Thesis (MSc)--Stellenbosch University, 2005. / ENGLISH ABSTRACT: This study describes: I. The cloning of the CVP 19 gene and construction of the intracellular expression vector pPIC3.5K-CYP19. II. The transformation of the yeast, Pichia pastoris with the constructed vector. III. The expression ofP450arom in Pichia pastoris. IV. The determination of enzyme activity and isolation of the protein from the Pichia pastoris cells. V. The expression of P450c 17 in Pichia pastoris. VI. The determination of kinetic constants for the conversion of progesterone to 170H-progesterone and 160H-progesterone by P450c17. / AFRIKAANSE OPSOMMING: Hierdie studie beskryf: I. Die klonering van die CVP 19 geen en die konstruksie van die intrasellulêre uitdrukkingsplasmied, pPIC3.5K-CYPI9. II. Die transformasie van die gis, Pichia pastoris, met die gekonstrueerde plasmied. III. Die uitdrukking van aromatase in Pichia pastoris. IV. Die bepaling van ensiemaktiwiteit en die isolering van die proteïen vanuit Pichia pastoris. V. Die uitdrukking van P450c17 in Pichia pastoris. VI. Die bepaling van kinetiese konstantes vir die omsetting van progesteroon na 170H-progesteroon en 160H-progesteroon deur P450c17.

We can now manipulate the genetic material of living organism routinely and cheaply. This has inspired a burgeoning field of synthesis based on DNA as a building block. The development of this new synthetic field has mirrored the trajectory of synthetic organic chemistry from small molecular systems to complex macromolecular assemblies. At first, this field of synthetic biology delivered recombinant proteins that enhanced our understanding of the structure-function relationship of biological macromolecules. Now, as the synthetic tools and analysis methods have come of age, synthetic whole-cell and multicellular systems have come within reach. In Chapter 1 we review the significant advances in DNA synthesis and analysis that have brought us to this point. In this work, we first ask what practical applications will benefit most from the unique qualities of synthetic whole-cell system, such as their ability to replicate, sense and respond with molecular specificity. In Chapter 2, we implement a pathogen detection platform based solely on genetically modified yeast. This approach holds the potential to deliver ultra low-cost sensors that can be used and produced at the point-of-care. In Chapter 3, we develop methods to target these yeast-based sensors for the detection of any peptide biomarker of choice. We next look forward to the potential of synthetic multicellular systems. While natural multicellular systems can be directly manipulated, our ability to rationally build multicellular systems from the bottom-up is still in its infancy. There still remain gaps in the available tools to make and analyze such synthetic systems. In Chapter 4, we leverage the explosion of available genomic databases to uncover a highly extensible set of cell-cell signaling modules. In Chapter 5, we implement ratiometric fluorescent tags to track mixed cell populations in multiplex. Together these components will be useful in implementing and analyzing synthetic communication networks that will be key components of advanced synthetic multicellular systems.

Title from title page of PDF (University of Missouri--St. Louis, viewed February 22, 2010). Includes bibliographical references.

Submitted in fulfillment for the requirement of a Degree of Master of Technology: Biotechnology, in the Department of Biotechnology and Food Technology, Faculty of Applied Sciences, Durban University of Technology, Durban, South Africa, 2009. / Protein engineering has provided a key for adapting naturally-occurring enzymes for industrial processes. However, several obstacles have to be overcome after these proteins have been adapted, the main one being finding a suitable host to over-express these recombinant protein. This study investigated Saccharomyces cerevisiae, Pichia pastoris and Escherichia coli as suitable expression hosts for a previously modified fungal xylanase, which is naturally produced by the filamentous fungus, Thermomyces lanuginosus. A xylanase variant, NC38, that was made alkaline-stable using directed evolution was cloned into four different vectors: pDLG1 with an ADH2 promoter and pJC1 with a PGK promoter for expression in S. Cerevisiae, pBGP1 with a GAP promoter for expression in P. pastoris and pET22b(+) for expression in E. Coli BL21 (DE3). S. Cerevisiae clones with the p DLG1-NC38 combination showed very low activity on the plate assay and were not used for expression in liquid media as the promoter was easily repressed by reducing sugars used during production experiments. S. cerevisiae clones carrying pJC1-NC38 were grown in media without uracil while P. Pastoris clones were grown in YPD containing the antibiotic, zeocin and E. Coli clones were grown in LB with ampicillin. The levels of xylanase expression were then compared between P. Pastoris, S. cerevisiae and E. coli. The highest recombinant xylanase expression was observed in P. Pastoris with 261.7U/ml, followed by E.coli with 47.9 U/ml and lastly S. cerevisiae with 13.2 U/ml. The localization of the enzyme was also determined. In the methylotrophic yeast, P. Pastoris, the enzyme was secreted into the culture media with little or no contamination from the host proteins, while the in other hosts, the xylanase was located intracellularly. Therefore in this study, a mutated alkaline stable xylanase was successfully expressed in P. Pastoris and was also secreted into the culture medium with little or no contamination by host proteins, which favours the application of this enzyme in the pulp and paper industry.

