Plasticizers are ubiquitous environmental contaminants. Biodegradation of some of these chemicals, such as di(2-ethylhexyl) phthalate (DEHP or DOP), has been shown to lead to the accumulation of toxic metabolic breakdown products. As a result there is a desire to produce new, fully biodegradable, "green" plasticizers. With this goal in mind, a series of tests were developed to be used to measure the plasticizing efficiency of potential green plasticizers. The base resin selected for the study was poly(vinyl chloride) (PVC). The glass transition temperature (Tg) of the plasticized polymer was measured by temperature-modulated differential scanning calorimetry (TMDSC). Tensile tests were carried out on samples of the material from which the tensile strength and the strain at break of the material were measured. The aforementionned properties were measured for PVC plasticized with the commercial plasticizers DEHP, diethylene glycol dibenzoate (DEGDB) and dipropylene glycol dibenzoate (DPGDB) at several plasticizer concentrations. / 1,5 pentanediol dibenzoate (PDDB) was synthesized and evaluated as a plasticizer by comparing results for this compound with those for the commercial plasticizers using the developed tests. The depression in Tg and tensile properties were comparable at a fixed composition for blends with PDDB relative to blends with DEHP, DEGDB, and DPGDB. PDDB was subjected to biodegradation unsing co-metabolism by the common soil bacterium Rhodococcus rhodocrous (ATCC 13808). After 16 days of growth, nearly all the PDDB was degraded and only small amounts of transient, unidentified, metabolites were observed in the growth medium during the experiment.

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The extracellular culture supernatants of the white rot fungus Trametes versicolor can bleach and delignify unbleached kraft pulps, however the process is too slow for commercial application. Though at least two oxidative enzymes, laccase and manganese peroxidase (MnP) produced by this organism can catalyze a partial delignification of kraft pulp, the effect observed is small relative to that obtained with the complete fungal system. To develop a synthetic (cell-free) delignification system, other protentially important components of the culture supernatant were identified and their contributions to biobleaching and delignification were evaluated. The presence of pulp did not significantly affect the overall carbon balance of the fungus, but a number of non-volatile metabolites (oxalic, fumaric, glyoxylic and phenyllactic acids) induced by the presence of pulp were identified. In T. versicolor 52J, the secretion of manganese peroxidase (MnP), and cellobiose:quinone oxidoreductase (CBQase) enzymes were inducible by pulp whereas cellulase and laccase were not. Several low molecular weight metabolites secreted by T. versicolor functioned as effective Mn(III) complexing agents at their physiological concentrations and promoted MnP activity. / Two distinct CBQase proteins are secreted by T. versicolor 52J, CBQase 4.2 a a 113kDa homodimer containing both heme and flavin cofactors and CBQase 6.4, a 48 kDa monomer with a flavin cofactor only. Superficially, these enzymes appear very similar to the cellobiose oxidase (CBO) and CBQase reported in Phanerochaete chrysosporium. CBQase 4.2 was shown to reduce insoluble manganese dioxide to its soluble Mn(II) and Mn(III) forms with the concommitant oxidation of cellobiose. The sugar acids formed by CBQase could function as effective complexing agents for Mn(III),and complement the Mn(II) to Mn(III) oxidation activity of MnP. / It is proposed that a redox cycling of lignin molecules by certain fungal oxidative and reductive enzymes occurs during delignification and that this cycling ultimately promotes net lignin degradation. A redox cycle wa established between T. versicolor CBQase and laccase which allowed the O$ sb2$ comsumption rate of laccase to remain at a constant level and the total O$ sb2$ consumption by the enzyme was much treater than if the substrate were incubated with laccase alone. A new assay for CBQase based on the ability of this enzyme to reduce the radical intermediates formed during laccase-mediated chlorpromazine oxidation was developed. A redox cycle for these two enzymes was established using both model substrates like CPZ, and with a kraft lignin preparation. CBQase inhibited the formation of polymeric material by laccase; however no evidence was found indicating that cycling with these two enzymes favors depolymerization of kraft lignin. However, the alkali extractability of residual lignin in kraft pulp was increased by a sequential treatment with MnP followed by CBQase.

AlcellRTMlignin has been used commercially in adhesive preparation and brake pad linings and experimentally in animal feeds to reduce or eliminate diarrheal attacks in farm animals. Our study dealt with elucidating the antibacterial effect of AlcellRTMlignin. It would appear that adsorbance of E. coli cells to AlcellRTMlignin particles is not essential for destruction of the organism. / The antibacterial activity was delayed by the inclusion of Mg 2+ ions in the AlcellRTMlignin filtrate or in the enumeration medium (BHIA). Addition of bile salts to the enumeration medium (BHIA) enhanced the culturability loss of E. coli cells suspended in the filtrate of AlcellRTMlignin. Using FTIR methodology, it appears, that compounds of AlcellRTMlignin affect phospholipid-phospholipid and/or phospholipid-protein interactions in bacterial membranes, causing the patching of membrane phospholipids and proteins. / Additional studies are necessary to evaluate interactions of compounds of AlcellRTMlignin with bacterial cells.

