The increasing concern for sustainability and progress of medical research has resulted in the emergence of a wide range of biopolymers. The biodegradability of these alternative biopolymers requires investigation prior to their application in environmental and medical systems. This Thesis describes biodegradation of poly(3-hydroxybutyrate) (PHB), poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (P(HB-co-HV)), poly(3- hydroxyoctanoate) (PHO), poly-DL-lactide (PDLL), poly-DL-lactide-co-glycolide (PDLLG) and ethyl cellulose (EC). Polymers were buried in garden soil for in vivo biodegradation experiments and a mixed population of microbes from the soil were incubated in laboratory in vitro biodegradation experiments. In both systems the short chain length PHA???s degraded rapidly and the medium chain length PHAs and other biomaterials displayed either slow or negligible weight loss. PHB and P(HB-co-HV) copolymers degraded to T50 6.7 to 9.7 times faster in vitro than in vivo. After 380 days burial in soil PHO had lost 60 % of the original 20 mg weight, PDLL 28 % and PDLLG 35 %. Ethyl cellulose and polystyrene did not biodegrade, Polymer-microbe surface interactions were investigated. The faster degrading polymers PHB and P(HB-co-HV) attracted a higher coverage of biofilm than the slower degrading polymers PHO, PDLL and PDLLG for both the in vitro and in vivo experiments. The non-degradable polymers (EC and polystyrene) attracted no biofilm. In vitro and in vivo experiments demonstrated a positive correlation between biofilm coverage and polymer weight loss. Additionally the rougher air sides of solvent cast films attracted more biofilm than the smoother dish sides. Polymer surface changes were quantified with microscopy. Surface roughness of PHB, P(HB-co-8HV) and PHO increased during biodegradation, primarily due to an increase in the waviness component for both in vitro and in vivo degradation. In vitro methods provided a rapid mechanism for protocol development and sufficiently predicted both surface roughness changes and biofilm-biodegradation relationships in vivo. PHB and P(HB-co-8HV) were blended with the biodegradable antifouling agent 4,5-dichloro-2-n-octyl-4-isothiazolin-3-one (DCOI or Sea Nine 211). DCOI leached slowly from the films into the soil delaying biodegradation of the films until a lower residual level of DCOI remained. Biofouling was reduced on PHA films containing DCOI.

The increasing concern for sustainability and progress of medical research has resulted in the emergence of a wide range of biopolymers. The biodegradability of these alternative biopolymers requires investigation prior to their application in environmental and medical systems. This Thesis describes biodegradation of poly(3-hydroxybutyrate) (PHB), poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (P(HB-co-HV)), poly(3- hydroxyoctanoate) (PHO), poly-DL-lactide (PDLL), poly-DL-lactide-co-glycolide (PDLLG) and ethyl cellulose (EC). Polymers were buried in garden soil for in vivo biodegradation experiments and a mixed population of microbes from the soil were incubated in laboratory in vitro biodegradation experiments. In both systems the short chain length PHA???s degraded rapidly and the medium chain length PHAs and other biomaterials displayed either slow or negligible weight loss. PHB and P(HB-co-HV) copolymers degraded to T50 6.7 to 9.7 times faster in vitro than in vivo. After 380 days burial in soil PHO had lost 60 % of the original 20 mg weight, PDLL 28 % and PDLLG 35 %. Ethyl cellulose and polystyrene did not biodegrade, Polymer-microbe surface interactions were investigated. The faster degrading polymers PHB and P(HB-co-HV) attracted a higher coverage of biofilm than the slower degrading polymers PHO, PDLL and PDLLG for both the in vitro and in vivo experiments. The non-degradable polymers (EC and polystyrene) attracted no biofilm. In vitro and in vivo experiments demonstrated a positive correlation between biofilm coverage and polymer weight loss. Additionally the rougher air sides of solvent cast films attracted more biofilm than the smoother dish sides. Polymer surface changes were quantified with microscopy. Surface roughness of PHB, P(HB-co-8HV) and PHO increased during biodegradation, primarily due to an increase in the waviness component for both in vitro and in vivo degradation. In vitro methods provided a rapid mechanism for protocol development and sufficiently predicted both surface roughness changes and biofilm-biodegradation relationships in vivo. PHB and P(HB-co-8HV) were blended with the biodegradable antifouling agent 4,5-dichloro-2-n-octyl-4-isothiazolin-3-one (DCOI or Sea Nine 211). DCOI leached slowly from the films into the soil delaying biodegradation of the films until a lower residual level of DCOI remained. Biofouling was reduced on PHA films containing DCOI.

