Batch reactors bioreactors

Recent reports on other forms of reactors are also available. Immobilized cell bioreactors, upflow sludge blanket reactors, draft-tube airlift reactor and other have been suggested. Each of these reactors has its own pros and cons and the advantages need to be evaluated with the whole process in mind. Further work is necessary in this area. Several process schemes have been considered and evaluated with the batch reactor design as the core BDS reactor ... 

Transient Holdup Profiles in an Agitated Extractor 459 Homogeneous Free-Radical Polymerisation 310 Batch Reactor Hydrolysis of Acetic Anhydride 247 Continuous Bioreactor with Inhibitory Substrate 543 Dynamic Oxygen Electrode 462... 

Although the yields and total growth rate are useful parameters, it is the state variables like the concentrations of biomass, substrate and product, and the culture parameters like the specific rates of growth, substrate uptake, etc., that provide a complete description of the bioreactor. One attempt in estimating these variables from R and the yields consisted of integrating the governing differential equation with known initial conditions and the measured values for R and the yields (9). For a batch reactor, for example, b was estimated by integrating... 

The above approach, however, does not give any consideration to random errors and noises which are always present both in the process and in the measurements and which corrupt the obtained values of R and the yields. In fact, it can be shown (10) that the variance of the state estimates obtained this way increases continuously with time if a batch reactor is employed. Similar results can be obtained for a fed-batch reactor and the conclusion reached earlier (9), relating the need for reinitialization of the state estimate after several integration steps of Eq. (5) can be considered as a manifestation of the above assertion. For a continuous bioreactor, the variance tends to a constant but very high value, and still large measurement errors tend to produce large estimation errors. 

Most commercial bioreactions are carried out in batch reactors. The design of a continuous bioreactor is desired since it may prove to be more economically rewarding than batch processes. Most desirable is a reactor that can sustain cells that are suspended in the reactor while growth medium is fed in, without allowing the cells to exit the reactor. Focus mixing modeling, separations, bioprocess kinetics, reactor design. 

Biochemical reactions such as aerobic and anaerobic fermentations occur in the presence of living organisms or cells, such as bacteria, algae, and yeast. These reactions can be considered as biocatalyzed by the organism. Thus in a typical bioreactor a substrate (such as glucose) is fed into the fermenter or bioreactor in the presence of an initial amount of cells. The desired product can be the cells themselves or a secreted chemical called a. metabolite. In either case the cells multiply in the presence of the substrate, and the rate of production of cells is proportional to the concentration of the cells— hence this process is autocatalytic. In a batch reactor with ample... 

FIGURE 26.3 (See color insert following page 40). Modes of bioreactor operation. (A) Batch bioreactor, (B) fed-batch reactor, and (C) perfusion bioreactor. 

Fed-batch bioreactors—This method begins as a batch mode of operation as cells undergo their initial growth phase. However, run time, cell mass, and product titer are increased with the addition of supplemental nutrients, or feeds, to the bioreactor. These reactors are cost effective to run because higher product titers can be achieved from a single extended reactor run, increasing volumetric productivity. However, volumetric output is fundamentally restricted by the size of the vessel, and formation of toxic cellular metabolites can limit the duration of each reactor run. 

Lactic acid is an important additive and preservative agent in the chemical, cosmetics, pharmaceutical, and food industries. It is also used as the base for the production of biodegradable polymers like polylactates [4.12]. Its current worldwide production is estimated to be 40,000 tons per year. The results reported by Olmos-Dichara and coworkers [4.13] are typical of the results reported in many of the prior studies of this reaction system. They carried out a study comparing the performance of a batch reactor and a MBR for the production of lactic acid using L. cassei sp. rhamnosus as a biocatalyst. The MBR consists of the batch bioreactor coupled with a cross-flow mineral membrane filtration unit. MBR productivity was eight times that of the batch reactor, while the biomass concentration (77g f ) in the MBR was 19 times that found in the batch culture. 

Membrane bioreactors have been modelled using approaches that have proven successful in the more conventional catalytic membrane reactor applications. The simplest membrane bioreactor system, as noted in Chapter 4, consists of two separate units, a bioreactor (typically a well-stirred batch reactor) coupled with an external hollow fiber or tubular or flat membrane module. These reactors have been modelled by coupling the classical equations of stirred tank reactors with the mathematical expressions describing membrane permeation. What makes this type of modelling unique is the complexity of the mecha-... 

In developing the solution to Illustration 13.1, we utilized a variation of the traditional material balance on a batch reactor that is often useful in the analysis of biochemical transformations carried out in batch and semibatch modes of operation. In particular, we took into account variations in the volume of the broth in the bioreactor by first converting concentrations of biomass and substrate into the total quantities of these materials present in the bioreactor. In so doing we were implicitly recognizing that the proper form of a material balance on species i for variable-volume situations is... 

Consider the task of ascertaining the time variation of the total masses of both substrate and microorganisms for a fermentation that takes place in a laboratory-scale batch reactor with a working volume of 1L. Initially, the bioreactor contains 20.17 g of glucose and 6.00 g (dry weight) of an unspecified microorganism. The values of the biomass specific growth rate (iVax) substrate... 

Relative to stricfly batch bioreactors, continuous and fed batch bioreactors require more connections to process stteams through which sterility must be maintained throughout the entire period the reactor is onstream. When contamination does occur in equipment used to carry out a continuous process, it can rapidly spread to downstream units. By contrast, confinement or isolation of contaminants can be accomplished more readily in a batch reactor and its associated auxiliary facilities. 

Operation in a perfusion mode can be viewed as a form of recycle of biomass that permits one to substantially increase the amount of biomass in the bioreactor. In a batch reactor used for cultivation of mammalian cells, the maximum cell concentration is roughly 1 million cells/mL. By... 

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