International Biodeterioration最新文献

Detailed studies have clearly demonstrated that few biocides can be considered now as general cell poisons. Biocidal action may result through physicochemical interaction with microbial target structures, specific reactions with biological molecules, or disturbance of selected metabolic or energetic processes. Mechanism of action studies, if intelligently applied, can provide direction to the development of novel biocides and biocidal systems.

Polymer emulsions, also referred to as polymer dispersions, latices, latex emulsions or latex dispersions are used in an increasingly wide variety of applications including production of emulsion paints, adhesives, paper and textile coatings, non-woven fabrics and carpet-backing compounds.

The pH of these polymer emulsions varies greatly, being acidic in the case of some EVA and PVA types whilst some acrylic, styrene acrylic and styrene butadiene products can be relatively alkaline.

Many types are susceptible to biodeterioration by micro-organisms, although growth will depend on a number of environmental and nutritional factors.

Once growth occurs, a number of effects may be noticed including viscosity changes, production of gases and odours, colour changes and enzyme production with concomitant effects on manufactured end products.

Microbiological infection and its effects can be avoided by controlling the quality of and use of less susceptible raw materials and intermediates, by improving plant design, cleanliness and hygiene and by the use of effective, broad spectrum biocides.

An aqueous antacid formulation normally protected from the growth of microbial contaminants, including opportunist pathogens, with the synthetic preservative Bronopol (2-bromo-2-nitropropane-1,3-diol) became contaminated with Fusarium solani. Contamination with F. solani, at levels below those which would be detected by routine quality control, resulted in the loss of antimicrobial protection. Not only was F. solani relatively resistant to Bronopol but it was able to grow and sporulate in the liquid antacid formulation, in which Bronopol was the only demonstrable source of nitrogen.

In tanneries microorganisms are provided with environments suitable for growth. The proteins and fats in the hide represent an ideal source of nutrients for bacterial and fungal growth. In particular, pickled pelts, wetblues and vegetable-tanned moist leathers are prone to mould growth when stored or shipped.

In the past, preservatives were expected primarily to provide effective protection, but in more recent years concern over potential ecological hazards has become more important. Worries over environmental pollution have led to pentachlorophenol-containing preservatives being replaced in most tanneries in Europe.

This paper presents some new aspects of leather preservation with modern heterocyclic fungicides.

The analysis of fungicides on wetblues shows the penetration behaviour of the heterocyclics throughout the pelt. The advantages of the combination of penetrating and surface-active materials are stressed.

Results of laboratory experiments with new fungicides are presented. The fungicidal effectiveness on wetblues has been examined by simple microbiological and analytical tests.

Increasing legislative requirements and the necessity for greater environmental acceptability have emphasised the need for either new, or carefully selected blends of existing, biocides. Blending of existing biocides offers a means of providing broad-spectrum antimicrobial activity, the possibility of synergy and avoids the high cost of screening new molecules. This paper discusses the advantages and disadvantages of this approach and illustrates the properties of new formulations utilising mixtures of commercially available biocides. Laboratory data are presented on the performance of formulations for the preservation of cosmetics and toiletries.

The performance of new formulations for use as industrial biocides in metal-working fluids and water treatment applications is discussed.

A rapid soil burial method for assessing the susceptibility of polyurethanes to biodeterioration was developed. The time of the test was reduced by prestressing the polyurethanes. The degree of deterioration was measured by following changes in the appearance of the polyurethanes and in selected physical properties. It was found that pre-stressing produced significant reductions in the tensile strength of a known susceptible polyurethane after burial in soil for 2 weeks. The reduction was greater than that found with unstressed polyurethanes buried for 26 weeks in active soil. Changes in tensile strength were less after burial for 4 weeks in sterile soil than after burial in active soil for the same period. The results suggest that deterioration of polyurethane during soil burial is a result of both chemical and microbial action.

The storage potential of the African pear (Dacryodes edulis (G. Don.) H. J. Lam.) (Burseraceae) was investigated using four fruit types. At ambient temperatures (28·5–30°C), those enclosed in either paper or polythene bags could be stored satisfactorily for 3–8 days, after which they deteriorated rapidly. Storage life was increased at lower temperatures, but injury due to chilling was observed at −5°C. At 15°C, fruits dipped in palm oil before being packaged were of better quality and retained their firmness longer than fruits dipped in a 500 ppm benlate solution. Storage in moist sawdust, wood-shavings or water were the least effective in extending shelf-life. Variation among fruit types in their response to storage treatment was observed.