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No description available.

The effect of the key physiological parameters on the production of solvents in the acetone-butanol fermentation using the anaerobic bacterium Clostridium acetobutylicum was examined in this work. / The theoretical solvent yield was calculated based on expressing stoichiometric relationships between the substrate and the products of the process. The maximum theoretical yield under the acceptable process conditions was established ranging from 38.6% to 39.9%. / A linear correlation was established between the production of solvents and gases which varied with the mixing rate of the fermentation system. / Elevated hydrogen partial pressure affected the metabolism of C. acetobutylicum resulting in increased butanol and ethanol yields (based on glucose) by an average of 18% and 13%, respectively. / A mathematical model for the batch acetone-butanol fermentation was formulated using original experimental data for the microbial growth, sugar consumption and metabolite biosynthesis. This model was used for computer process simulations. Parametric sensitivity analysis indicated the importance of the key process parameters. / A method of systems analysis was applied in analysing pronounced physiological differences in the performance of one of the C. acetobutylicum culture strains. The cellular transport mechanism for substrate (glucose), solvents and acids through the cell membrane was established to depend on its permeability and the number of sugar transport "sites". Experimental results obtained from the study of the uptake of 3-0-methyl glucose (0.7mM) by the "normal culture" and the "retarded culture" confirmed the theoretical predictions of a slower transpost in the "retarded culture". The theoretical predictions were further confirmed by additional experimental results. / A mathematical "Physiological State Model" was developed which includes the culture physiological parameters as well as the internal and the external culture conditions. Using this mathematical model the standard and the substandard acetone-butanol fermentations could be simulated. / These results demonstrate the application of the method of systems analysis in elucidation of the role played by the key culture physiological parameters in the fermentation process.

Typescript. / Thesis (Ph. D.)--University of Hawaii, 1966. / Bibliography: leaves 76-79. / xii, 88 l mounted illus., tables

Clostridium difficile is an important hospital-acquired pathogen causing C. difficile-associated diarrhoea (CDAD) in patients exposed to antibiotics. The lack of information on bacteriophages of C. difficile, and the potential of phages as therapeutic agents for the treatment of CDAD, prompted the isolation and characterisation of phages active against clinical isolates of C. difficile in order to determine the prevalence and significance of phages of this anaerobe. Three (5.4 %) of 56 clinical C. difficile isolates induced by mitomycin C yielded dsDNA phages C2, C5, C6 and C8. The four phages differed from previously described C. difficile phages in particle morphology, burst size and host range. C2, C5 and C8 particles were members of the family Myoviridae, while C6 belonged to Siphoviridae. The burst sizes were 5 for C2, 7 for C5, 19 for C6 and 33 for C8. C8 had the broadest host range, lysing 27 out of 56 (48 %) C. difficile isolates, followed by C6 (43 %), C5 (20 %) and C2 (20 %). Superinfection experiments, restriction enzyme analysis and Southern hybridisation showed C2 and C5 to be closely related with C8 somewhat related to them, however, C6 was distantly related to the other three phages. C2 was further characterised as a representative phage. Its genome did not possess cohesive ends, and was shown to integrate chromosomally via an attP site identified within a 1.9 kb HindIII fragment. However, an integrase gene, which is typically close to the attP region, was not located. Nine of 16 HindIII fragments of C2, including the 1.9 kb fragment, were cloned into pUC18. Approximately 9 kb of the estimated 43 kb genome of C2 was sequenced and analysed. Seven of the nine translated sequences were homologous to phage structural proteins, two sequences were not homologous to any relevant protein in the Genbank and EMBL databases, and one was homologous to proteins of Clostridium species. Nucleotide homology between the C2 sequences and the recently sequenced C. difficile strain CD630 was found in three regions within CD630 genome. Seven of the nine sequences, including the 1.9 kb fragment, were clustered in one region. These data suggest that the genes constitute a phage structural gene module. The presence of C2-like sequences in CD630, and Southern hybridisation of C. difficile strains using phage probes, suggested related prophage sequences may be commonly present in this bacterial species. An investigation was carried out to determine the presence of toxin genes tcdA and tcdB, and PaLoc-associated gene tcdE, in phage DNA. In addition, the effect of phage infection on toxin production of toxigenic C. difficile strains was studied. Of the three genes, tcdE only was detected in phages C2, C5 and C8, but not in C6. Strains that maintained phages in a stable manner (lysogens) were isolated and used in toxin studies. The amount of toxin B produced was measured by cytotoxic assays using Vero cells, and toxin A production was measured by ELISA. Although phages did not encode toxin A or B genes, there was a significant increase in toxin B production in some lysogens. There was no increase in toxin A production. Transcriptional analyses of tcdA and tcdB in lysogens and parental strains was performed by real-time RT-PCR and Northern hybridisation to determine whether phage was affecting regulation of toxin transcription. Phage did not appear to affect toxin gene transcription, although results from real-time RT-PCR and Northern hybridisation were conflicting. A phage induced from the highly toxigenic reference strain VPI 10463 was also briefly characterised and investigated for its effect on toxin production in VPI 10463. The phage, ΦCV, had similar particle morphology to C2, C5 and C8, and had some HindIII bands in common with C2 and C5. Two cured variant strains produced significantly less toxin B compared to VPI 10463. In conclusion, several important properties of C. difficile phages were characterised. It appears these temperate phages may play a role in toxin production making them unsuitable as therapeutic agents for the treatment of CDAD. However, C2 phage may have potential as the basis for an integrative vector that will add to the genetic tools available for clostridia.

Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1988. / Vita. Abstract. Includes bibliographical references (leaves 88-100). Also available via the Internet.

Thesis (Ph.D.)--University of Western Australia, 2004.

Ulm, Univ. Diss., 2006.

Ulm, Univ. Diss., 2006.

Thesis (M.Eng.). / Written for the Dept. of Chemical Engineering. Title from title page of PDF (viewed 2008/04/12). Includes bibliographical references.