No description available.

No description available.

M.S. / Biochemistry / The white-rot basidiomycete Phanerochaete chrysosporium produces intracellular soluble and particulate ß-glucosidases and an extracellular ß-glucosidase. The extracellular enzyme is induced by cellulose but repressed in the presence of glucose. The molecular weight of this enzyme is 90,000. The K [subscript m] for -p-nitrophenyl-ß-glucoside is 1.6 x 10[superscript -4] M; the K [subscript 1] for glucose, a competitive inhibitor, is 5.0 x 10[superscript -4] M. The K [subscript m] for cellobiose is 5.3 x 10[superscript -4] M. The intracellular soluble enzyme is induced by cellobiose; this induction is prevented by cycloheximide. The presence of 300 mM glucose in the medium, however, had no effect on induction. The K [subscript m] for p-nitrophenyl- ß -glucoside is 1.1 x 10[superscript -4] M. The molecular weight of this enzyme is about 410,000. Both enzymes have an optimal temperature of 60°C and an E [subscript act] of 9.15 kcal/mole. The pH optima, however, were 7.0 and 5.5 for the intracellular and extracellular enzymes, respectively.

No description available.

No description available.

No description available.

Photodegradation of southern yellow pine, its mechanisms and means of prevention were studied. Changes in brightness and color were recognized when wood was exposed outdoors or to ultraviolet light. Scanning electron micrographs showed that most of the cell walls on irradiated transverse surface were separated at the middle lamella region. Half-bordered pits and bordered pits on irradiated longitudinal surf aces were found to be readily destroyed by ultraviolet light. It was also noted that progressively granular surfaces formed on the cell walls of latewood in response to irradiation with ultraviolet light. Spectrophotometric studies on the chemical changes of exposed wood, lignin, and cellulose revealed that photochemical reactions primarily took place in lignin, leading to the generation of carbonyl- and carboxylic-containing degradation products of low molecular weight. Formation of hydroperoxides, one of the mechanisms attributed to the photodegradation of wood, was illustrated from iodometry UV absorption studies. The hydroperoxide concentration at the wood surface increased when wood was irradiated in the presence of singlet oxygen generators. The hydroperoxide concentration decreased when wood was irradiated in the presence of singlet oxygen quenchers. These findings imply the participation of singlet oxygen and the formation of hydroperoxides at the photo-irradiated wood surfaces. It was found that the photodegradative effects on wood surfaces were mitigated by treating wood surfaces with aqueous solutions of chromic acid or ferric chloride, by treating with penetrating chemical agents such as trial, glycol and 1-octadecanol, or by coating with clear polymeric ultraviolet stabilizers such as homo- and copolymer of 2-hydroxy-4(3-methacryloxy-2-hydroxypropoxy)benzophenone. Experimental results showed that the polymeric ultraviolet stabilizers provided the best protection of the treatments tried, and were themselves stable and resistant to photodegradation. Possible chemistry and mechanisms of protection provided by organic and inorganic chemical agents are discussed. / Ph. D.