Lignin is the second most abundant biopolymer on Earth. It is an amorphous, cross-linked, aromatic polymer composed of phenylpropanoid units. There has been an ever growing interest in the biodegradation of this complex polymer for the last 30 years. White-rot fungi have been found to be an important lignin degraders in the natural environment. With the discovery of two groups of hemoprotein enzymes, lignin peroxidases and manganese(II)-dependent peroxidases, from the lignin degrading culture of a white-rot fungus, Phanerochaete chrysosporium, rapid progress has been made in understanding the mechanism of lignin biodegradation. Synthetic metaUoporphyrins, the iron(III) and manganese(III) complexes of meso-tetra(2,6-dichloro-3-sulfonatophenyl)porphyrin (TDCSPPFeCl and TDCSPPMnCl) and meso-tetra(2,6-dichloro-3-sulfonatophenyl)-B-octachloroporphyrin (Cl₁₆TSPPFeCl and Cl₁₆TSPPMnCl), were used in this study to mimic the functions of the "lignin degrading" enzymes. Factors affecting the catalytic activities of these biomimetic catalysts were studied. TDCSPPFeCl could closely mimic lignin peroxidase in the degradation of a number of lignin model compounds, including veratryl alcohol, B-l, B-O-4, B-5, 5-5' biphenyl, phenylpropane, and phenylpropene model compounds. The reactions catalyzed by TDCSPPFeCl include benzyl alcohol oxidation, C[formula omitted],-C[formula omitted] side chain cleavage, demethoxylation, aromatic ring cleavage, benzylic methylene hydroxylation, and C[formula omitted]-C[formula omitted] double bond hydroxylation (glycol formation). Novel solvent incorporated compounds isolated from the oxidation of veratryl alcohol give insights about the site of attack of substrate cation radical by solvent molecules. The isolation of a solvent incorporated product from the oxidation of a phenylpropene model compound suggests a cation radical mechanism for the oxidation of this lignin substructure. The formation of a number of direct aromatic ring cleavage products during the oxidation of some model compounds supports the previously proposed mechanism of aromatic ring cleavage. TDCSPPFeCl was also able to catalyze the oxidation of environmental pollutants such as pyrene and 2,4,6-trichlorophenol. Veratryl alcohol and manganese(II)-complexes have been suggested to function as redox mediators for lignin biodegradation. Evidence has been provided to demonstrate their mediating power during electrochemical and biomimetic degradation of lignin model compounds. In addition to the mechanistic information obtained, the successful oxidation of the model compounds suggests that metalloporphyrins can be important catalysts for the pulp and paper industry and for pollution control. / Science, Faculty of / Chemistry, Department of / Graduate

For over 50 years, synthetic petrochemical-based plastics have been produced in ever growing volumes globally and since their first commercial introduction; they have been continually developed with regards to quality, colour, durability, and resistance. With some exceptions, such as polyurethanes, most plastics are very stable and are not readily degraded when they enter the ground as waste, taking decades to biodegrade and therefore are major pollutants of terrestrial and marine ecosystems. During the last thirty years, extensive research has been conducted to develop biodegradable plastics as more environmentally benign alternatives to traditional plastic polymers. Polyvinyl alcohol (PVA) is a water-soluble polymer which has recently attracted interest for the manufacture of biodegradable plastic materials. PVA is widely used as a paper coating, in adhesives and films, as a finishing agent in the textile industries and in forming oxygen impermeable films. Consequently, waste-water can contain a considerable amount of PVA and can contaminate the wider environment where the rate of biodegradation is slow. Despite its growing use, relatively little is known about its degradation and in particular the role of fungi in this process. In this study, a number of fungal strains capable of degrading PVA from uncontaminated soil from eight different sites were isolated by enrichment in mineral salts medium containing PVA as a sole carbon source and subsequently identified by sequencing the ITS and 5.8S rDNA region. The most frequently isolated fungal strains were identified as Galactomyces geotrichum, Trichosporon laibachii, Fimetariella rabenhorsti and Fusarium oxysporum. G. geotrichum was shown to grow and utilise PVA as the sole carbon source with a mean doubling time of ca. 6-7 h and was similar on PVA with molecular weight ranges of 13-23 KDa, 30-50 KDa and 85-124 KDa. When solid PVA films were buried in compost, Galactomyces geotrichum was also found to be the principal colonizing fungus at 25°C, whereas at 45°C and 55°C, the principle species recovered was the thermophile Talaromyces emersonii. ESEM revealed that the surface of the PVA films were heavily covered with fungal mycelia and DGGE analysis of the surface mycelium confirmed that the fungi recovered from the surface of the PVA film constituted the majority of the colonising fungi. When PVA was added to soil at 25°C, and in compost at 25°C and 45°C, terminal restriction fragment length polymorphism (T-RFLP) revealed that the fungal community rapidly changed over two weeks with the appearance of novel species, presumably due to selection for degraders, but returned to a population that was similar to the starting population within six weeks, indicating that PVA contamination causes a temporary shift in the fungal community.

