BROTH LEVEL

As the broth in a fermenter or bioreactor becomes more viscous and is subjected to agitation from sparging (the introduction of tiny sterilized air bubbles at the bottom of the liquid) and from mixing by the impeller, it has a tendency to foam. This can be a serious problem as the level may rise to the point where it enters the exhaust gas lines clogging the ultrafilters and possibly jeopardizing the sterile environment within the reactor. Various antifoam strategies can be employed to correct this situation, however, detection of the condition is first required. 

800H-SCRTO 801H-SCR SANITARY, CERAMIC-LINED FLOWTUBES 

Several other forms of level measurement technologies are available. One is the float and cable system, where the buoyancy of the float determines the air-broth interface boundary and the length of the cable determines the level. The density of the broth may render this measurement questionable. 

A second is hydrostatic tank gauging, where level is inferred from pressure. Again, density, particularly if two phases exist (aqueous and foam), may render this approach questionable. 

A third is sonic, which computes the distance from the device to the broth surface based on the time it takes for the sound wave initiating from the device to reflect off the surface of the air-liquid boundary and return. 

---

Duty It is required to design a stirred reactor using microcarrier-supported animal cells. The working capacity of the reactor (volume of broth) is 20 m The dispersion height to diameter ratio = 1. Disengagement volume equivalent to 1/3 of the total volume is to be provided above the broth level. Therefore, total reactor volume is 30 m and vessel diameter is 3 m. Impeller to be used is six-blade upflow pitched turbine with DIT = CIT = 0.33. 

The common indices of the physical environment are temperature, pressure, shaft power input, impeller speed, foam level, gas flow rate, liquid feed rates, broth viscosity, turbidity, pH, oxidation-reduction potential, dissolved oxygen, and exit gas concentrations. A wide variety of chemical assays can be performed product concentration, nutrient concentration, and product precursor concentration are important. Indices of respiration were mentioned with regard to oxygen transfer and are particularly useful in tracking fermentation behavior. Computer control schemes for fermentation can focus on high productiv-... 

Clark et al. [81] determined the time course of A-acetylation of primaquine by Streptomyces roseochromogenous and Streptomyces rimosus by quantitative high performance liquid chromatographic analyses of the culture broths. The A-5-bistri-fluoroacetyl derivative of primaquine was used as an internal standard in the analysis for the quantitation of primaquine A-acetate in microbial culture broths. S. roseochromogenous forms the highest level of primaquine A-acetate at 24—36 h after substrate addition, while S. rimosus is slower in its acetylation, peaking at 3 days after substrate addition. The formation of a novel dimeric compound from the reaction of primaquine with 8-(4-phthalimido-l-methylbutylamino)-6-methoxy quinoline is also reported. 

Finally, ion chromatography is sometimes used for process applications, allowing for the tracking of the manufacturing process in order to optimize process variables and to allow for better control of process parameters. One example of this is the application of ion chromatography to the analysis of fermentation broths. Here ion chromatography is used both to measure the level of ionic nutrients in the fermentation broth in order to control the fermentation process and also to measure the level of fermentation by-product ions which may be indicative of problems with the fermentation process. 

During a more controlled study carried out within an environment artificially contaminated with high levels of individual nebulized spores of Bacillus subtilis [2], a level of contamination within the environment was achieved which led to the contamination of broth-filled units. The results were extrapolated to suggest a contamination rate of 1 unit in 4 X 10 with a smrounding environmental contamination of 1 cfu/ml... 

Extensive process simulation (broth fill) results for BFS effectively demonstrate that high levels of sterility confidence can be obtained with a properly configured and validated machine. However, in order to maintain high levels of sterility assurance, it is important that levels of microbial contamination are controlled within the filling environment. 

There is no appropriate defined sterility confidence level which can be translated directly into acceptance criteria for broth fill contamination for BFS processes. The most commonly recognized acceptance criterion is a sterility assurance level (SAL) of 10 although modem aseptic filling techniques such as BFS can achieve a higher SAL. This should be reflected by broth fill results and acceptance criteria for this advanced technology. 

Broth fills should be earried out under conditions that are representative of those during normal operation. A deviation from routine processes should only be in the direction of presenting a higher rather than a lower challenge to the proeess. Due to the level of automation of BPS teehnology, it is extremely diffieult to take extra care in order to reduee the ehanee of container contamination during a broth fill, and results are therefore not as operator dependent as other less automated aseptie manufacturing processes. 

Por a new facility, some baekground environmental monitoring data are desirable. It is important that environmental monitoring data are obtained during the eourse of broth fill batches to demonstrate a normal level of environmental contamination. The validity of broth fills earried out in an environment of consistently lower contamination levels than those obtained during routine bateh manufacture eould be questioned. 

Figure 5. Production of subtilisin. A culture of B.subtilis was grown in supplemented nutrient broth (75) and subtilisin production was followed. T-0 indicates the time of first departure from logarithmic growth. Subtilisin levels are indicated as arbitrary units/ml.

Properties of the Thermoanaerobacter sp. CGTase. The CGTase is produced extracellularly at 70 C in a prereduced liquid maltrin medium under argon. The maximal activity level after 40 hours of cultivation is 200 Phadebas units per liter culture broth. 

Immiscible combinations are all around us. Oil and water is an immiscible combination as is the lava in the so-called lava lamps and chicken broth in chicken soup. Immiscible blends are actually a misnaming at the molecular level since they are not truly mixed together. But at the macrolevel they appear mixed, so the name immiscible blends. 

---