Previous research on coarse woody debris (CWD) indicated that moisture content and initial heterotrophic colonization of decaying wood can affect the decomposition process. Six heterotrophic treatments were created to simulate the effects of physical penetration of the bark and wood and the transmission of ascomycetes versus basidiomycetes into CWD. In 1995, 360 Douglas-fir (Pseudotsuga menziesii) were randomly placed at five replicate sites in old-growth stands. Each site had 6 heterotrophic (HET) x 2 moisture combinations (TENT). One set of logs representing the treatment combinations was used for sampling respiration and another set was used to measure volume affected by insect gallery excavations and fungal rot and to determine decay rates. Respiration was sampled three times during the summer of 2001. The results indicated that the HET treatments were no longer affecting respiration rates. Analysis of the average of the three sampling periods revealed no TENT effect but examinations of the individual sampling dates suggests that tented logs might have higher respiration rates than non-tented logs as summer progresses. In the aggregate, the TENT treatment reduced moisture content from 45% to 36%, a 20 percent reduction in moisture levels. The HET and the TENT treatments did not affect decay rates. The mean density change for the logs was -0.072 g/cm�� �� 0.03 and the mean decay constant was 0.026 �� 0.011. The TENT treatment did affect heterotrophic activity. The mean volume of wood borer excavation and extent of brown rot was higher in the tented logs (256 cm��) than in the non-tented logs (59.9 cm��). There was also a statistically significant interaction between the HET and TENT treatments. The largest differences in volume affected by wood borers and fungal rot were found in treatments that injected ascomycetes into the experimental logs. In sum, there was limited evidence that the differences in moisture content caused by the TENT treatment affected the decomposition process but the HET treatments appear to not be directly influencing decomposition after six years. The findings suggest differences in the initial community composition of heterotrophs have a decreasing impact on the decomposition process as it progresses. / Graduation date: 2004

