and, as a result, control the overall mass-transfer rate. Agitation and aeration enhance the rate of mass transfer in these steps and increase the mterfacial area of both gas and liquid. 

The third section deals with engineering principles of bioprocess. The chapter 8 deals with sterilization process and its engineering considerations (up stream process). The ninth chapter includes agitation and aeration in cellular growth and its impact on designing the bioreactors. The last chapter deals with brief introduction to down stream processing. 

Most of the research on bacteria from the genus Rhizobium is conducted in the field of genetics and bacteria-host plant simbiotic interactions. Little is known about the production of extracellular polysaccharides produced by Rhizobium as well as their properties in solution in particular, no studies have been conducted on the effect of substrate concentration, agitation, and aeration as relevant parameters to monitor in the process of exopolysaccharide (EPS) production. The present work aimed to determine the extent to which some variables affect the production of polysaccharides by Rhizobium sp. 

This culture medium has a pH of 6.15. It is sterilised by passage of steam at 122°C for 40 minutes. After cooling, the volume of the broth is 120 liters and the pH is 7.20. The medium is then seeded with 200 cc of a culture of the strain Streptomyces 31723. The culture is carried out for 27 hours at 26°-27°C with agitation and aeration with sterile air. It is then suitable for seeding the production culture. The production culture is carried out in an 800 liter formentation vessel charged with the following ... 

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