Bioreactor dimensioning

Eq. 5.24 represents the model of steady-state operation of CSTR. As in the case of CPBR, it allows the determination of the steady-state X for any given combination of Mcat/F and can also be used for bioreactor design, since bioreactor dimensions will be determined from the concentration of biocatalyst that can be adequately handled in the bioreactor ... 

The main part of the report describes the results of systematic investigations into the hydrodynamic stress on particles in stirred tanks, reactors with dominating boundary-layer flow, shake flasks, viscosimeters, bubble columns and gas-operated loop reactors. These results for model and biological particle systems permit fundamental conclusions on particle stress and the dimensions and selection of suitable bioreactors according to the criterion of particle stress. 

Two photo-bioreactors, A and B, of flat-rectangular shape were compared for the hydrogen production and P-D-HB accumulation in the culture broth during photo-incubation of Rb. sphaeroides KD131 Hup/Phb mutant strain. Both of them had the same dimension, 20... 

Yabannavar et al. [81] used Eqs. (19) and (20) for scale-up purposes. Based on successful operation conditions determined for an existing 12-L bioreactor, they calculated the spin-filter dimensions and operation conditions for an existing 175-L bioreactor. Experiments with the spin-filter designed for the large-scale bioreactor resulted in an absence of filter clogging with cell retention efficiency similar to the 12-L bioreactor. This was considered as an evidence that the suggested scale-up strategy is adequate. 

Flow dynamics predict that flow through a pipe is nonuniform with regard to velocity across the diameter of a pipe, for instance. The flow at pipe walls is assumed to be zero. In our idealized biochemical reactor, this concept is represented by a boundary layer in contact with the biofilm. It does not have, of course, a discrete dimension. Rather, it is represented as an area in the structure that has reduced flow and therefore different kinetics than what we would assume exist in a bulk liquid. The boundary layer is affected by turbulence and temperature and this is unavoidable to a degree. Diffusion within the boundary layers is controlled by the chemical potential difference based on concennation. Thus the rate of transfer of pollutant to the organisms is controlled by at least two physical chemical principles, and these principles differentiate an attached growth bioreactor from a suspended growth bioreactor. 

The fermentation tests were carried out in shake flasks, STR and FBR. The effect of the following parameters was investigated the amount of gel and the total cell concentration in the bioreactor the addition of hydrogen acceptor (acetone), instead of air, to activate the electron transport in the respiratory chain and the use of Teflon-made filters as air diffusers to reduce air bubble dimension and increase oxygen solubility. 

However, scale-up of this type of system is limited due to the fact that oxygen transfer is a function of the area of the wave-containing liquid surface. Since the area increases with the square and the volume with the third power of a linear dimension, it is expected that this technology will reach a scale limit. Nevertheless, the companies that market this type of bioreactor offer bioreactors up to at least 500 L working volume (Wave Biotech, 2006). 

Bioreactors must fulfill a twofold purpose in bioprocessing—industrial production and process kinetic analysis. A standard research bioreactor has been recommended by the European Federation of Biotechnology (Dechema Monograph, 1982) It is a stirred tank in which all dimensions are standardized (cf. Table 3.7). 

The steps between the cell bank and the production fermentation serve the purpose of expanding the seed volume (biomass) to finally provide sufficient cells to inoculate the main fermenter. Early seed stages, also referred to as precultures, are often run in shake flasks or in T-flasks and roller bottles in the case of cell culture, whereas subsequent stages are performed in stainless steel or single-use bioreactors. The dimensions of the seed bioreactors are adjusted to the biological system, as shown in Table 1.5. 

The hollow-fiber membrane bioreactor took the simple cylindrical geometry housing [dimension 13 mm inner diameter (ID) x 22 mm outer diameter (OD) x 40 mm L see Fig. 14.2]. Cellulose acetate hollow-fiber membranes [200 p,m ID, wall thickness of 14 p,m and molecular weight cutoff (MWCO) of 10 kDa] derived from hemodialysers used to construct the HFMBs. The hollow-fiber membranes were fixed in the bioreactor by using molded silicon rubber. The effective length of the fiber in the reactor was 30 mm with approximately 200 fibers in each bioreactor. The distance between adjacent fibers was approximately 400 p-m, of the order of the distance between natural blood capillaries in human bone. The volume external to the hollow fibers in each HFMB was approximately 3.5 mL, and this volume was available for the collagen gel together with the microcarriers with adherent cells. 

---