This study evaluated the potential of the aerobic Mycobacterium strain JS6O to grow on a variety of organic acid substrates, and the possible effects an organic acid would have on the degradation rate of vinyl chloride (VC). A series of batch growth tests were designed to determine the time it took to consume the substrate and the overall increase in biomass. Strain JS6O was found capable of growth on acetate, propionate, and butyrate, but could not grow on formate or lactate. Acetate was chosen for further study because strain JS6O consumed acetate the most rapidly of all the organic acids tested, and acetate is a common product of fermentation reactions in the subsurface. Strain JS6O was confirmed to grow on both ethylene and vinyl chloride as the sole carbon and energy source. Comparatively, strain JS6O's rate of growth on VC is much slower than that of ethylene. With acetate as an augmenting growth substrate, ethylene and VC utilization rates increased by 30% and 48%, respectively. Since acetate and VC are often found together in contaminated chlorinated ethene plumes, this makes a strong case for natural attenuation of VC by strain JS6O. A series of kinetic tests were implemented to determine the K[subscript s] and k[subscript max] of strain JS6O for ethylene, VC, and c-DCE. The K[subscript s] and k[subscript max] for ethylene determined through NLSR methods was similar to the values published in Coleman et al. (2002), supporting the maintenance of a pure culture throughout the experimental work. When strain JS6O was exposed to the isomers of DCE (trans-1,2-dichloroethylene (t-DCE), cis-1,2-dichloroethylene (c-DCE), and 1,1-dichloroethylene (1,1-DCE)) the cells were unable to grow on these compounds. However, when growing on acetate, strain JS6O cometabolized c-DCE and t-DCE, but not 1,1-DCE, with c-DCE transformed more rapidly than t-DCE. Transformation of c-DCE was also observed with growth on VC and ethylene. The presence of c-DCE was shown to partially inhibit VC degradation, but had no effect on ethylene degradation. The cometabolism results with acetate further indicate that strain JS6O is a good candidate for natural attenuation of multiple chlorinated ethenes in the subsurface. / Graduation date: 2006

Graduation date: 1996

published_or_final_version / abstract / Ecology and Biodiversity / Master / Master of Philosophy

The purpose of the study was to set up an in vitro model of the colon which would permit the analysis of cellulose fermentation by human colonic microflora. Studies of the degradation of polysaccharides by colonic bacteria may help to explain the observed physiological consequences of consuming dietary fiber common in foods. This study resulted in the use of a simple anaerobic batch fermentation system. It is assumed that the bacteria in fresh feces are representative of colonic bacteria. This batch culture system consists of the culture medium, the food fiber and the fecal inoculum. The fecal inoculum is prepared from freshly voided feces from a single individual. The food fiber is prepared from the vegetable/fruit starting material by repeated extraction with 90% ethanol, resulting in an alcohol insoluble residue(AIR). Extents of cellulose fermentation were measured after 4, 8, 12 and 24 hour fermentation periods at 37°C. The cellulose content of the samples before and after fermentation was determined by measuring the glucose yield (glucose oxidase assay) from an acid hydrolysate of the residue remaining after repeated acid detergent extractions. The extent of cellulose fermentation was then estimated by difference. The susceptibility to intestinal fermentation of the cellulose component of acorn squash and red beets was investigated using this model system. The cellulose content of squash and beet AIR was 26.71% ± 0.95% and 23.22% ± 0.89%, respectively. The extent of cellulose of fermentation of squash cellulose after 4, 8, 12 and 24 hrs incubation was 6.04% ± 0.69%, 10.58% ± 2.10%, 17.11% ± 6.37% and 96.18% ± 1.36%, respectively. The extent of fermentation of beet cellulose after 4, 8, 12 and 24 hrs incubation was 17.52% ± 1.83%, 23.52% ± 1.44%, 30.53% ± 4.12% and 96.06% ± 0.39%, respectively. The results indicate that the cellulose component of both vegetables is susceptible to considerable degradation within the human intestinal tract. / Graduation date: 1991

Call number: LD2668 .T4 1986 L437 / Master of Science / Chemical Engineering

No description available.