Thesis (MSc)--University of Stellenbosch, 2007. / ENGLISH ABSTRACT: It is commonly known that a diversity of fungi, including yeasts, may occur on plant surfaces. Similarly, on fallen trees an ecological succession of different fungal species is known to occur during wood degradation. Some of these fungi may be pioneer fungi contributing to the initial degradation process, while others may be yeasts associated with the fruiting bodies of macro-fungi which in turn are able to utilize the more recalcitrant polymers in wood. Previously, it was revealed that an increase occurs in the wood degradation rate of certain white-rot fungi when co-cultured with selected yeast species. A well known inhabitant of decomposing trees is the white rot fungus Pycnoporus sanguineus. It was found by some that this fungus is capable of selective delignification while growing on the wood of poplar trees, while other authors found a simultaneous delignification pattern on Eucalyptus grandis trees. In the latter case cellulose and lignin are degraded simultaneously. We were interested in how yeasts occurring on the surface of P. sanguineus fruiting bodies, and the pioneer fungus Aspergillus flavipes, impact on wood degradation by this white-rot fungus. Restriction Fragment Length Polymorphisms (RFLP) analyses were used to obtain an indication of the species composition of the culturable yeast community associated with fruiting bodies of P. sanguineus. The impact of the most dominant of these yeasts species, i.e. Pichia guilliermondii and Rhodotorula glutinis, as well as A. flavipes, on wood degradation by P. sanguineus was then determined by analyzing the major wood components after growth of co-cultures on hot water washed E. grandis wood chips. Co-cultures of P. sanguineus with the other fungi were prepared by inoculating the wood chips, contained in solid state bioreactors and supplemented with molasses and urea, with the an appropriate volume of fungal inoculum, resulting in an initial moisture content of 60%. After two weeks of incubation at 30°C with constant aeration, the chips were harvested. Standard protocol (TAPPI Standard Methods), commonly used by the paper and pulp industry, were then employed to determine the percentage cellulose, Klason Lignin, as well as polar and solvent-borne extractives in the chips. The resulting data were analyzed using box plots, as well as biplots. No degradation of Klason lignin was observed, while the percentage cellulose did decrease during fungal degradation. Taking into account the inherent shortcomings of the Klason Lignin determination, the results supported the findings of others that P. sanguineus shows a simultaneous delignification pattern while growing on E. grandis wood. In addition, it was found that the yeasts played no significant role in the degradation ability of P. sanguineus, while A. flavipes showed an antagonistic effect on P. sanguineus with respect to cellulose degradation. However, it was clear that the analytical methods used in this study were inadequate to accurately determine fungal degradation of wood. In addition, it was obvious that the methods used did not distinguish between fungal biomass and wood components. Nevertheless, the methods provided us with a fingerprint of each culture growing on E. grandis wood, allowing us to compare the chemical composition of the different cultures and the un-inoculated hot water washed wood chips. The question, therefore, arose whether the effect of a particular coculture, on the chemical composition of wood, differs between tree species. Consequently, chemical alterations in different tree species, induced by a P. sanguineus / A. flavipes co-culture, were investigated in the next part of the study. Wood chips originating from four tree species, i.e. Acacia mearnsii, Eucalyptus dunnii, E. grandis, and Eucalyptus macarthurii, were inoculated with this co-culture. The culture conditions and subsequent analyses of the wood components were the same as in the first part of the study. From the box- and biplots constructed from the resulting data, it was clear that the chemical composition of each tree species were altered in a different manner by the coculture. Lignin content showed an apparent increase in A. mearnsii, while E. dunnii showed a decrease in cellulose content. The results indicate that wood of different tree species are degraded in a different manner and this phenomenon should be taken into account in selecting fungi for biopulping. / AFRIKAANSE OPSOMMING: Dit is algemeen bekend dat 'n verskeidenheid fungi, insluitend giste, op plantoppervlaktes mag voorkom. Dit is ook bekend dat 'n ekologiese opeenvolging van verskillende fungusspesies tydens hout-afbraak op omgevalle bome voorkom. Van hierdie fungi mag pionierfungi wees wat bydra tot die aanvanklike afbraakproses, terwyl ander giste mag wees wat geassosieer word met die vrugliggame van makro-fungi, wat op hul beurt weer in staat is om die meer weerstandbiedende polimere in hout te benut. Dit is voorheen bekendgemaak dat daar 'n toename plaasvind in die tempo van houtafbraak deur sekere witvrot-fungi wanneer dit in ko-kulture met geselekteerde gisspesies voorkom. 'n Bekende bewoner van verrottende bome is die wit-vrotfungus Pycnoporus sanguineus. Dit is gevind dat hierdie fungus tot selektiewe delignifikasie in staat is terwyl dit op die hout van populierbome groei, terwyl ander outeurs 'n gelyktydige patroon van delignifisering op Eucalyptus grandis bome gevind het. In laasgenoemde geval is sellulose en lignien gelyktydig afgebreek. Ons was geïnteresseerd in die effek van giste op die oppervlak van vrugliggame van P. sanguineus, en die pionierfungus Aspergillus flavipes, op die houtafbraak deur hierdie wit-vrotfungus. Restriction Fragment Length Polymorphisms (RFLP) analises is gevolglik gebruik om 'n aanduiding te kry van die spesiesamestelling van die kweekbare gisgemeenskap wat met die vrugliggame van P. sanguineus geassosieer word. Die impak van die mees dominante van hierdie gisspesies, naamlik Pichia guilliermondii en Rhodotorula glutinis, asook A. flavipes, op houtafbraak deur P. sanguineus is voorts bepaal deur die analise van die belangrikste houtkomponente na die kweek van ko-kulture op E. grandis houtskyfies wat met warm water gewas is. Ko-kulture van P. sanguineus met die ander fungi is voorberei deur die houtskyfies in vaste fase bioreaktore, aangevul met melasse en ureum, te inokuleer met 'n toepaslike volume van die fungus inokulum om 'n aanvanklike voginhoud van 60% te verkry. Na twee weke se inkubasie by 30°C met konstante belugting is die skyfies ge-oes. Standaard protokol (TAPPI Standard Methods), algemeen deur die papier en pulpindustrie gebruik, is ingespan om die persentasie sellulose, Klason Lignien, asook polêre en oplosmiddel-gedraagde ekstrakte in die skyfies te bepaal. Die gevolglike data is geanaliseer deur gebruik te maak van box plots en biplots. Daar is geen afbraak van Klason Lignien bespeur nie, terwyl die persentasie sellulose wel toegeneem het tydens fungus degradasie. Met die inherente tekortkominge van die Klason Lignien bepaling inaggenome, het die resultate die bevindings ondersteun van andere wat getoon het dat P. sanguineus 'n gelyktydige delignifikasiepatroon openbaar terwyl dit op E. grandis hout groei. Daarby is dit gevind dat die giste geen beduidende rol in die afbraakvermoeë van P. sanguineus gespeel het nie, terwyl A. flavipes 'n antagonisiese effek ten opsigte van die sellulose degradering van P. sanguineus getoon het. Dit was egter duidelik dat die analitiese metodes wat in hierdie studie gebruik is, onvoldoende was om die degradering van hout akkuraat te bepaal. Daarby was dit duidelik dat die metodes nie tussen fungus biomassa en houtkomponente kon onderskei nie. Nogtans het die metodes 'n vingerafdruk verskaf van elke kultuur wat op E. grandis hout groei, wat ons toegelaat het om die chemiese samestelling van die verskillende kulture en die ongeïnokuleerde, met warm water gewasde houtskyfies te vergelyk. Die vraag het gevolglik ontstaan of die effek van 'n bepaalde ko-kultuur op die chemiese samestelling van hout van boomspesie tot boomspesie verskil. Gevolglik is die chemiese wisselinge in verskillende boomspesies, geïnduseer deur 'n P. sanguineus / A. flavipes ko-kultuur, in die volgende gedeelte van die studie ondersoek. Houtskyfies van vier boomspesies, naamlik Acacia mearnsii, Eucalyptus dunnii, E. grandis, en Eucalyptus macarthurii, is met hierdie ko-kultuur geïnokuleer. Die kultuurkondisies en daaropvolgende analises van die houtkomponente was dieselfde as in die eerste deel van die studie. Van die box- en biplots wat van die resultate getrek is, is dit duidelik dat die chemiese samestelling van elke boomspesie op 'n verskillende manier deur die ko-kulture verander is. Lignien-inhoud het ’n waarskynlike toename getoon in A. mearnsii, terwyl E. dunnii 'n afname in sellulose-inhoud getoon het. Die resultate toon dat hout van verskillende boomspesies op verskillende maniere afgebreek word en dat hierdie fenomeen in aanmerking geneem moet word wanneer fungi vir bioverpulping geselekteer word.

