Susceptibility of Cellulose to Attack by Cellulolytic Microfungi after Gamma Irradiation and Ageing
| Main Authors: | , , , |
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| Format: | Article |
| Language: | English Slovak |
| ISSN: | ISSN 0034-5806 |
| Online Access: | http://www.viks.sk/chk/res_3_03_145_151.doc |
| Abstract: | SUMARIES. In the context of broader research looking at the decontamination of books and documents stored in libraries and archives, the present paper describes the effect of different y-rays doses on the growth of a fungus responsible for the deterioration of paper (Penicillium chrysogenum Thorn.), on cellulose paper (Whatman). Irradiation was carried out with a Co-60 source. After irradiation the samples, placed onto solid carbon free culture medium, were inoculated with conidia of P. chrysogenum. After incubation at 25°C for 7 days fungal growth was measured by evaluating the ergosterol content. The results show that the high y-rays irradiation induce some alterations in the cellulose macromolecule that influence growth of the fungus responsible for paper deterioration. This phenomenon, particularly evident with the higher doses (100 and 200 kGy), is not appreciable when the irradiation dose is maintained at low levels (<10 kGy) suitable for a practical application of radiation technology for paper disinfection/disinfestation. The effect of accelerated ageing after -/-irradiation on cellulose inoculated with conidia of P. chrysogenum was also tested. CONCLUSION. Measuring the amount of ergosterol we can directly estimate the developed bio-mass of P. chrysogenum and indirectly the susceptibility of cellulose, as this polymer is the main source of carbon for the fungus9. The fact that P. chrysogenum grew better on more depolimerised cellulose after y-rays irradiation than on samples with unchanged cellulose confirmed the already well-known effect of ionising radiation on the degree of depolimerization of cellulose'7,8,11,12. It became evident that high y-ray irradiation induced components into paper which were related to the absorbed dose, and some structure alterations that can affect fungal growth. This phenomenon was particularly evident at very high doses (100 and 200 kGy). 3 and 10 kGy, however, which are suitable doses in the practical application of radiation technology for the decontamination of paper, seems to have had only a moderate or no effect at all on fungal growth. We know from the literature13'14 that fumigation by ethylene oxide - until today the most used biocide treatment for library and archive materials - also makes these materials more susceptible to fungal attack. The results showed some differences from those reported in our previous work9. This may be due to die source of the inoculum used in the experiments: fresh culture in one set, a culture coming from lyophilized fungus in the other, resulting in different growth rates. However, the capability of die fungus to colonize well on cellulose was assessed prior to performing all the experiments. In our experimental conditions cellulose modification due to y-ray treatments seemed to be significant for fungal growth rates only at die higher doses (100-200 kGy), while no synergistic effects were detected with the associated treatments (irradiation and ageing). This suggests that P. chrysogenum demonstrates the same behaviour towards bodi non-aged and aged cellulose. Widi our experimental conditions we tried to reproduce the conditions that would occur in a real situation such as a flood, i.e. in the presence of all - nutritional and environmental - conditions necessary for fungal growth. The results show that, under these conditions, cellulose that has not been irradiated would degrade within a short period. Hence it follows that very contaminate material requires immediate intervention in order to minimise its damage. |
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| ISSN: | ISSN 0034-5806 |
