BIOTECHNOLOGY - V. H. Herasymenko - 2006

Part II. Special Biotechnologies

Chapter 7. BIOTECHNOLOGY OF THE PRODUCTION AND APPLICATION OF IMMOBILIZED PREPARATIONS

7.8. CELL IMMOBILIZATION (ADHESION)

In addition to BIOLOGICALLY ACTIVE SUBSTANCES (including Enzymes), whole microbial Cells can also be immobilized. This phenomenon is known as adhesion.

It should be noted that priority in the field of Cell immobilization belongs not to scientists, but to nature. In nature, most microorganisms exist (at one stage of development or another) in an anchored state on the surfaces of animals, plants, in Water, rocks, and especially in soil. Without adhesion, microorganisms could not exist in nature. It is a vital ecological feature of microbial existence. For instance, in soil, adhesion allows microorganisms to anchor themselves within the soil profile and prevent leaching into lower horizons. Furthermore, adhered cells reside at the solid-liquid interface, where essential nutrients are concentrated. The decomposition of plant residues and certain minerals also occurs exclusively through the adhesion of microorganisms.

The phenomenon of adhesion on various carriers has been utilized for a very long time. Over 150 years ago in Germany, Bacteria immobilized on beech wood shavings were used for vinegar production. In 1857, Louis Pasteur emphasized that The addition of adsorbents stimulates Alcoholic Fermentation.

One of the pioneering works that initiated The Use of intact cells alongside enzymes in the field of enzyme engineering was published in 1970 by Swedish researchers K. Mosbach and P. Larsson. In the Soviet Union, the first works in this direction were published in 1974.

The first industrial process utilizing immobilized cells was implemented in 1973. The renowned Japanese company Tanabe Seiyaku produced aspartic acid from fumaric acid using Escherichia coli cells immobilized in a polyacrylamide gel. Today, there are over a dozen biotechnological processes that employ immobilized cells (for the synthesis of Amino Acids, organic acids, and Antibiotics).

The enzymatic activity of immobilized cells is also applied in wastewater Treatment, particularly for the removal of toxic compounds such as phenol, benzene, and hexamethylenediamine.

Furthermore, the degradation of unnatural substances is possible, such as the cyclic dimer of aminocaproic acid found in wastewater from nylon production. Pilot plants have been developed utilizing a mixture of adsorbed microorganisms for wastewater denitrification, as well as for the extraction of heavy metals. The feasibility of using whole cells of Alcaligenes eutrophus, immobilized in alginate or carrageenan gel, for the removal of tritium from wastewater has been demonstrated. 10 g of cells (wet biomass) are equivalent to 1 g of platinum catalyst.

Immobilized cells are used for treating not only wastewater but also organic waste. A Reactor with adsorbed cells operated under anaerobic conditions for two years. The resulting biogas contained 90% methane and less than 5% CO₂.

Cells in various states can be used for immobilization: living and damaged to varying degrees. Single-step reactions can be carried out by both living and damaged cells. Multi-enzyme reactions are conducted using living cells capable of regenerating ATP and other Coenzymes (NAD, NADP) over extended periods.

Immobilized cells offer certain advantages over immobilized enzymes: the USE OF IMMOBILIZED cells eliminates The Need for expensive extraction and purification of target enzymes; enzymes within The Cell function in their native environment, minimizing Denaturation during operation; cells perform single- and complex multi-stage synthesis processes in virtually a single step; in some cases, they exhibit higher enzymatic activity and stability of individual enzymes; and they provide a significantly wider range of Applications and greater scalability for biotechnological processes.

The main drawbacks of adhesion include: diffusion limitations for both the substrate entering the cell and the reaction product exiting in the reverse direction through The Cell wall, Plasma Membrane, or intracellular membrane; the necessity of maintaining cell integrity and retaining cells in the growth phase where the desired enzymes are synthesized; and the potential for undesirable Side Reactions due to the presence of A wide variety of enzymes within the cell (which can be an advantage in some cases).

However, despite these drawbacks, this branch of biotechnology is highly promising (judging by the number of publications and expert assessments) and will gradually supplant processes utilizing both immobilized enzymes and free cells. The most promising avenues for realizing the biotechnological potential of immobilized cells include cell and Introduction/32.html">Genetic Engineering, hybridoma technology, subcellular engineering, soil biotechnology, etc.

It is worth noting that not only whole microbial cells can be immobilized, but also PLANT AND ANIMAL tissue cells, utilizing them as active biocatalysts for the synthesis of physiologically active substances. The immobilization of cell Organelles as active multi-enzyme systems is also a promising approach.