Two strains of Alcaligenes denitrificans, designated BRI 3010 and BRI 6011, were isolated from polychlorinated biphenyl (PCB) contaminated soil using 2,5-dichlorobenzoic acid (2,5-DCBA) and 2,4-DCBA, respectively, as sole carbon and energy sources. Both strains degraded 2-chlorobenzoic acid (2-CBA), 2,3-DCBA, and 2,5-DCBA. BRI 6011 alone degraded 2,4-DCBA. Metabolism of the chlorinated substrates resulted in the stoichiometric release of chloride, and degradation proceeded by intradiol cleavage of the aromatic ring. Growth of both strains on dichlorobenzoic acids induced pyrocatechase activities having catechol (catechol 1,2-dioxygenase) and chlorocatechols (chlorocatechol 1,2-dioxygenase) as substrates. Growth on 2-CBA and benzoic acid induced a pyrocatechase activity (catechol 1,2-dioxygenase) directed against catechol only. / The chlorocatechol 1,2-dioxygenase from BRI 6011 was purified, characterized, and compared with the chlorocatechol 1,2-dioxygenase from Pseudomonas sp. B13 and P. putida, organisms limited with respect to their CBA degradative versatility. These enzymes appear to be very similar based on biochemical and genetic data and possess sufficient broad substrate specificity to accommodate a wide range of chlorinated catechols, hence the increased versatility for chlorobenzoic acid degradation of A. denitrificans cannot be attributed to a more specialized chlorocatechol 1,2-dioxygenase. / Uptake of benzoic acid by BRI 3010 and BRI 6011 was inducible, exhibited saturation kinetics and the substrate was accumulated intracellularly against a concentration gradient by a factor of 8 and 10, respectively, indicative of active transport. Uptake of 2,4-DCBA by BRI 6011 was constitutive and saturation kinetics were not observed, suggesting passive diffusion of 2,4-DCBA and other CBAs into the cell down a concentration gradient. / Based on oxygen uptake experiments with whole cells, benzoic acid dioxygenase and chlorobenzoic acid dioxygenase activity was induced by benzoic acid and ortho-substituted chlorobenzoic acids, respectively. Since 2,4-DCBA diffuses across the membrane and the expected catecholic intermediates of 2,4-DCBA metabolism are metabolizable by BRI 3010, this suggests that the major difference between BRI 3010 and BRI 6011 might be the inability of the chlorobenzoic acid dioxygenase in BRI 3010 to recognize 2,4-DCBA as a substrate.

An in-depth study of the biodeterioration of the Hulett Aluminium hot roll mill emulsion, Prosol, was conducted. Samples of the emulsion in use at the hot roll mill were taken from various areas of the emulsion reticulation system in order to identify regions of highest microbial contamination. Standard plate count techniques and diagnostic procedures were employed to quantify and identify the microorganisms in these samples. In some of the highly contaminated areas of the emulsion reticulation system, microorganisms exceeded lxlO'CFUml'1 emulsion. A range of bacteria was identified which included members of the genera: Bacillus; Pseudomonas; Escherichia; Enterobacter; Sporosarcina; Micrococcus; Aeromonas; Chromobacterium and Desulfovibrio. Various fungi, including several yeasts, were also isolated and some of the filamentous spore-forming types were identified zsAspergillus spp.; Penicillium spp. and a Cladosporium sp. A visual scale was developed to assess the growth rate of the isolated microorganisms on a range of specific media containing various emulsion components as carbon and energy source. Although the results obtained by using this scale were not conclusive, a few biodegradable components were nonetheless identified. It was found that mixed cultures of the above microorganisms had a greater biodeteriorative effect on the emulsion than did any of the pure cultures when applied separately. This suggested complex microbial interactions were involved in the breakdown of the emulsion. A laboratory-scale model system representative of the Hulett Aluminium hot roll mill was designed and constructed to carry out a series of tests on unprotected and biocide-treated emulsions. A range of biocide concentrations were tested from which the minimum biocide inhibitory concentration was calculated. It was shown that microorganisms exposed to sublethal doses of the biocide Busan (active component glutaraldehyde) over a prolonged period of time, exhibited greater levels of tolerance and resistance to the biocide than did those microorganisms not previously exposed. It was deduced that less frequent, shock doses of biocide are more effective in the control and eradication of emulsion degrading microorganisms than are frequent, low level doses of the same biocide. In addition to the biocide studies, three imported so-called 'biostable' emulsions were evaluated as possible replacements for the susceptible Prosol. Of these three imported emulsions, two viz. HRF3 and Houghton Biostable were shown to be more resistant than Prosol to biodeterioration. After assessing the current hot roll mill management practices, a number of recommendations were made, including: the improvement of plant hygiene; education of the mill workers; improvement of emulsion monitoring; improvement of down-time management and improvement of biocide dosing regimes. Recommendations are also made for minimizing potential microbial growth in the new hot roll mill currently under construction at the Hulett Aluminium processing plant at Pietermaritzburg, South Africa. / Thesis (M.Sc.)-University of Natal, Pietermaritzburg, 1998.

