International Biodeterioration最新文献

Microbiological agents, such as bacteria, actinomycetes, and fungi, degrade cellulose. The most severe deterioration in indoor environments is primarily caused by cellulolytic fungi, resulting in loss of fiber strength and actual material failure. Other microbial spoilage can occur as a result of the permanent staining from pigmentation and mycelial penetration by both cellulolytic and non-cellulolytic fungi, the latter using food sources ranging from starch sizing to surface dirt, and oils. Much has been written concerning biocidal testing against these microfungal agents from an industrial point of view; less from a conservation standpoint. This paper submits a limited review of current literature (c. 25 years) focusing on the information and its relevance for the conservator. The following topics related to cellulosic deterioration by fungal microbes are covered; 1. current theories about the mechanism of cellulolytic attack; 2. biocides which may be employed in fungal control; and 3. choice of environmental conditions as a means of static control of fungal biodegradative agents. An annotated reference list is provided.

A microbiological study of four series of wood samples taken from three areas (heartwood, sapwood and bark) of six species of timber logs (American basswood, black cherry, black locust, red oak, soft maple, and white poplar) during the summer, fall, winter and spring of 1987–1988 has previously been reported. The samples were analyzed for aerobic bacteria. Gram-negative bacteria, fungi and bacterial endotoxin. The present paper focuses on the yeasts and yeast-like fungi (e.g. Aureobasidium pullulans) isolated from these samples. The predominant species varied with the season, tree, and location. Pichia (Hansenula) sp. predominated, particularly in the August samples and especially from the sapwood of basswood, locust and cherry. Candida sake and other members of group 7 of the genus Candida were especially common in the samples taken in May from the sapwood and heartwood of maple and oak logs. Cryptococcus laurentii and Rh. glutinis were the predominant members of Cryptococcus and Rhodotorula, respectively, isolated from these samples.

Growth and development of a variety of fungal strains on limestone samples impregnated with the commercially available rock consolidants Steinfestiger H and Elastosil E-41 was studied. It was found that treatment with silicone resins did not prevent fungal growth. On the contrary, growth was, in many instances, more intensive on Elastosil E-41 impregnated stones than on the untreated samples. Using scanning electron microscopy (SEM) it could be demonstrated that growth of mycelia and the sporulation of fungi took place on both freshly prepared rock surfaces and in the interior of the stone, including the films of resin themselves. Some of the fungi growing on treated surfaces caused a significant decrease or the complete loss of the water-repellent properties initially achieved by the impregnant. We could observe that some strains were involved in the degradation of limestone and in apatite biogenesis. The factors stimulating microbial growth on treated rocks are discussed.

A unique opportunity became available to investigate the mold species isolated from a formaldehyde embalmed and subsequently tanned excised elephant trunk. The long-term preservation with glutaraldehyde was also investigated. The isolated mold species were identified as Penicillium notatum, P. variabilis, P. purpurogenum, and Aspergillus niger. Minimal inhibitory concentrations were determined for all species using formaldehyde as well as glutaraldehyde. The latter was selected due to its widespread and legally acceptable use as a preservative, fixative, and sterilant. Trivial differences between glutaraldehyde and formaldehyde, based on molar levels, were noted. The trunk was preserved for approximately 1 year in a 50% ethylene glycol solution with 0.9% glutaraldehyde, after which no viable organisms were found. Subsequently, the fluid was removed and thymol and a dessicant were placed in the sealed display case. One year later, the trunk was examined for fungi, with no growth detected. These findings may be useful for future museum staff investigators who encounter similar infection in other preserved specimens of various sizes.

Several aspects of the biodeterioration of stone are reviewed, including general deterioration mechanisms, deterioration attributed to specific biological organisms, conservation case histories, and treatment options. The literature is cited with emphasis on historic monuments.

The relative tolerances of the vegetative cells and ascospore-rich suspensions of two yeast species to sanitisers commonly employed in the food industry were compared using a suspension test procedure. The yeasts. Saccharomyces cerevisiae and Pichia anomala had been isolated from a bakery environment and implicated as potential spoilage microorganisms. The sanitisers included two quaternary ammonium compounds, an amphoteric-based sanitiser and a hypochlorite. The test assessed the ability of the disinfecting agents to destroy the ascospore-rich populations within the times and concentrations recommended to sanitise surfaces in food production environments. Vegetative cells of S. cerevisiae were more sensitive than the vegetative cells of P. cerevisiae were more sensitive than the to be more susceptible to sanitiser challenge than the ascospore-containing populations.

This paper gives a brief overview of the effects of hydrogen sulphide on marine corrosion. It draws on both the microbial corrosion literature and the metallurgical fatigue and fracture literature to bring together the various effects of hydrogen sulphide including toxicity and deterioration in product quality as well as surface corrosion and stress/fatigue-corrosion interactions. The latter are seldom considered in studies of microbial corrosion but are the prime failure modes on offshore structures.

Utilizing short-term (5-week) laboratory exposures under conditions of high relative humidity, samples of polymers and resins important in preserving art materials, particularly stone, were evaluated for their ability to support fungal growth. Growth of the organisms was ascertained by macroscopic, microscopic, and physico-chemical changes of these materials over a 5-week testing period. Based upon their sensitivity to fungal deterioration, the polymers and resins tested were quantitatively ranked in order of least to most susceptible to biological attack.