Paul B. Marsh

The Fungi Concerned in Fiber Deterioration II: Their Ability to Decompose Cellulose

On the basis of a survey of the literature and of test results here reported on more than 400 fungus isolates, cellulose-decomposing activity is shown to be very widely distributed but not universal among the fungi. It occurs with a high degree of regularity among isolates of certain genera-e.g., Alternaria, Chaetomium, Curvularia, Fusarium, Gliomastix, Helmintho sporium, Humicola, Memnoniella, Stachybotrys, and Trichoderma, and probably with equal fre quency in other genera which have not been so extensively studied. It occurs in a greater or smaller number of species in many of the several groups or subdivisions of the genus Aspergillus but apparently not in all of them, in a much smaller but rather widely diverse group of species in the genus Penicillium, apparently not at all in Mucor, Rhizopus, and other genera of the Mucoraceae, and probably only rarely among the actinomycetes. Tests on Cladosporium herbarum show that the temperature optima for growth of isolates of this fungus are in general distinctly below the approximately 30°C used by several other workers in experiments with it; this fact is believed to account, at least in part, for the poor cellulose-decomposing activity shown by it in their tests. Tests on Pullularia pullulans have failed to detect cellulolytic activity.

The Fungi Concerned in Fiber Deterioration I: Their Occurrence

A review of the literature and certain new findings are presented which relate to the types of fungi which occur on cellulosic textile fibers under various practical exposure conditions. Numerous observations, some original and others assem bled from the literature, indicate that the following fungi are commonly found growing on fibers in particular types of situations : Alternaria, Cladosporium herbarum, and Fusarium (especially F. moniliforme) on cotton which has undergone weathering in the field before harvest; Alternaria and Cladosporium herbarum on cotton fabric in relatively short- term moderate- or high-light weather exposures, with Phoma and related forms, Leptosphaeria and related forms, and Pullularia pullulans appearing after longer periods under the same conditions; Alternaria, Cladosporium herbarum, Pul lularia pullulans, and, under some conditions, Fusarium on dew-retting flax and hemp; species of Aspergillus, Peni cillium, Stachybotrys, Chaetomium, and probably other fungi on cotton and other natural fibers in unprocessed or in textile form in humid storage; Aspergillus fumigatus on jute which has undergone microbiological damage in the bale; Halo phiobolus and certain other unusual salt-water-adapted forms on decaying cordage in marine exposures. Fungi other than the above-named may occur commonly under the conditions mentioned, but if they do this appears not to have been reported frequently or in any detail in the literature. Soil- contact exposures are believed to involve a very wide range of fungus forms, including numerous genera and species which have not been observed to occur commonly in mod erate- or high-light above-ground exposures. Information is presented which indicates that resistance on the part of the fungus to sunlight is an important factor in determining which fungi grow on fibers in different types of exposures. Differences among the fungi in moisture requirements and in temperatures favorable for growth are also important.

Microscopic Observations on Cotton Fibers Subjected to Enzymatic Degradation

Letters to the Editor Short communications in the form of Letters to the Editor are intended to provide prompt publication of significant new research results and to permit an exchange of views on papers previously published in the JOURNAL. These communications are not submitted to formal review as are research papers, and the editors do not assume any share of the author’s responsibility for the information given or the opinions expressed. When work previously published in the JOURNAL is the subject of critical comment, the authors of the original paper are given an opportunity to submit a reply, which will be published concurrently when possible.

Wax Content as Related to Surface Area of Cotton Fibers

Among a group of 62 essentially unweathered fiber samples from American upland cotton plants of different inherent and environmental background, percent wax was found to be rather closely proportional to surface area per unit weight of fiber as determined by the air-flow method of Sullivan and Hertel [22]. The weight of wax per unit of fiber surface was thus a relatively constant quantity, although not an absolutely constant one, among these samples. Results of melting-point determinations did not suggest the probability of important qualitative differences in wax composition at the time of boll opening among the several American upland cottons studied, the sole exception encountered being the high-melting-point wax from the green-lint high-wax cotton previously reported by Conrad [6]. In a group of twelve Sea Island hybrids, both the amount of wax per unit fiber surface and the wax melting points were similar to the results obtained for American upland types. Five Indian cottons all had very low wax percentages; their surface areas were below the normal range of the method for surface-area determination. Weathering of cotton in the field before harvest resulted in higher wax contents as measured by the Conrad [7] method and lower wax melting points than were found for similar but un weathered samples. Further work is required to indicate the nature of the causal factors in volved in this change which occurs during weathering.