Submitted in complete fulfillment for the Degree of Master of Technology (Biotechnology)in the Department of Biotechnology and Food Technology, Faculty of Applied Sciences, Durban University of Technology, Durban, South Africa, 2009. / Protein engineering has been a valuable tool in creating enzyme variants that are capable of withstanding the extreme environments of industrial processes. Xylanases are a family of hemicellulolytic enzymes that are used in the biobleaching of pulp. Using directed evolution, a thermostable and alkaline stabl xylanase variant (S340) was created from the thermophilic fungus, Thermomyces lanuginosus. However, a host that was capable of rapid growth and high-level expression of the enzyme in large amounts was required. The insert containing the xylanase gene was cloned into a series a pET vectors in Escherichia coli BL21 (DE3) pLysS and trimmed from 786 bp to 692 bp to remove excess fungal DNA upstream and downstream of the open reading frame (ORF). The gene was then re-inserted back into the pET vectors. Using optimized growth conditions and lactose induction, a 14.9% increase in xylanase activity from 784.3 nkat/ml to 921.8 nkat/ml was recorded in one of the clones. The increase in expression was most probably due to the removal of fungal DNA between the vector promoter and the start codon. The distribution of the xylanase in the extracellular, periplasmic and cytoplasmic fractions was 17.3%, 51.3% and 31.4%, respectively. The modified enzyme was then purified to electrophoretic homogeneity using affinity chromatography. The xylanase had optimal activity at pH 5.5 and 70°C. After 120 min at 90°C and pH 10, S340 still displayed 39% residual activity. This enzyme is therefore well suited for its application in the pulp and paper industry.

This thesis presents a systematic investigation ofyeasts associated with wine grapes cultivated in several Australian vineyards during the 2001-2003 vintages. Using a combination of cultural and molecular methods, yeast populations of red (Cabernet sauvignon, Merlot, Tyrian) and white (Sauvignon blanc, Semilion) grape varieties were examined throughout grape cultivation. The yeast-like fungus, Aureobasidium pullulans, was the most prevalent species found on grapes. Various species of Cryptococcus, Rhodotorula and Sporobolomyces were frequently isolated throughout grape maturation. Ripe grapes showed an increased incidence of Hanseniaspora and Metschnikowia species for the 2001-2002 seasons, but not for the drought affected, 2002-2003 seasons. Atypical, hot and dry conditions may account for this difference in yeast flora and have limited comparisons of data to determine the influences of vineyard location, grape variety and pesticide applications on the yeast ecology. More systematic and controlled studies of these variables are required. Damaged grape berries harboured higher yeast populations and species diversity than intact healthy berries. PCR-DGGE analysis was less sensitive than plate culture for describing the diversity of yeast species on grapes; it detected prevalent species, but subdominant populations below 103 CFU/g were not detected. In some cases, PCR-DGGE revealed the presence ofyeasts (Candida galli, C. zemplinina) not isolated by culture. Fermentative wine species (Kluyveromyces, Torulaspora, Saccharomyces) were rarely isolated, and only detected by enrichment cultures. Significant morphological and genetic variability were detected among A. pullulans and other black yeasts isolates from grapes. Taxonomic characterization of 61 strains by ITS-RFLP and rDNA sequencing revealed that they belonged to several distinct species within the generic groupings ofAureobasidium, Hormonema and Kabatiella. Isolates were strong producers of extracellular enzymes and polysaccharides that could have oenological significance, and, using a plate assay, some were antagonistic towards Bacillus thuringiensis, several wine yeasts, and some spoilage and mycotoxigenic fungi found on grapes. Growth of Saccharomyces cerevisiae was not inhibited by these organisms in grape juice. A species-specific probe was developed for the identification of the wine spoilage yeast, Zygosaccharomyces bailii in a microtitre plate hybridization assay. The probe detected 102 cells/ml in wine, reliably differentiating Z. bailii from other Zygosaccharomyces and other wine-related yeasts.

Thesis (Ph. D.)--University of Washington, 2007. / Vita. Includes bibliographical references (p. 161-186).

Thesis (M.S.)--Duquesne University, 2004. / Title from document title page. Abstract included in electronic submission form. Includes bibliographical references (p. 76-88) and abstract.

Thesis (Ph.D.) - Carleton University, 2007. / Includes bibliographical references (p. 129-156). Also available in electronic format on the Internet.

Thesis (M.S.)--Mississippi State University. Department of Biological Sciences. / Title from title screen. Includes bibliographical references.