1,2-Dichloroethane (1,2-DCA), a highly toxic and recalcitrant compound, is produced anthropogenically in larger quantities than any other chlorinated compound. It is regarded as a mutagen and carcinogen, thus making it a priority target molecule for biological degradation. In addition, the intermediates of 1,2-DCA degradation are highly reactive and toxic, due to the electrophilic nature of the carbonyl groups in these compounds. Aerobic biodegradation of 1,2-DCA, resulting in complete mineralization, has previously been reported in Xanthobacter autotrophicus GJ10 and some Ancylobacter aquaticus strains. X. autotrophicus GJ10 has been found to possess chloroacetaldehyde (CAA) dehydrogenase and haloacid (HA) dehalogenase enzymes, both of which play a crucial role in 1,2-DCA degradation. Five strains of Ancylobacter aquaticus capable of utilizing 1,2-DCA as a sole carbon and energy source have recently been isolated in our laboratory. The degradation potential and specific dehalogenase activities of these bacterial isolates against 1,2-DCA and other halogenated compounds as a carbon source were investigated and compared to previously characterized organisms, viz., X. autotrophicus GJ10 and Ancylobacter aquaticus strains AD25 and AD27. Furthermore, this study proposed to detect the presence of the CAA dehydrogenase (aldB) and HA dehalogenase (dhlB) encoding genes in these isolates. Growth of all strains in the presence of 1,2-DCA as a carbon source was monitored over an 84 h period, in minimal medium supplemented with either vitamins or yeast extract. Dehalogenase activities were measured colorimetrically by monitoring halide release by crude cell extracts of the isolates. In order to detect the presence of dhlB and aldB genes, genomic DNA of the isolates was digested with individual restriction endonucleases, viz., EcoRI, PstI, HindIII and BamHI, and then subjected to Southern hybridization experiments. All isolates demonstrated significant growth rates in both vitamin and yeast extract supplemented media, with the former having a greater overall growth effect. Ancylobacter aquaticus DH5 demonstrated the highest growth rate of 0.147.h-1 in the presence of vitamins while Ancylobacter aquaticus DH12 displayed the highest growth rate of 0.118.h-1 with yeast extract. Optimum haloalkane dehalogenase activities of these bacterial isolates were confirmed at pH 8, similar to the activity in X. autotrophicus GJ10, while haloaciddehalogenase activity had a broader pH range. Hydrolytic dehalogenase activity of the bacterial isolates using a range of halogenated aliphatic compounds was also determined. Results demonstrated a wide substrate range with activity being observed on 1,3- dibromopropane, 1,2-dibromoethane and 1,3-dichoropropene, for all isolates. Southern Hybridization experiments confirmed the presence of both aldB and dhlB genes in X. autotrophicus GJ10. The dhlB probe produced a positive signal for an EcoRI fragment in Ancylobacter aquaticus DH12 while the aldB probe hybridized and produced a single positive signal on similar sized PstI fragments for all organisms except A. aquaticus AD25 which produced two positive signals. The results in this study demonstrate the potential application of the newly isolated strains of Ancylobacter aquaticus. in future bioremediation strategies. The detection of the genes involved in 1,2-DCA degradation further support the use of these isolates and/or their enzymes for the degradation of 1,2- DCA as well as other halogenated compounds. Future work need to determine sequence similarity of these genes detected in A. aquaticus strains to the genes in Xanthobacter autotrophicus GJ10 and other previously reported genes. It may also be important to investigate the activity of the enzymes under various environmental conditions and to determine enzyme structure and the catalytic sites, so as to gain knowledge of their degradation potential on site. Characterization of enzymes at both the molecular and protein levels may be necessary and beneficial for implementation in strategies involving bioremediation for the biological degradation of a wide range of halogenated aliphatic hydrocarbons. / Thesis (M.Sc.)-University of KwaZulu-Natal, Westville, 2011.

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