International Biodeterioration最新文献

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.

Mycotoxins can have an impact on economics by causing losses in farm animals or giving rise to difficulties in their management, or by rendering a commodity unacceptable in national or international trade, because it does not conform with national criteria laid down for maximum tolerated levels of certain mycotoxins. The formation of mycotoxins in human food or animal feeds can occur as a result of postharvest sp materials badly stored, or preharvest as a result of invasion of a crop plant by a mycotoxigenic mould which may have a pathogenic or symbiotic relationship with the plant. There is at least one situation (facial eczema of sheep) in which a mycotoxin (sporidesmin) is produced in the field but on dead plant litter rather than in the living plant.

Given sufficient economic resources there should be no problem in controlling the postharvest formation of mycotoxins in storage, but in tropical developing countries these resources may not be available and problems do still occur. The formation of mycotoxins in the field may be far more difficult to control and may require quite radical changes in agricultural practice.

A cooling tower water system at the Madras Fertilizers Company, Madras, India was investigated for the occurrence of microfungi over a period of 108 weeks from March 1978 to April 1980. The make-up water, cooling tower water and effluent were baited with pine (Pinus patula Schl. & Cham.) and beech (Fagus rhamnifolia A. DC.) wooden test blocks. Observations were made at 6-weekly interval for the qualitative and quantitative changes in the species composition. The study showed that a cooling tower water system in the tropics provides a suitable environment for the growth and development of a variety of microfungi. Differences in the physical and chemical factors (e.g. temperature, effluent concentration, etc.) in cooling tower water systems have a profound effect on the composition of the mycoflora. Generally beech test blocks attracted a greater variety of fungi than pine. A total of 106 species belonging to 65 genera were isolated from the cooling tower water system, which were classified into ‘primary’, ‘secondary’ and ‘sporadic’ colonisers on the basis of the sequence and frequency of their appearance on the test blocks. Further, based on the percentage frequency the fungi were categorised into ‘dominant’, ‘common’, ‘frequent’, ‘occasional’ and ‘rare’ forms. Some of them reported in this study are already known for their potency to cause soft rot and white rot in wood.

Commercial enzyme preparations, viz. Pectinex ultra Sp-L and Flaxzyme consisting predominantly of pectinolytic enzymes were found to ret green jute ribbons within 48 h, producing fairly good quality jute fibres. The commercial enzyme Celluclast, consisting mainly of cellulase, hemicellulase and a relatively low proportion of pectinase was, on the other hand, ineffective in bringing about similar retting. A fiftyfold dilution of both Pectinex ultra Sp-L and Flaxzyme was able to ret ribbons of jute plants of 105–115 days old. producing fibres having a fineness in the range of 1.6–1.7 tex and a tenacity of bundles in the range of 23–25 g/tex. The fibres produced were totally free of barky root ends. Metal complexing agents such as citrate phosphate buffer and EDTA were found to stimulate enzymatic retting thereby helping to reduce effective enzyme concentration. The ret-liquor containing the retting end products were partially analysed. Amongst the monosaccharides, galacturonic acid was most predominant followed by glucose, arabinose, galactose and xylose; and amongst the gummy polysaccharides, pectin was most conspicuous.

A comparison of the ligninolytic, cellulolytic and hemicellulolytic abilities of an alkaliphilic white-rot fungus. Coprinus fimetarius, on wheat straw under varying conditions of solid-substrate fermentation is presented. The extent of fractional degradation (percentage of the original dry weight of the fraction) of straw under an optimized set of cultural conditions (pH 9·0, moisture 65%, temperature 37°C, period 21 days) was in the following order: lignin (45%), cellulose (42%), hemicellulose (27%). Urea nitrogen favoured the degradation of lignin as well as cellulose and hemicellulose up to a certain level (1·5% sterile urea or 3% unsterile urea on a dry weight basis) beyond which the degradation of lignin was relatively more adversely affected than cellulose. The addition of phosphorus and sulphur was found essential for selective lignin removal. Increasing the C:N ratio by addition of free carbohydrates resulted in an overall decrease in the degradation wherein cellulose utilization was the most affected event. The pre-treatment (physical or chemical) of the substrate caused a general increase in biodegradation of lignin, cellulose and hemicellulose. The degrading activity of the fungus declined with the scaling-up of the fermentation particularly under non-sterile conditions.

A survey was undertaken to compare the hot-water systms of four Scottish institutional buildings, two of which suffered severe corrosion of their copper pipe work. A number of parameters were investigated including temperature, dissolved oxygen concentration (DO) and assimilable organic carbon (AOC). Microbiological analysis was also carried out on the water supply and the inner surface of the pipes. The institutional buildings experiencing corrosion had a lower temperature and a higher AOC in their hot-water systems than those without this particular problem. These findings were similar to a 1987 survey, which suggested that the problem might be microbially induced corrosion.

A two-stage continuous culture model was used to mimic the corrosive environment of one of the institutional buildings. Using a microbial inoculum from the surface of the copper pipe work and filter sterilised water supplying the building it was possible to show that biofilm could readily be established up to 55°C. However at temperatures above 55°C the biofilm was greatly reduced.