This research assessed the influence of hydrologic gradients on woody debris dynamics in a Cumberland Plateau watershed, eastern Kentucky, U.S.A. Although the breakdown of wood can be attributed to several different processes, including leaching, biological decay, fragmentation, and transport, the influence of differing flow regimes has been unstudied. The objectives of this study were to examine how stream channel type (temporary vs. perennial) affected wood processing dynamics (i.e., mass loss and macroinvertebrate colonization and standing stock patterns). Two questions were addressed: (1) do mass loss rates of wood differ across hydrological gradients in stream channels?, and (2) do macroinvertebrate colonization and standing stock patterns vary in relation to hydrologic gradients? Although within each channel type both dry mass and ash free dry mass loss followed a negative exponential model (p < 0.05), there wasn’t a significant between-channel difference in mass loss rates (p > 0.05). Breakdown rates (-k) ranged from 0.133 – 0.194year-1 for perennial streams compared to 0.103 – 0.170year-1 in the temporary streams. Collector-gathers comprised the greatest proportion of macroinvertebrates, accounting for 65.5% (temporary) and 59.3% (perennial) of all taxa colonizing wood bundles, followed by shredders (16.1%, 16.8%), predators (16.8%, 20.1%), (scrapers < 0.1% in both reaches) and filtering collectors (1.2%, 3.7%). Overall, there were no significant between-channel differences for total macroinvertebrate abundance, total macroinvertebrate biomass, and similarly for abundance and biomass of all functional groups. There was a trend, however, of decreasing density and biomass over time of collector-gathers and shredders on wood. Overall, hydrological gradients had no effects on short-term breakdown rates of woody debris or macroinvertebrate colonization patterns. Studies of wood breakdown have been shown to require long study periods (≥ 5 years), therefore, future studies of hydrological gradient may show differing results for woody debris breakdown.