Mildew- and Rot-Resistance of Textiles

Rotting was a problem with sandbags used for barricade purposes. Tents were exposed in moist tropical climates conducive to microbiological fiber deterioration. Military fabric items of many kinds were often of necessity treated very roughly in use, being commonly smeared with mud, rolled up and packed wet, or left for long periods in poorly ventilated storage. U. S. Army procurements included more than 250,000,000 yards of rotproofed sandbag fabric [57] , millions of yards of mildewproofed tent fabric ( 59, 82], and large amounts of mildewproofed material for jungle hammocks [59~, insect netting [59~, and camouflage nets. Major amounts of mildewproofed webbing, thread, and rope were also used. Although a number of important problems relating to the mildew-resistance of textiles and textile fibers

The Influence of Weathering Prior to Harvest on Certain Properties of Cotton Fibers

Most of the.commercial cotton fiber produced in the United States is subjected to a period of from one to many weeks of exposure to the weather before it is harvested from the plant. Such weathering has been shown in prior work to be a cause of changes in the wax on the fiber [19], in the fibers swelling behavior in alkali [22]. and, under humid conditions, in the pH of water extracts of the fiber [21]. Subsequent investigation now has revealed that a number of other fiber properties also may undergo change during preharvest weathering. These properties include moisture regain at constant relative humidity, dye absorption, content of water-soluble reducing substances, browning tendency, rate of wetting in a water-alcohol mixture, length, strength, and susceptibility to enzymatic decomposition. As might have been expected, the X-ray angle, as defined by Berkley and co-workers [4], showed little if any alteration. Several of the fiber properties which change during weathering have been measured on commercial fiber samples and the results found to show a relationship to the grade of the fiber. Further work is in progress to analyze the nature of the above fiber property changes and to detect other changes which may occur. A rapid and practical test for measuring the water-soluble copper-reducing constituents in raw cotton fiber is described.

Bacterial Counts on Commercial Raw Cotton from the U.S. Crop of 1980

A series of 143 commercial cotton fiber samples of widely varying grade from the 1980 U.S. crop was tested for bacterial content because of possible relevance of bacteria to byssinosis. Much sample-to-sample variation occurred in counts for total, gram-negative, and coliform bacteria, even among samples of the same or similar grade and geographical origin. Ratios of the three bacterial categories to each other within single samples also varied widely. Total bacteria ranged from 10,000 to 290,000,000 per gram of fiber.. Especially high counts were found in some spotted and tinged samples, but total bacterial numbers of more than a million per gram of fiber were encountered even in the better white grades. Bacterial numbers were not correlated with fiber pH. Most samples contained residual water-extractable materials capable of supporting addi tional bacterial growth. Bacterial counts on raw cotton fiber, as reported in the literature, were reviewed and found to be generally in the same range as those shown here.

Further Counts of Bacteria on U.S. Commercial Raw Cotton Fiber

As a result of a continuing interest in bacteria as a possible cause of byssinosis, previously reported counts of bacteria on U.S. cotton have now been extended. Counts have been made on 144 classers samples from the 1981 crop by methods used previously with samples from the 1980 crop. The 1981 crop again exhibited great sample-to-sample variation in total bacteria and gram negatives within the same grade and growth area. Gram-negative bacteria were found at a million or more per gram of fiber in some classers samples from the Southeast, Midsouth, and Texas-Oklahoma. Cottons from Californias San Joaquin Valley, however, consistently showed bacterial counts much lower than the national average, continuing a trend shown in the 1980 crop. No constant or even near-constant proportionality occurred between numbers . for total bacteria and for gram negatives. In an additional series of 80 samples from Cone Mills Corporation, California cottons again showed exceptionally low bacterial counts. Bacterial numbers did not vary in any constant relation to the fibers micronaire value.

Microscopic Observations on Fungi Associated with Cotton Boll-Rot Fibers

Cotton boll-rot fibers were examined microscopically to determine the manner in which fungi grow on them. Cellulose decomposing boll-rot fungi wound around the fibers, paralleling closely the helical structure of the secondary wall; non-cellulose decomposers did not wind. Cellulose decomposers penetrated through the secondary walls and grew in the lumens; non-cellulose decomposers did not. Some fungi formed spores in the lumens. Mounting fibers in NaOH solutions made fungi easier to see, as did differential staining with Niagara Sky Blue 6B or mounting in cuprien. The cuprien caused swelling of the cellulose or its complete solution without visibly attacking the fungus.

A Review on the Kinds of Potentially-Byssinogenic Gram-Negative Bacteria that Occur on Raw Cotton Fiber

Byssinosis is a pulmonary problem experienced by some workers in areas of textile mills where cotton, flax, or other fibers are being mechanically processed prior to spinning. It has long been associated with dust in the air of the mill. As it occurs in U.S. cotton mills, byssinosis has been attributed at least in part to a gram-negative endotoxin-bearing bacterial component of the dust dispersed from fiber into air (Jacobs and Wakelyn, 1988). Bacteria, including gram-negatives, have been shown to grow on the fiber in open bolls before harvest; such growth occurs especially during rainy weather (Simpson and Marsh, 1986; Simpson et al., 1987b). Bacterial growth on fiber is minimal in the San Joaquin Valley of California, where the weather is exceptionally dry in the period between boll opening and harvest (Simpson and Marsh, 1985). Until recently, the gram-negative bacteria on commercial cotton fiber have been only incompletely identified. We briefly review here the identification of such bacteria and discuss practical implications of these findings in relation to the byssinosis problem.