1066-3622/02/4401-0096$27.00?2002 MAIK ?Nauka/Interperiodica?Radiochemistry, Vol. 44, No. 1, 2002, pp. 96?99. Translated from Radiokhimiya, Vol. 44, No. 1, 2002, pp. 92?95.Original Russian Text Copyright ? 2002 by Markov, Smirnov, Romanovskii, Tret’yakov, Khramov, Nugaeva, Lebedeva.????????????????????????????????????????????????????????????????????????????????????Microbial Degradation of Radioactively ContaminatedPolymer Films1G. S. Markov*, I. V. Smirnov*, V. N. Romanovskii*, V. E. Tret’yakov*,N. N. Khramov*, N. D. Nugaeva**, and E. V. Lebedeva*** Khlopin Radium Institute, Research and Production Association, St. Petersburg, Russia** Komarov Botanic Institute, Russian Academy of Sciences, St. Petersburg, RussiaReceived January 25, 2001Abstract?Microbial degradation of polymeric paint and varnish coatings is considered from the standpointof its application to deactivation of radioactively contaminated painted surfaces. Biodegradation of polymerfilms based on linseed stand oil, with mycelial microfungi Aspergillus, Penicillium, Trichoderma, Cladospori-um, and Alternaria is studied. Some strains demonstrated a sufficiently high radioresistivity. After applicationof small amounts of digestible nutrient to the film surface the selected strains of microfungi can be usedas destructors. Thus degraded areas of the films can be easily removed then by treatment with hot water.Study of microbial degradation of polymeric paintand varnish materials is of interest from the standpointof deactivation of painted indoor surfaces and facili-ties contaminated with radionuclides. The expectedadvantages of biotechnological methods of deactiva-tion over the known mechanical and physicochemicalmethods are relatively low cost and process simplic-ity. Until recently microbial degradation of protectivecoatings was considered as an undesired processwhich should be suppressed. In our case purposefuluse of microbial degradation of polymeric coatingscauses the need in searching for and selection of themost active strains of destroying microorganisms andalso in optimization of conditions for their cultivation.In this work we studied biodegradation of polymerfilms based on linseed stand oil using myceliummicrofungi.It is known that microfungi (micromycetes) areamong the most active biological destroying agentsfor natural and man-made materials [1, 2]. Fungi re-present a great kingdom of microorganisms charac-terized by the unique path of growth. Apical growthof fungal mycelium composed by thin branchingthreads (hyphae) favors the most extensive coloniza-tion and assimilation of a substrate. Growing on thesurface and penetrating to the substrate mycelia in-teract with the substrate, utilizing the substrate com-ponents and excreting metabolites. Being accumu-lated, fungal metabolites form a specific mediumpromoting substrate degradation. It was demonstrated[2, 3] that the most destroying agents for paint and????????????1Reported at the Third Russian Conference on Radiochemistry(St. Petersburg, November 28?December 1, 2000).varnish coatings are fungal metabolites representinga set of organic acids such as citric, fumaric, gluconic,tartaric, acetic, and oxalic. The optimal conditions forgrowth of mycelial fungi are high humidity and atemperature of 24?26?C. It should be pointed outthat many species of fungi can grow at even highertemperatures (?40?C). Generally, fungi demonstratediverse regulation mechanisms allowing their adop-tion to wide diversity of conditions.Among the known destroying agents for paint andvarnish coatings are micromycetes from such generaas Aspergillus, Penicillium, Trichoderma, Clado-sporium, and Alternaria [2], some species of whichwere selected by us as destructors for polymer filmsbased on linseed stand oil.Since these micromycetes were planned to use forbiodegradation of radioactively contaminated poly-meric materials, it was necessary to characterize theradioresistivity of the selected strains.It is known that the radioresistivity of microorga-nisms is primarily controlled by the radiation resist-ance of nucleic acids of the cells. First of all, ionizingradiation inactivates DNA of microorganisms, sothat the amount of undamaged molecules of nucleicacids, capable to ensure cell fission, can be reducedby several orders of magnitude. Inactivation occursby virtue of both direct and indirect radiation ef-fects. Generally, the kinetics of microorganism deathfollows the exponential law. Occasionally a delayshoulder is observed in the kinetic curve at lowdoses, which is due to operation of the cell reparationsystems. It is known [4, 5] that the radioresistivity
