2-Deoxy-D-glucose i bekæmpelsesmidler til byggematerialer

English summary

PART 1

The traditional products for industrial preservation of wood contain metals, for example water-dissolved products containing copper, chrome and phosphorus are currently used in Denmark. In most countries compounds with copper, chrome and phosphorus are still used. Some compounds used for vakuum treatment contain organotin compounds dissolved in organic solvents. Some of these compounds can also be found in products used for remedial treatment and surface treatment in situ. These compounds are being sold and used both by private individuals and professionals to prevent and to combat fungus attacks. Besides these compounds there are also boron diffusion products, which have gained a floting in the remedial treatment market. Both the industry, the buyers and the environmental authorities demand that the products being used do not put the environment at risk. Therefore all wood and masonry treatments, which are being imported, produced, sold and used in Denmark, have to be approved by The Danish Environmental Protection Agency. An extended effort is being made in certain parts of the treatment industry in order to develop products less harmful and in the latest years preservation compounds with both phosphorus as chrome have been prohibited in Denmark. There is now focus on terpentinedissolved products and compounds containing boron.

During the last couple of years, The Department of Biotechnology has applied itself to the development and the testing of new preservatives based on the exact knowledge of the biology of the fungal wood decay as well as of the chernical and enzymatic reactions, which determine the ability of the fungus to decay wood.

In connection with an earlier project called »The fungus package«, financed by The National Housing and Building Agency, three Danish credit associations (WP Kredit A/S, KD, Nykredit), Danish insurance companies and Grundejernes Investeringsfond (danish investment fund), an enzyme-inhibitor-based concept for wood preservation treatment was developed. Laboratory tests have shown that the agent has a marked effect on wood decaying fungi, and that is why this agent could be applied as a wood preservation agent. The agent is 2-Deoxy-D-glucose, also known as 2-DOG.

In the present preliminary project tests have been perforrned partly on 2-DOG and partly of a cognate agent, glucosamine.

2-DOG is very efficient in its protection against fungi generating brown rot, but a somewhat higher concentration is required in order to hinder the fungi generating white rot. The most common and rnost serious wood decaying fungi generate brown rot, i. e. these fungi primarily decay the wood cellulose. Some other fungi decay the cellulose and the lignin at the same time, thereby creating the white rot. These fungi are primarily found in exterior woodwork.

The decay of the fungi on wood is a combination of an enzymatic reaction and a chemical reaction (Fenton reaction) which involves iron. This can be complex binded with EDTA and polyphosphate. Thus the decay of wood is hampered on both brown rot and white rot fungi.

That is the reason why we have examined the possibility of obtaining an effect and possibly a synergistic effect by the preservation of wood using complex binding agents, alone or in combination with 2-DOG. Both EDTA and Polyphosphate intensifies the effect that 2-DOG has on both brown rot and white rot fungi.

Chitosamine (glucosamine), which ostensibly should have an effect similar to that of 2-DOG, has been tested. These tests has shown, that glucosamine do not hinder the wood decaying fungi - if anything the opposite. There are indications that the fungi can use the glucosamine as a nutrient, for instance in connection with the synthesis of chitin, which form part of the fungi cell walls.

2-DOG is easily soluble in water, and it is therefore also easily leached from the wood after the preservation process. Before this agent will be used on a large scale in the wood preservation process, it is necessary to find a method, which will allow 2-DOG to be fixed in the wood. However, none of the agents tested in the project was able to fixate 2-DOG. In return, it was found that if glucosamine is fixated with sodium nitrite, the result was good, both before and after leaching.

Quite a few fungi can attack wood without causing any real decay. This is the case of the so called mould fungi. Some of them, however, can discolour the wood, and thereby reduce the utility value of the wood. The fungi producing bluestain belong to the mould fungi. Some mould fungi can attack certain types of pressure treated timber right after time preservation process, and they leave the wood discoloured (black). For instance Cladosporium resinae. Tests were made to find out if 2-DOG had an effect on this fungus. This was not the case, and the probable conclusion is that 2-DOG has no effect on mould fungi in general.

An area where 2-DOG is likely to be marketed immediately, is in the prevention of fungus attacks in situ in buildings. Here, the leaching often will be minimal, and the wood decaying fungi generating brown rot is far the largest problem. The Dry Rot Fungus, attacking both wood work and masonry, is especially harmful. The traditional combating of fungi includes an extensive chemical treatment of the masonry, for example with boron diffusion preservatives. Some attacks of Dry Rot Fungus are also treated with heat as this fungus is sensitive to high temperatures.

