June 02, 2020

Immobilized cell technology

Immobilized cell technology uses physical or chemical means to immobilize or position cells in a free state in a defined spatial region and maintain their inherent catalytic activity.

Advances in research on immobilized cell technology

First, the characteristics of immobilized cell technology

Immobilized biological cells can continue to proliferate, dormant and decline, and their activity is always stable. In addition to maintaining its original recognition, binding and catalytic activity, immobilized biological cells also have the characteristics of high cell density, fast reaction rate, strong toxic tolerance, high stability, easy product separation, and continuous operation. Greatly increase production capacity.

Second, cell immobilization method

There are many cell immobilization methods. Karel et al. classify them into surface adsorption, multi-media embedding, isolation and self-aggregation. Wang Jianlong divides the currently used immobilization methods into adsorption, embedding, and glue-bonding methods. And interception method; Yang Wenying introduced seven common methods such as adsorption, embedding, covalent bonding, glue-bonding, porous material enveloping, ultrafiltration, and various immobilization methods; According to the presence or absence of external loading, the cell immobilization method is divided into two types: carrier immobilization method and carrierless immobilization method; Zhang Lei et al. divide it into adsorption method, embedding method and covalent according to the different immobilized carriers and methods. Combination method and glue method.

The definitions, advantages and disadvantages of adsorption, embedding, covalent bonding and gel-bonding methods are shown in Table 1.

Table 1 Comparison of various immobilization methods









Also known as the carrier binding method. According to the static electricity, surface tension and adhesion between the charged cells and the carrier, the cells are fixed on the surface and inside of the carrier to form a biofilm.

Physical adsorption method and ion adsorption method

Easy to operate, low activity loss

The force between the cell and the carrier is small and easy to fall off




Embed the cells in the tiny space of the gel or in the ultrafiltration membrane of the semipermeable membrane polymer

Gel embedding method: embedding cells in micropores inside various gels; semi-permeable membrane embedding method: embedding cells in small spheres made of various high molecular polymers

Simple, mild conditions, good stability, high cell capacity

Covalent bonding

The cell surface functional group forms a chemical covalent bond with the reactive group on the surface of the solid support to form an immobilized cell.

The cells are tightly bound to the carrier and are not easy to fall off

Preparation is difficult, and cell activity loss is large




Bifunctional or multifunctional reagents react directly with reactive groups on the cell surface to bond each other into a network structure for cell fixation

Cells are tightly bound to the carrier

Trouble in preparation, large loss of cell activity

Third, the cell immobilization carrier

The carriers suitable for the immobilization technology include organic carriers, polymer carriers, inorganic carriers, etc., and the polymer carrier materials are preferred carrier materials because of their many good properties. Polymer carriers are generally divided into two categories: natural polymer materials and synthetic polymer materials. The natural polymer material carrier includes: carrageenan, gelatin, agar, chitin, chitosan, calcium alginate, cellulose acetate, fibrin, etc.; synthetic polymer materials include: polyamine resin (PAM), polyethylene High polymer such as alcohol (PVA), polyurethane, photosensitive resin, polyethylene oxide.

When selecting a polymer material carrier, the following key factors should be considered; 1) stability of the carrier material (including stability to ambient temperature, pH, microbial reagents and chemical reagents) and compatibility with cells; 2) preparation Methods of immobilization of cells and ease of formation; 3) better mechanical strength and long-term re-use; 4) toxicity (including effects on any cell viability); 5) source and cost of the medium. At present, the search and development of low cost, high efficiency, good permeability, stable performance, safe and non-toxic carrier and simple and easy immobilization method has always been a major direction in the development of immobilization technology.

Fourth, cell immobilization reactor

The productivity of the immobilized cell system and the feasibility of industrial application depend to a large extent on the choice of reactor. The cell-immobilized reactors can be classified into two categories according to their use: 1) a bioconversion reactor whose biological growth is independent of product synthesis; 2) a reactor for producing a primary product. Factors affecting reactor selection include: immobilization methods, shape of immobilized cells, particle size, density, mechanical strength, properties of substrates, inhibition, mechanical properties of fluids, and economic factors. At present, there are five types of reactors to be selected: 1) a continuous agitating reactor suitable for systems with substrate inhibition; 2) a packed bed reactor, also known as a plug flow reactor, which has good product inhibition. The effect is suitable for reactions with longer residence time; 3) fluidized bed reactor, which can be used to treat highly viscous and particulate-bearing substrates, and also for reactions requiring oxygen and exhaust gases; 4) membrane reactor It is suitable for reactions requiring oxygen supply or CO 2 gas emission, but it is not suitable for the reaction of fast cell growth, high cell concentration and easy to cause membrane rupture; 5) Rotary reactor, which has the advantage of easy supply of oxygen, cells The concentration is high, the viscosity of the fermentation broth is low, the energy required is low, and the operating cost is low.

In addition, there are tower reactors, fiber-fixed cell reactors, sieve plate reactors, and circulating bed reactors, but so far there is no universal, ideal reactor, so it is necessary to Product, selection or development of a suitable bioreactor.

Since the membrane-immobilized cell reactor can fix high-density cells in the space formed by the membrane, the cells are in a free environment and protected from shear damage, and the products can be separated in situ to eliminate the inhibitory effect and facilitate Large-scale continuous production, thus greatly improving production efficiency, has been successfully applied to microbial fermentation and large-scale cultivation of animal and plant cells.

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