Continuous inhibition culture

A continuous inhibition culture will often lead to two possible steady states, as defined by the steady-state condition /< = D, as shown in Fig. 2. 

The oscillatory behavior of product-inhibited cultures cannot simply be described by a common inhibition term in the equation for the biomass growth. A better description must include an indirect or delayed effect of the product ethanol on the biomass growth rate as indicated in experiments. The decay rate pmaa was introduced to account for the accumulation of the inhibitory product pyruvic acid. Other more mechanistic, structured models can be formed that relate to the internal key-compound e. In these, the inhibitory action of ethanol is accounted for in the inhibition of the key-compound e formation. Mathematically, however, these two model descriptions are equivalent, except that the key-compound e is washed out as a part of the biomass in continuous cultures and the rate constant //ma55 does not vary. Our proposed indirect inhibition model provides a good qualitative description of the experimental results shown in Figure 7.25. 

A rapid semiautomated microdilution method for the microbiological assay of the chloroquine has been developed by Desgardins (26). Antimalarial activity of chloroquine may be studied against cultured Plasmodium falciparum, microplates are used to prepare serial dilution of the drug. Parasites obtained from continuous stock cultures are subcultured in the micro-plates for 42 h. Inhibition of uptake of a radio labeled nucleic acid precursor by parasites serves as the indicator of antimicrobial activity. 

Webster, H. K., Whaun, J. M., Walker, M. D., and Bean, T. L. (1984a). Synthesis of adenosine nucleotides from hypoxanthine by human malaria parasites (Plasmodium falciparum) in continuous erythrocyte culture Inhibition by hadacidin but not alanosine. Biochem. Pharmacol. 33,1555-1557. 

Finally, Bazua and Wilke (1977) compared different approaches to ethanol inhibition of continuous yeast cultures and concluded that observed differences in the results are caused not only by different strains but also by altering experimental conditions. They proposed a three-parameter equation... 

Autotrophic activity. Because of the low C N ratio and its declining value as carbonaceous residues are degraded there is substantial ammonification. With all mean treatment times greater than the doubling time of Nitrobacter sp. nitrification will occur provided that oxygen is not limiting. Smith and Evans (19) found that with DO levels above 15% of saturation, nitrification continued until the culture was limited by a fall in pH level. Up to 40% of the slurry ammonia was oxidised. The autotrophic activity never achieved steady state and cycled between periods of activity when the pH value was above about 5.5 and periods of inactivity when the pH value fell below 5.5. Complete nitrification of all ammonia only occurred if the pH value was controlled at about 7 by the addition of alkali. When the DO level was held within the range of 1 to 15% of saturation a system of simultaneous nitrification and denitrification was established. The reduction of nitrate allowed the pH value to remain above 6 and nitrification to continue. Thus more than 70% of the ammonia was oxidised. If the DO level was held below 0.1% of saturation, nitrification was inhibited (unpublished). 

The first steps in bypassing of the biological, technological, and financial burden of live stock culturing or maintenance were made more than 20 years ago through the development of a bacterial luminescence inhibition test [34,35] this bioassay is presently known and used worldwide as the Microtox test. The revolutionary principle of this test is that it uses a lyophihzed strain of a (marine) bacterium Photobacterium phosphoreum). This makes the bioassay apphcable anytime, anywhere, without the need for continuous culturing of the test species. 

Fig. 2. CD154 and IL-4 stimulation of CLL cells Inhibits dmg-Induced cell death. CLL cells were cultured on WT and CD154 NIH3T3 fibroblasts using either the continuous (a) or the discontinuous (b) protocol In the presence of bortezomlb (30 nM), PHA-767491 (10 pIVI), fludarablne (10 p.M), or vehicle control for 24 h. Cell death was analyzed using a BD FACSCanto I flow cytometer (BD Biosciences) using annexin V/Pi staining. Dataware analyzed using FlowJo ( Tree Star) and GraphPad Prism software.

A. General description Abciximab is the Fab fragment of the chimeric human-murine monoclonal antibody 7E3. It binds to the glycoprotein (gp) Ilb/IIIa receptor of human platelets and inhibits platelet aggregation. The chimeric antibody is produced by continuous perfusion in mammahan cell-culture. The 48kDa F b fragment is purified from cell-culture supernatant. 

Nemati investigated the inhibiting effect of ferrous iron on the rate of oxidation in a bioreactor packed with a polyurethane foam. Fynn and Whitmore investigated the ability of methanogen species to colonize reticulated polyurethane foam in a continuous culture system. Electron micrographs confirmed that two methanogen species colonized the matrix. The methane output was superior to a liquid culture control. 

Ramkrishna et al.m proposed a similar model at about the same time—this too was an unsegregated model which also divided the biomass into two compartments. They referred to the material in the two compartments as G-mass and D-mass, respectively, and suggested that these materials were formed in parallel. They also proposed that the micro-organism produced a toxic substance which inhibited its growth. They produced a set of differential equations obtained from material-balance considerations, to describe the behaviour of such a system in both batch and continuous culture. For batch culture ... 

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