Cell, immobilization

As in the case of enzymes, whole cells can be immobilized for several advantages over traditional cultivation techniques. By immobilizing the cells, process design can be simplified since cells attached to large particles or on surfaces are easily separated from product stream. This ensures continuous fermenter operation without the danger of cell washout. Immobilization can also provide conditions conducive to cell differentiation and cell-to-cell communication, thereby encouraging production of high yields of secondary metabolites. Immobilization can protect cells and thereby decrease problems related to shear forces. 

Attachment to a Surface wood chips, collagen, microcarriers, ion exchange resins, metal oxides 

Entrapment within Porous Matrices Cordierite, pore glass, acrylamide, alginate, collagen, K-carrageenan 

Containment behind a Barrier polylysine, ethylcellulose, emulsion, synthetic membrane 

Self-aggregation mycelial pellets, microbial floes, polyelectrolytes, cross-linking agents 

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These reactors contain suspended solid particles. A discontinuous gas phase is sparged into the reactor. Coal liquefaction is an example where the solid is consumed by the reaction. The three phases are hydrogen, a hydrocarbon-solvent/ product mixture, and solid coal. Microbial cells immobilized on a particulate substrate are an example of a three-phase system where the slurried phase is catalytic. The liquid phase is water that contains the organic substrate. The gas phase supplies oxygen and removes carbon dioxide. The solid phase consists of microbial cells grown on the surface of a nonconsumable solid such as activated carbon. 

D-Pantolactone and L-pantolactone are used as chiral intermediates in chemical synthesis, whereas pantoic acid is used as a vitamin B2 complex. All can be obtained from racemic mixtures by consecutive enzymatic hydrolysis and extraction. Subsequently, the desired hydrolysed enantiomer is lactonized, extracted and crystallized (Figure 4.6). The nondesired enantiomer is reracemized and recycled into the plug-flow reactor [33,34]. Herewith, a conversion of 90-95% is reached, meaning that the resolution of racemic mixtures is an alternative to a possible chiral synthesis. The applied y-lactonase from Fusarium oxysporum in the form of resting whole cells immobilized in calcium alginate beads retains more than 90% of its initial activity even after 180 days of continuous use. The biotransformation yielding D-pantolactone in a fixed-bed reactor skips several steps here that are necessary in the chemical resolution. Hence, the illustrated process carried out by Fuji Chemical Industries Co., Ltd is an elegant way for resolution of racemic mixtures. 

Corynebacterium glutamicum (CGMCC No. 1464) cells immobilized in calcium alginate beads cross-linked with polyethenimine and glutaraldehyde have been employed for the production of nicotinamide from 3-cyanopyridine [21], The reaction was mn at 10-15 °C,... 

A thermally stable NHase from Comamonas testosteroni 5-MGAM-4D (ATCC 55 744) [22] was recombinantly expressed in Escherichia coli, and the resulting transformant cells immobilized in alginate beads that were subsequently chemically cross-linked with glutaraldehyde and polyethylenimine. This immobilized cell catalyst (at 0.5 % dew per reaction volume) was added to an aqueous reaction mixture containing 32wt% 3-cyanopyridine at 25 °C, and a quantitative conversion to nicotinamide was obtained. The versatility of this catalyst system was further illustrated by a systematic study of substrates, which included... 

Bejar, P., Casas, C., Godia, F., and Sola, C., The Influence of Physical Properties on the Operation of a Three Phase Fluidized-Bed Fermenter with Yeast Cells Immobilized in Ca-Alginate, App. Biochem. Biotechnol., 34/35 (1992)... 

Wu, K. Y. A., and Wisecarver, K. D., Biological Phenol Degradation in a Countercurrent Three-Phase Fluidized Bed Using a Novel Cell Immobilization Technique, AIChE Symp. Series, 86(276) 113 (1989)... 

Sakurai K, Teramura Y, Iwata H (2011) Cells immobilized on patterns printed in DNA by an inkjet printer. Biomaterials 32 3596-3602... 

G. Carturan, R.D. Monte, G. Pressi, S. Secondin, and P. Verza, Production of valuable drugs from plant cells immobilized by hybrid sol-gel Si02. J. Sol-Gel. Sci. Technol. 13, 273—276 (1998). 

On the other hand, cell immobilization on carriers definitively improves bioreactor efficiency. Cell aggregation in a biofilm structure increases process stability and tolerance to shock loadings. A proper selection of operating conditions allows... 

Whole cell immobilization was defined by Karel et al. [35] as, the physical confinement or localization of intact cells to a certain region of space with preservation of some desired catalytic activity or by Anderson [36] as, there is a physical confinement or localization of microorganisms that permits their economic... 

Cell immobilized cultures of Phanerochaete chrysosporium and repeated-batch decolorization were reported by Yang and Yu [46]. Diazo-dye Red 533 was decolorized by PuF immobilized culture, and decolorization efficiency of 80% or higher was achieved within a period of 1 or 2 days. 

Norton S, D Amore T (1994) Physiological effects of yeast cell immobilization applications for brewing. Enzyme Microb Technol 16 365-375... 

Cells immobilized in gels showed lower volumetric rates of hydrogen photoproduction as compared with immobilization on porous glass. In some cases, the diflusion limitation of the process rate was the main reason as shown above. In other cases thick layer of dense culture was insufficiently illuminated. The observation, that hydrogen production rate was higher when the layer of matrix was thinner, supports this suggestion (Tab. 3). 

Enzymes can be immobilized by matrix entrapment, by microencapsulation, by physical or ionic adsorption, by covalent binding to organic or inorganic polymer-carriers, or by whole cell immobilization (5 ). Particularly impressive is the great number of chemical reactions developed for the covalent binding of enzymes to inorganic carriers such as glass, to natural polymers such as cellulose or Sepharose, and to synthetic polymers such as nylon, polyacrylamide, and other vinyl polymers and... 

Mobed M, Nishiya T, Chang TM. Purification and characterization of liposomes encapsulating hemoglobin as potential blood substitutes. Biomater Artif Cells Immobil Biotechnol 1992 20 53. 

K. F. Gu and T. M. S. Chang, Production of essential L-branched-chain amino acids in bioreactors containing artificial cells immobilized multienzyme systems and dextran-NAD+, Biotechnol. Bioeng., 36, 263-269 (1990). 

The first experiments describing the clonal growth of hemopoietic progenitor cells immobilized in a soft gel matrix in vitro were reported by Bradley and Metcalf (1966) and Pluznick and Sachs (1965). Clonogenic cells are plated in the presence of various of feeder cells, medium conditioned by the growth of different tissues or cell lines in cultures (for example, 5637 bladder carcinoma conditioned media) and colony stimulating factors such as GM-CSF, G-CSF, M-CSF, Epo, interleukins. 

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