Chemistry: electrical and wave energy – Processes and products – Electrostatic field or electrical discharge
Patent
1993-03-16
1995-04-04
Niebling, John
Chemistry: electrical and wave energy
Processes and products
Electrostatic field or electrical discharge
204149, 20415312, 204403, 204409, 210632, 435817, 435 25, 435 26, 435 27, 435 28, C02F 1461
Patent
active
054034507
DESCRIPTION:
BRIEF SUMMARY
The present invention concerns a method for converting reducible or oxidizable substances in aqueous solution.
Due to the increasing environmental pollution, the supply of pure water is becoming more and more important. In order to use water as drinking water or industrial water it is often necessary to free it of impurities or to determine the amount of impurities in an aqueous solution.
The removal of problematic substances from an aqueous solution can, on the one hand, be achieved by a number of various physicochemical methods. Examples of this are filtration, exchange chromatography and/or reverse osmosis. However, in these methods the problematic substances are not degraded but instead they concentrate in a separate area of the total system. After the separation these substances are then released again into the environment in a high concentration.
The problematic substances can, on the other hand, also be removed by biological methods i.e. by enzymatic degradation in living bacterial cells. However, this degradation in cells is associated with a number of difficulties. Thus problems occur when immobilizing live bacterial cells, the metabolic by-products of bacteria contaminate the purified water. Moreover long reaction periods are necessary in living systems because of the induction times and the large diffusion barriers which the substrate as well as the product have to overcome (e.g. the immobilization matrix and the cell membrane).
Finally the cells may also be attacked and destroyed by the problematic substances.
The object of the present invention was therefore to provide a method of water purification in which the disadvantages of the state of the art are at least partially eliminated.
The object according to the present invention is achieved by a method for converting reducible or oxidizable substances in aqueous solution in which the aqueous solution to be treated is contacted with immobilized oxidoreductases, if desired, in the presence of co-immobilized electron carriers and simultaneously reduction or oxidation equivalents are supplied which are generated by electrolysis of water.
The term "conversion" within the sense of the present invention encompasses a partial removal of reducible or oxidizable substances for water analysis as well as a complete removal for water purification. In this case the essential difference between the determination of substances for water analysis and the complete removal is that from a sample only an amount adequate for the detection of a particular substance is converted.
The use of immobilized enzymes instead of living cells obviates all the aforementioned problems which occur when using living microorganisms for water purification. Furthermore, the problematic substances do not accumulate in a section of the system as in the physicochemical purification method but rather are converted directly into an environmentally compatible form.
In the method according to the present invention the oxidation or reduction equivalents are transferred onto the problematic substances by means of immobilized biocatalysts (enzymes of the oxidoreductase group) and, if desired, additional co-immobilized electron carriers. If the method according to the present invention is used to convert a reducible substance in an aqueous solution then electrons are transferred onto the substance to be removed, if the method according to the present invention is used to convert an oxidizable substance then in contrast electrons are transferred from the substance to be removed onto an oxidizing agent. FIG. 1 shows schematically the course of a reduction using the reduction of nitrate to nitrite as an example. The first partial step of this reaction is the transfer of reduction equivalents (in this case atomic hydrogen produced electrolytically) onto the electron carrier. From there the reduction equivalent is transferred in a second partial step onto the enzyme (nitrate reductase) and from there it is finally transferred onto the substrate (nitrate) which is reduced to nitrite in this manner.
REFERENCES:
patent: 4376689 (1983-03-01), Nakamura et al.
patent: 4464235 (1984-08-01), Simon et al.
patent: 5057421 (1991-10-01), Hofmann et al.
Diekmann Stefan
Mellor Robert B.
Ronnenberg Jorg
Mobitec Molecular Biologische Technologie GmbH
Niebling John
Phasge Arun S,.
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