Cell immobilization membrane

This chapter focuses on two types of biocatalyst membrane reactors, namely, enzymatic membrane reactors and cell-immobilized membrane reactors. The fundamental characteristic of an enzymatic membrane reactor is the separation of enzymes (biopolymers) from products and/or substrates by a semipermeable membrane (Jochems et al, 2011 Lopez et al, 2002). Permeable substrates and products can be selectively separated from the reaction mixture by the action of a driving force across the membrane (chemical potential, pressure, electric field) that causes the movement (diffusion, convection, electrophoretic migration) of solutes. In an enzymatic membrane reactor, the biocatalyst (enzyme) is retained within the system by... 

In a cell-immobilized membrane reactor, the membrane plays the role of a separator of two liquid streams, namely, the wastewater and the cell medium, and simultaneously acts as a support for biofilm growth (Chung et al., 2004 Juang et al., 2008 Li and Loh, 2007a) (Fig. 20.2). The wastewater is passed through the lumen side of the hollow-fiber membrane module and the nutrient-enriched cell medium flows across the shell side. In this way, the microbes can treat the effluent on one side and can be kept active via the nutrient stream at the other side without contamination of the effluent by the nutrient. 

Table 20.3 Removal of xenobiotics by cell-immobilized membrane reactors... 

Based on the list of literature reviewed in this chapter, it can be pointed out that a comparatively limited number of studies on cell-immobilized membrane reactors (Table 20.3) and extractive membrane bioreactors (Table 20.8) have been conducted. Studies only from certain research groups who targeted a limited number of recalcitrant compounds (predominantly phenol) are available. Currently only a few publications on these topics are published each year. This obviously is an impediment to progress in their scale-up. Major hurdles for a commercial realization of EMBRs are the cost of silicone rubber membranes and other difficulties associated with the scaling up process. The development and implementation of these systems at an industrial scale requires a broader as well as in-depth understanding of the core processes. 

It is expected that the technology of enzyme- and cell-immobilized membranes in which the reaction and separation are performed simultaneously can be applied to a wide variety of fields which were previously impossible. In the future, this technology will be expanded to other fields. To achieve this objective, a joint research project is very important,because the science and technology of enzyme- and cell-immobilized separation membranes is a landmark in the academic, industrial and medical fields. 

Tuerker and Mavituna immobilized Trichoderma reesei within the open porous networks of reticulated polyurethane foam matrices. Growth pattern, glucose consumption, and cellulase production were compared with those of freely suspended cells. The method of immobilization was simple and had no detrimental effect on cell activity. Hundreds of similar projects could be cited. Not all rated the use of polymethane as the preferred technique. If a statistical analysis were conducted on aU the immobilization literature, we are sure that no single technique would be dominant. However, the combination of ease of immobilization, cost of materials, flow-through properties, control of flux rate through the immobilizing membrane, high surface-to-volume ratio, and other factors make polymethane a viable substratum for the continuous production of proteins. 

If sufficient nutrients (e.g., 0.3 g l 1 glucose) are present in a sample solution, a constant current is obtained from the electrode. The current depends on the total respiration activity of immobilized cells. Therefore, the total respiration activity of bacteria, the current, depends on the number of viable cells immobilized onto the acetylcellulose membrane. The relationship between the current and the cell numbers on the acetylcellulose... 

Drug delivery, dialysis membranes, polyelectrolyte complexes for cell encapsulation, and cell immobilization Complexes for cell encapsulation... 

Enzymes or whole cells can be immobilized in ultrafiltration (UF) and reverse osmosis (RO) membranes by several methods. First, cellulose acetate or polysulfone are used to obtain asymmetric membranes by the phase Inversion technique. Albumin and glutaraldehyde are then used for cell Immobilization within the membranes via co-cross-llnklng methods (25,26). 

Pseudomonas aminovirans cells immobilized onto a nylon membrane and attached to a polypropylene-coated oxygen electrode Trimethylamine [44]... 

The large-scale culture of tobacco cells, claimed to contain 5-30% nicotine, for the preparation of a tobacco-smoking substitute have been patented (see Table XI). Hallsby and Shuler (260) reported the growth of tobacco cells immobilized in a membrane-type reactor using different flow patterns. 

Canaries are no longer used in modern mines, but living cells immobilized on a semiconductor chip could serve the same purpose. It has been found that as the cell dies, there is a short increase in electrical resistance of its membrane. Presence of toxic gases can be detected by this type of biosensor. The challenge now is to keep the cell alive for a long time in storage until the biosensor can be used as a detector of toxins. 

Wong, H., Chang, T.M.S. The microencapsulation of cells within alginate poly-L-lysine microeapsules prepared with the standard single step drop technique Histologically identified membrane imperfections and the associated graft rejection. Biomater. Artif. Cells Immobil. Biotechnol. 1991, 19 (4), 675-686. 

Cell immobilization on a solid carrier can be done by physical adsorption due to electrostatic forces or by covalent binding between the cell membrane and the carrier. Immobilization can also be done by growth of the cells into natural cavities on a surface, and therefore, containment of the cells due to entrapment and/or a combination with electrostatic and other weak forces (Figure 43.2). The strength with which the cells are bonded to the carrier as well as the depth of the biofilm varies... 

Cell immobilization via a combination of ionotropic gelation and polyelectrolyte complex formation (e.g., with chitosan) in drug delivery systems and dialysis membranes... 

---