2-DOGs potential as an active ingredient to eliminate the Dry Rot Fungus is not clarified. Its capacity as a surface preparation agent has been tested according to ENV 839, and the fungus' capacity to generate a strong surface mycelium renders time test invalid. Since 2-DOG generally has shown a great efficiency against the fungi generating brown rot, it is likely to be a potential means against the Dry Rot Fungus.

The project has shown, that 2-DOG is a potential active ingredient against the wood decaying fungi. When dissolved in water, it can be used for pressure treatment and protect wood from being attacked by wood decaying fungi in a 3% concentration. When combined with the complex binding agents, EDTA or tripolyphosphate, the concentration of 2-DOG can be halved to 1,5%. This type of treatment cannot resist leaching, but when treating with 5% glucosamine followed by a fixation with sodium nitrite, the effect is preserved against the fungi, even after leaching. The lower marginal value is yet to be fixed. However, it is significant that by possible preservation with nitrite at the preservation concerns there will be demand for documentation that nitrite can not be substituted because of toxicity and firing characteristics of nitrite.

2-DOG can be produced by the hydrolysis of chitin, which is the main constituent in the exterior skeleton of shellfish aid-insects, and which doesn't easily decompose in nature. There is the possibility of collecting the waste from the production of crabs and shrimps, and use it in an inexpensive mass production of 2-DOG. Calculations of the output shows, that 1 kg of shrimps results in 100 g of shrimp shells. This would yield approximately 75 g of 2-DOG. Royal Greenland's annual production of shrimps, including shells, amounts to about 18.000 tons. Consequently, this production could theoretically result in the production of 1350 tons of pure 2-DOG. Even more could be produced, if the fishery industries in other countries were to be included. The total estimated sale of proofing compounds on a worldwide basis is of 550.000 tons (UNEP). These 550.000 tons are active substances and are to be compared with the 1.350 tons of 2-DOG. If you reckon with the fact that the wood should be preserved for protection against attack of brown rot fungi this would correspond to the fact that 650.000 cm³ could be preserved - corresponding to the demand in Denmark and Sweden.

The active substance, 2-DOG, which has proved to be a highly potential substance when it comes to the prevention and the combating of wood decaying fungi, has been evaluated according to the Danish Regulation of Pesticides elaborated by the Ministry of Environment and Energy (Bekendtgørelse nr. 768 af 23. august 1994). A literature research in the databases HSDB and TOXLINE has been performed. Based on the literature found, the qualities of the substance have been assessed. A number of data need to be found and clarified before time product can be approved. The production of the substance might give some problems in regard to working conditions (allergy) and environmental problems caused by potassium nitrite. Furthermore, the use of sodium nitrite, which is toxic and firing and can generate nitro gasses, will set up special demands to the process. The potential enviromental problems by production and preservation are not sufficiently illustrated in this report.

PART 2

Biocorrosion of building facades and ornaments is a problem, which today is treated by using biocides aid substances, which consolidate the weather-beaten surface. The decay of the surfaces is due to both bacteria, fungi and larvae. An account of the direct influence, which these organisms have on the surfaces, has been given. Furthermore, an account has been given of the physical-constructive initiatives, which can be undertaken in order to prevent the establishment and the further development of the biocorrosive factors and the consequences hereof. The presence of moisture is essential for the establishment of the decaying organisms. This is why many surface treatment products act to reduce the moisture pickup and in certain cases consolidate the surface. Such a treatment is often combined with a biocidal treatment. For this purpose, products based on water and on organic solvents exist.

In the development of new products for the prevention and the combating of biocorrosion of building facades, consideration is necessary of factors beyond the usual demands made on wood proofing compounds in relation to environment, efficiency, durability and economy. The products may neither discolour the surfaces nor physically or chemically damage the rnaterials, neither on a short-term nor a long-term basis. A possibility would be to develop 2-DOG in such a way, that it could be used as an active substance. However, The Department of Biotechnology has not run tests with this group of organisms, bacteria, lichens and certain fungi, which are relevant here. Furthermore, a solution to the fixation problem has to be found before 2-DOG can be put into use.

A second possibility consists in a method, which was patented in 1984: the surface is treated with copper salt followed by a treatment with a higher fatty acid soap, which binds the copper. This method seems to be cheap, and according to the information given, without any damage to the surface, but a documentation of the efficiency and durability is lacking.