Thesis (Ph.D.)--University of Delaware, 2005. / Principal faculty advisor: Anne S. Robinson, Dept. of Chemical Engineering. Includes bibliographical references.

A three part study was carried out to examine rheological, colloidal and floe microstructural aspects of industrial brewing yeast strains. Following a review of the literature, the rheological properties of four yeast strains (two flocculent ale and lager types and their non-flocculent variants) were examined. In related colloidal studies, orthokinetic flocculation rates of these strains as well as their cell surface charge were determined. Floc microstructure was characterized using both light and scanning electron microscopy. In a summary chapter, the cell floc model (a modification of Hunter's elastic floc model) was used to the explain the rheological and colloidal behaviour of brewing yeast suspensions. Flow behaviour studies of the commercial yeast suspensions suspended in a calcium-containing sodium acetate buffer revealed that yeast flocculent characteristics had an important influence on their suspension flow behaviour. As cell concentrations increased, suspension flow properties become increasingly non-Newtonian and could be described by the Casson model at low rates of shear and the Bingham model at shear rates above 100 s⁻¹. The cell floc model was proposed to explain the Bingham flow behaviour of these csuspensions. The Bingham yield stress in these suspensions was believed to be a function of the orthokinetic capture coefficient, cell volume and the energy to break up doublet cells. Increasing temperature tended to lower the Bingham yield stress in lager strains and increase the yield stress in ale strains. A semi-empirical explanation for the viscosity increase of deflocculated cell suspensions and the estimation of pseudo-capture coefficients was presented. Furthermore, studies of the flow behaviour of yeast strains suspended in decarbonated ale and lager beer revealed that: 1) suspensions of flocculent strains show higher yield stress values than their non-flocculent variants, 2) ale strain suspensions tended to have higher yield values than the lager strains and 3) yeast dispersed in beer had higher yield stress values than when suspended in buffered calcium suspensions. This last observation was believed to reflect the influence of ethanol on the cell binding process which has important implications for future measurements of yeast flocculation. Colloidal studies revealed for the first time, that the orthokinetic rate of flocculation of brewing yeast cells could be modelled by a first order equation, as predicted by fundamental colloid theory. While subject to considerable variation, measured rate constants led to the calculation of orthokinetic capture coefficients. Yeast cell zeta potential values generally agreed with literature data but could not be employed in the DLVO model of colloid flocculation to explain measured orthokinetic capture coefficient values. Examination of the cell zeta potential data indicated that the data had non-normal distributions. SEM examination of the four industrial yeast strains suggested that a number of distinct structures mediated cell-to-cell interaction and that intra-strain differences occurred. These findings, along with the observation of non-normal surface charge distributions, indicated that these industrially pure strains had undergone substantial variation. Treatment of the flocculent cells with pronase tended to reduce cell-to-cell contacts. In the summary chapter the cell floe model was employed to describe the rheological behaviour of the yeast suspensions. Estimation of the force needed to separate doublet yeast cells were made using critical shear rate data (i.e., the point at which Bingham flow begins). This estimate was similar to that reported for single antibody bonds and may be due to the presence of lectin-like structures on the yeast cell wall. / Land and Food Systems, Faculty of / Graduate

Thesis (Ph. D.)--Victoria University (Melbourne, Vic.), 2007. / Includes bibliographical references.

Thesis (MSc)--University of Stellenbosch, 2005. / Bibliography. Also available via the Internet.

Thesis (MSc)--University of Stellenbosch, 2006. / Bibliography. Also available via the Internet.

No description available.

