International Biodeterioration最新文献

A filtrate from a Streptomyces fradiae culture was used as a source of highly active (2000 U/g) and stable proteolytic enzymes. The preparation was used for the degradation of sheep's wool, chicken feathers, guinea pig hair and human hair. The effects of the enzyme action were controlled under light and scanning electron microscopes. The degradation was quickest in the case of wool (after 24 h), then chicken feathers and guinea pig hair (four days). Human hair underwent degradation after 17 days. The radical changes in the structure of the materials indicate a possibility of employing the proteolytic preparation of Streptomyces fradiae on a technological scale.

Digestion of structural components of the wool fibre in the alimentary system of Anthrenus flavipes larvae has been studied by optical and scanning electron microscopy. The larvae have been shown to bite off wool fragments of varying length ranging from 20 to 100 μm which rapidly pass through the foregut and accumulate in a large sac-like midgut. Digestion of outer cuticular scales occurs in the midgut region. Large numbers of symbiotic bacterial cells facilitate extensive digestion of keratin fibrils of the cortex in the ileum region, resulting in complete structural disintegration of the wool fibre. Actively feeding amoeba-like protozoans gradually replace the bacterial flora in the posterior ileum and rectum regions. Digested wool components and microbial biomass gradually become compact due to absorption of nutrient fluid in the hindgut. In the final stage of digestion, the compact faecal pellets consisting of remaining undigested and partially digested wool fragments and the microbial biomass, containing mainly protozoans and lysed and intact bacterial cells, lie in a chain in the rectum before excretion.

Japan's climate, with several months of high temperatures, and high humidity, is well suited to the growth of various kinds of fungi. They grow not only on food, wood, and textiles, but also on paintings.

We have examined a variety of instances of deterioration caused by the growth of fungi on paintings and have isolated and identified more than a hundred of these fungi. Of these, the typical ones are Alternaria, Cladosporium, Fusarium, Aspergillus, Trichoderma and Penicillium.

Since 1982 we have studied a fungicide-containing varnish to test its ability to inhibit fungal growth. The varnish, made from synthetic resin containing Vinyzene, a fungicide, was sprayed on about 100 paint samples. Annual observations have confirmed that it has a fungicidal effect.

This paper reports on the effect of the Vinyzene-containing varnish on paint and its utility as a fungicide.

The ability of microorganisms to decompose aromatic compounds, many of them with intrinsic antimicrobial power, has been known from the beginning of the 20th century. The early work arose from the finding that the soil biocides disappeared from the soil and this was traced to their metabolism by soil microorganisms. This finding gave rise to extensive biochemical investigations into the mechanisms of decomposition.

This degradation has been found in preservatives and is well documented as one of the possible reasons for preservative failure. This paper highlights some examples of this phenomenon.

This paper presents the results of a study on the lichen vegetation of the Roman aqueduct, Anio Vetus, located in S. Gregorio near Rome. The study is based on 12 surveys. The data obtained have been submitted to numerical classification and ordination. Different lichen communities can be distinguished on the basis of the results. The ecology of each community and the damage caused to the monuments are discussed on the basis of the ecological indices proposed by Wirth. The intensity of solar radiation seems to be the main facotr leading to decay on the Anio Vetus aqueduct.

Microorganisms are frequently found on deteriorated coatings and their deteriogenic action can be demonstrated by testing them against sound coatings of the same composition. No blistering or loss or adhesion occurred on either biocide containing coatings or coatings tested under sterile conditions. The mechanism of the attack is largely unknown. It has been assumed previously that to bring about loss of adhesion and blistering, the microorganisms must penetrate the coating and act from beneath the film. However, observations reported here indicate that microorganisms attack the coating from the surface thereby changing its chemical and physical properties. It has been demonstrated that these effects are generated by metabolites excreted by these organisms.

Raman microscopic analysis has proved effective in the interpretation and characterization of both the physical and chemical nature of the lichen/substratum system. In the case of Dirina massiliensis forma sorediata, a lichen causing extensive damage to Italian frescoes, the lichen-generated encrustation has been proved to be composed essentially of calcium oxalate. This particular biodeterioration process may be slowed down, or indeed inhibited, by the presence of certain compounds, as yet undertermined, used in the preparation of surfaces and the painting of frescoes. From a conservator's point of view, Raman microscopic analysis uses microscopic samples in the nanogram-picogram range and is non-destructive of the sample.