Biological immobilization

The biological immobilization is a conversion of mineral nitrogen, in which it is bound into organic structures. It occurs as a result of the assimilation of mineral nitrogen by plants and by the rich microflora. The immobilization by plants is the most important form of nitrogen immobilization. 

Mineral nitrogen in any form accepted by plants cannot be directly incorporated into proteins, however, it needs first to be transformed via keto acids into molecules of amino acids. All these processes are anabolic and endothermic and thus, they require energy, which is mainly released by the oxidation of organic substances produced during photosynthesis and CO2 assimilation. 

The reduction of nitrates to nitrites and ammonia occurs just after their entrance into plants, mainly in thin small roots. When the roots do not contain sufficient amounts of reducing substances, then the enzyme nitrate reductase is unable to reduce all the nitrogen accepted. It is then transported into aboveground organs of plants, where its reduction can continue. In the case of an uptake of excess nitrates only 30 to 50% is reduced in the roots and the remaining portion is transported into the stem and leaves. They can accumulate, polluting the plant mass if there is insufficient energy for the reduction. 

The basic requirement for nitrogen immobilization by microorganisms is the presence and biological decomposition of organic matter with a low nitrogen content or with a high C N ratio. Under these conditions, the mi- 

At the present time, particularly in developed countries, the nitrogen supply to the soil is at a high level, so that even ploughing of all the straw into the soil need not result in any major decrease in the content of mineral nitrogen in the soil. 

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Although the knowledge of the sample surface area is important, as already pointed out, the pore size distribution is even more critical, since it greatly affects the activity-coupling yield of the biologic immobilization because of the diffusion-controlled phenomena. 

If not grazed, or if the pasture is not burned, most of the P absorbed in plant tops will be immobilized by plant tissue and, thus, will be unavailable in the soil. Transfer of P and N by nutrient resorption in forage plants and in the weedy vegetation prior to leaf fall induces low nutrient concentration in litter (Table 6.6) and may in part explain the decreasing amount of available soil P often associated with an increase in the weed biomass of a degrading pasture or with pasture age. Without this biological immobilization, however, these nutrients would be more vulnerable to loss through runoff and erosion. 

Immobilization may take place as part of the actual formation of the sensor active surface, or may be done after a base layer is established on the transducer. For example, entrapment and cross-linking immobilization methods involve the mixture of active component with carriers and polymerizing agent(s) and application of the mixture directly to the transducer to form the active surface. Covalent, adsorption, and biological immobilization methods attach the active component to a previously prepared surface, such as activated silica. 

Table 8.6 Examples of sensors using biological immobilization methods. 

Types of modifications and their popularity (compared again via a percentage estimated from the respective original articles and based on approximate summaries in [3, 5, 85]) manual bulk modification, 40% chemical or biological immobilization, 20% in situ modification (in sample solutions), 20% other approaches, 10%. 

One chromium-cleansing enzyme is proactive,. .. K. J. Robins et al. Escherichia coli NemA is an efficient chromate reductase that can be biologically Immobilized to provide a cell free system for remediation of hexavalent chromium. 2013. PLoS One 8(3), p. e59200. DOl 10.1371/journal.pone.0059200. 

Fiber-optic chemical sensors can be divided into two categories based on their structure (a) Intrinsic sensors are based on the analyte s intrinsic optical properties, and (b) extrinsic sensors are based on sensing materials (chemical or biological) immobilized to the fiber surface, with... 

Wagner P 1998 Immobilization strategies for biological scanning probe microscopy FEBS Lett. 430 112... 

Potcntiomctric Biosensors Potentiometric electrodes for the analysis of molecules of biochemical importance can be constructed in a fashion similar to that used for gas-sensing electrodes. The most common class of potentiometric biosensors are the so-called enzyme electrodes, in which an enzyme is trapped or immobilized at the surface of an ion-selective electrode. Reaction of the analyte with the enzyme produces a product whose concentration is monitored by the ion-selective electrode. Potentiometric biosensors have also been designed around other biologically active species, including antibodies, bacterial particles, tissue, and hormone receptors. 

Can the contaminant be brought to a reactor or constmcted wetland where biological systems, microbial or plant, can extract and immobilize the contaminant ... 

Selectivity is an important consideration in analytical chemistry. Biologically derived polymers can be used as highly selective immobilized reagents in analytical appHcations. The first reported use of immobilized biopolymers as biosensors (qv) for the detection of an analyte was made in 1962 (48). Since that first reported use there has been a great deal of development and appHcation of immobilized biopolymers in analytical chemistry. 

In the early years of the chemical industry, use of biological agents centered on fermentation (qv) techniques for the production of food products, eg, vinegar (qv), cheeses (see Milk and milk products), beer (qv), and of simple organic compounds such as acetone (qv), ethanol (qv), and the butyl alcohols (qv). By the middle of the twentieth century, most simple organic chemicals were produced synthetically. Fermentation was used for food products and for more complex substances such as pharmaceuticals (qv) (see also Antibiotics). Moreover, supports were developed to immobilize enzymes for use in industrial processes such as the hydrolysis of starch (qv) (see Enzyme applications). 

Immobilization. Enzymes, as individual water-soluble molecules, are generally efficient catalysts. In biological systems they are predorninandy intracellular or associated with cell membranes, ie, in a type of immobilized state. This enables them to perform their activity in a specific environment, be stored and protected in stable form, take part in multi-enzyme reactions, acquire cofactors, etc. Unfortunately, this optimization of enzyme use and performance in nature may not be directiy transferable to the laboratory. 

There are numerous examples of successful application of the developed procedures using native and immobilized enzymes in analysis of environmental (waters and soils of different types, air) and biological (blood semm, urine) samples. 

The general purpose of ultimate disposal of hazardous wastes is to prevent the contamination of susceptible environments. Surface water runoff, ground water leaching, atmospheric volatilization, and biological accumulation are processes that should be avoided during the active life of the hazardous waste. As a rule, the more persistent a hazardous waste is (i.e., the greater its resistance to breakdown), the greater the need to isolate it from the environment. If the substance cannot be neutralized by chemical treatment or incineration and still maintains its hazardous qualities, the only alternative is usually to immobilize and bury it in a secure chemical burial site. 

The porosity and permeability of CP are the most important factors determining their ability to sorb and immobilize BAS. For solving these problems, it was necessary to synthesize various types of porous and permeable CP differing in the mobility of elements of the crosslinked structure and in the rigidity of the polymer backbone. For biological problems related to the application of CP as biosorbents, it has been found necessary to use CP with a marked structural inhomogeneity. 

All the existing methods of immobilization involve formation of a high local BAS concentration and retention of its biological activity. In this respect, the use of disperse forms of CP as carriers of BAS used for different purposes is very promising [88]. In this case, the CP-protein interaction is an important factor in controlling the structure and properties of these systems. 

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