Lai-Han Leung. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2003. / Includes bibliographical references (leaves 120-129). / Abstracts in English and Chinese. / Members of Thesis Advisory Committee --- p.i / Acknowledgments --- p.ii / Abstract --- p.iii / Abbreviations --- p.viii / Table of contents --- p.ix / Chapter Ch 1 --- General Introduction / Chapter 1.1 --- Growth hormone --- p.1 / Chapter 1.1.1 --- Physiology of GH --- p.1 / Chapter 1.1.2 --- Biological Functions of growth hormone --- p.2 / Chapter 1.1.3 --- Structure of growth hormone --- p.3 / Chapter 1.1.4 --- The physiological activities of growth hormone --- p.5 / Chapter 1.1.5 --- The importance of increasing grass carp production yield --- p.6 / Chapter 1.1.6 --- Application of recombinant growth hormone --- p.7 / Chapter 1.1.7 --- Application of recombinant grass carp GH --- p.8 / Chapter 1.2 --- Administration of GH to fish --- p.9 / Chapter 1.2.1 --- Methods in the administration of growth hormone to fish --- p.9 / Chapter 1.3 --- Different approaches in the expression of GH --- p.12 / Chapter 1.3.1 --- Bacterial expression system --- p.12 / Chapter 1.3.2 --- Baculovirus and yeast expression system --- p.14 / Chapter 1.4 --- Expression of grass carp growth hormone in yeast (Saccharomyces cerevisiae & Pichia Pastoris) --- p.14 / Chapter 1.4.1 --- Saccharomyces cerevisiae is widely used in the past --- p.14 / Chapter 1.4.2 --- Pichia pastoris is an alternative approach to overcome drawbacks of Saccharomyces cerevisiae --- p.16 / Chapter 1.5 --- Methods for increasing expression level of a cloned gene --- p.20 / Chapter 1.6 --- Purpose of present study --- p.22 / Chapter Ch 2 --- Materials and Method / Chapter 2.1 --- Bacterial strains --- p.23 / Chapter 2.2 --- Yeast strains --- p.23 / Chapter 2.3 --- Plasmids --- p.23 / Chapter 2.4 --- Bacterial culture Media and Solutions --- p.23 / Chapter 2.5 --- Antibiotic Solutions --- p.24 / Chapter 2.6 --- Restriction endonucleases and other enzymes --- p.24 / Chapter 2.7 --- Culture stock solutions --- p.24 / Chapter 2.8 --- SDS-PAGE and Western blot reagents --- p.28 / Chapter 2.9 --- DNA agarose gel --- p.30 / Chapter 2.10 --- General Techniques --- p.32 / Chapter 2.11 --- Construction of recombinant yeast strain --- p.40 / Chapter 2.12 --- Expression of the recombinant protein --- p.42 / Chapter 2.13 --- Purification of the protein --- p.44 / Chapter 2.14 --- Characterization of the protein --- p.46 / Chapter Ch3 --- Results / Chapter 3.1 --- Construction of Recombinant Plasmids --- p.50 / Chapter 3.2 --- Sequencing of the recombinants --- p.61 / Chapter 3.3 --- Linearization and electroporation of recombinant plasmids --- p.69 / Chapter 3.4 --- Optimization of electroporation condition of producing recombinant yeast cells --- p.70 / Chapter 3.5 --- Screening and selection of AOX characteristics (By MM plates) --- p.71 / Chapter 3.6 --- Screening and selection of AOX characteristics (By PCR) --- p.72 / Chapter 3.7 --- Selection of high expression clones --- p.77 / Chapter 3.8 --- Time course expression studies --- p.82 / Chapter 3.9 --- Batch fermentation --- p.89 / Chapter 3.10 --- Purification of r-gcGH --- p.92 / Chapter 3.11 --- Characterization of r-gcGH --- p.100 / Chapter 3.11.1 --- Immunological property of r-gcGH --- p.100 / Chapter 3.11.2 --- Biological activity of r-gcGH --- p.101 / Chapter Ch4 --- Discussion / Chapter 4.1 --- Evaluation of expression profile --- p.108 / Chapter 4.1.1 --- Expression yield --- p.108 / Chapter 4.1.2 --- Efficiency in the cleavage of signal peptide --- p.111 / Chapter 4.2 --- Evaluation of the biological activity of r-gcGH --- p.113 / Chapter 4.3 --- Evaluation of the post-translational modification of r-gcGH --- p.115 / Chapter 4.4 --- Further studies --- p.116 / Reference --- p.120

No description available.

Thesis (Ph. D.)--University of Texas at Austin, 2000. / Vita. Includes bibliographical references (leaves 107-118). Available also in a digital version from Dissertation Abstracts.

Thesis (Ph. D.)--University of Missouri-Columbia, 2002. / Typescript. Vita. Includes bibliographical references (leaves 7191-205). Also available on the Internet.