Bioreactivity

The main reason for the importance of aeration Hes in the limited solubiUty of oxygen in water, a value which decreases in the presence of electrolytes and other solutes and as temperature increases. A typical value for the solubiUty of oxygen (the equiUbrium saturation concentration) in water in the presence of air at atmospheric pressure at 25°C is about 0.008 kg 02/m (= Sparts per million = 0.25 mmol/L). Thus, for a yeast or bacterial bioreaction demanding oxygen at the rates given in Table 1, all oxygen is utilized in about 10 to 40 s (3,7). 

Nielsen, J., and J. ViUadsen, Bioreaction Engineering Fiinciples, Plenum, New York, 1994. 

The gas distribution system can be composed of a network of perforated pipe, slotted or vented concrete block, or metal grating. When there are no space hmitations, single-level filters are used. In regions where footprint space is hmited, hke Japan, multiple-deck filter beds have become commonplace. If inorganic compounds are being treated, corrosion-resistant materials of construc tion are used due to the acidic by-products of the bioreaction. 

Nielsen, J. and Villadsen, J., Bioreaction Engineering Principles . New York Plenum Press, 1994, pp. 229 135. 

The solubilization of enzymes and proteins in water-containing reversed micelles has attracted a great deal of interest for their selective separation, purification, and efficient refolding and for bioreactions involving a wide class of polar, apolar, and amphiphilic reactants and products [13,44,162-164]. 

Lendvay JM et al. (2003) Bioreactive barriers a comparison of bioangentation and biostimnlation for chlorinated solvent remediation. Environ Sci Technol 37 1422-1431. 

Most nonconventional media used for bioreaction consist of more than one distinct phase. The organic phase can be used as nonpolar fluid, which acts as a reservoir for one or many reactants. It is generally a continuous phase. The other phase contains the biocatalyst and is generally the site for the reaction. This relatively polar phase is continuous or dispersed in the organic phase. 

The presence of an organic phase in the bioreaction medium is only useful when the partition coefficient of at least one reactant is significantly greater than the unity. The characteristics of the selected solvent clearly influence the partition coefficients of substrates and products between the two phases. When enzyme is inhibited by high substrate or product concentrations, it is convenient to use solvents with high partition coefficients while the opposite has to be done when enzyme has low affinity with its substrate. Eggers et al. [29] define the overall biphasic concentration referred to the total volume of the system ... 

Modeled rates (curve d. Fig. 5) agreed with those determined experimentally. We suggest that the interaction of mass transfer and metabolism consisting of two or several bioreactions in compartmentalized media is an interesting phenomenon, which has not been fully researched to date. 

Many interesting biocatalytic reactions involve organic components that are poorly water-soluble. When using organic-aqueous biphasic bioreactor, availability of poorly water-soluble reactants to cells and enzymes is improved, and product extraction can be coupled to the bioreaction. Many applications in two-phase media can use the existing standard-type bioreactors, such as stirred-tank, fluidized-bed, and column reactors with minor adjustments. 

As an example of aboveground treatment, a site in Mission Viejo, California had an operating DPE system withdrawing soil vapor and groundwater for treatment with oxidation and bioreaction,... 

Brandenburg A., Krauter R., Kunzel C., Stefan M., Schulte H., Interferometric sensor for detection of surface-bound bioreactions, Appl. Opt. 2000 39 6396-6405. 

Xu P, Quian XM, Wang YX, Xu YB (1996) Modelling for waste water treatment Rhodop-seudomonas palastris Y6 immobilized on fiber in a columnar bioreacter. Appl Microbiol Biotechnol 44 676-682... 

Nielsen J, Villadsen J (2002) Bioreaction engineering principles, 2nd edn. Kluwer Academic/ Plenum Publishers, Dordrecht, Netherlands... 

Below the results of Sensitivity Runs with MADONNA are given from the BIOREACT example that is run as a batch fermenter system. This example involves Monod growth kinetics, as explained in Section 1.4. In this example, the sensitivity of biomass concentration X, substrate concentration S and product concentration to changes in the Monod kinetic parameter, Ks, was investigated. Qualitatively, it can be deduced that the sensitivity of the concentrations to Ks should increase as the concentration of S becomes low at the end of the batch. This is verified by the results in Fig. 2.30. The results in Fig. 2.31 give the sensitivity of biomass concentration X and substrate concentration S to another biological kinetic parameter, the yield coefficient Y, as defined in Section 1.4. 

All three bioreactor modes described above can be simulated using the example BIOREACT. 

Optical biosensors can be designed when a selective and fast bioreaction produces chemical species that can be determined by an optical sensor. Like the electrochemical sensors, enzymatic reactions that produce oxygen, ammonia, hydrogen peroxide, and protons can be utilized to fabricate optical sensors. 

Once a bioremediation effort is started, the bioreactions that occur in the presence of added electron acceptors will result in significant variations of water chemistry across the three-dimensional area of the aquifer. Careful monitoring of these variations is an important indicator of the effectiveness of the remediation process. 

If the pH is adjusted as part of an engineered remediation, the microbial balance may be upset and bioreactions slowed until the microbe cultures adjust to the new conditions. Alternatively, if the release of organic chemicals has altered the pH outside the natural range, it may be necessary to add certain chemicals (i.e., aluminum sulfate, carbon dioxide, sodium hydroxide, etc.) to return the pH to preexisting conditions. Changes of pH should be monitored since rapid changes of more than 1 to 2 pH units over a short period can inhibit microbial activity and may extend the acclimation period before the microbes adapt and renew activity. 

While the above discussion describes testing of aerobic microbial activity, the same scenario is applicable for anaerobic bioreactions. The primary difference is the analytical parameter. The uptake of carbon dioxide, nitrate degradation, sulfate reduction, or iron reduction may be monitored instead of oxygen utilization. 

In this chapter chromatographic bioreactors are considered as chromatographic reactors where the reaction is catalyzed by an enzyme or enzyme system, which can be present in pure form or as a cell component. The enzyme can be immobilized on the matrix or it can be dissolved in a liquid phase. Therefore, the reaction can take place in either phase. Several different bioreactions were performed in chromatographic reactors of different types. In the following part some pertinent examples are presented according to their type of reaction. 

Nitriles differ from all other classes of compounds discussed in Sect. 11.6 in terms of both chemistry and bioreactivity. It is essential, however, to discriminate between aliphatic and aromatic nitriles. 

Well-designed reflectance cells have made this strong absorber of water useful in the process vat. Using long path-length gas cells also allows the analyst to monitor head-space gases in order to follow bioreactions. 

A relatively short but interesting paper by Arnold et al.55 suggests different calibrations for different segments of a bioreaction. Using the cultivation of S. fradiae and monitoring the oils and tylosin, the reaction was followed for 150 h. It was determined that the extensive matrix changes over the entire reaction time would make calibration difficult. The process was broken into (1) 0 to 50 h, (2) 50 to 100 h, and (3) 100+ h. 

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