Thesis (Ph. D. engineering science)--Washington State University, December 2007. / Includes bibliographical references.

Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1992. / Vita. Abstract. Includes bibliographical references (leaves 196-198). Also available via the Internet.

Adaption to environmental stresses is vital for the survival of all organisms living in any environment. Two of the major environmental factors in the deep sea environment are high hydrostatic pressure and high salt concentration. Hydrostatic pressure and osmotic pressure share similarities in their effects on organisms living in the deep sea but this overlap has been little explored. Major studies from Japan and California over the last 40 years have shown the effects of hydrostatic pressure on bacteria from the deep sea (see [1] for a review). These are complemented by work by Yancey et al. [2] showing that specific solutes accumulated in response to osmotic pressure in fish have the ability to enhance resistance to hydrostatic pressure. However, this work has been done in vitro or with larger organisms and not much is known about the overlap of osmotic and hydrostatic pressure in bacteria. In this study I investigated the effects of osmotic and hydrostatic pressure on two model organisms: Photobacterium profundum and Escherichia coli. In order to accomplish this task I developed novel imaging equipment which allows for high resolution imaging of bacteria at pressure. I also developed a new method of growing bacteria in 96-well plates at high pressure, which lead to the identification of a hierarchy of genes essential for the growth of E. coli at pressure. I used the same 96-well plate technique to monitor the growth of P. profundum at differing osmotic and hydrostatic pressures. Furthermore I also attempted to analyse the solutes accumulated by different strains of P. profundum in response to osmotic and hydrostatic pressures.

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Filtered bright and unfiltered hazy lager beer samples were either treated with high hydrostatic pressure (200, 250, 300, 350 MPa for 3, 5 and 10 min at 10&deg / C and 20&deg / C) or conventional heat pasteurization (60&deg / C for 15 min). Treatments did not affect ethanol, extract, fermentation degree, density and pH in comparison with untreated beers. Both treatments produced microbiologically stable products. Bitterness, color, protein sensitivity and chill haze parameters were affected by both the HHP and heat treatment. A storage period of 56 days showed that HHP and heat pasteurization had similar results in terms of pH and color. However, HHP treated samples had lower bitterness and protein sensitivity and higher chill haze values than the heat pasteurized samples which indicates HHP treatment had a positive effect on bitterness and protein sensitivity at the end of the storage period. The microbiological stability of HHP treated beers was comparable with heat-treated beers, and the development of both lactic and acetic acid bacteria was inhibited for 56 days of storage. Unfiltered beer samples had 7. 48, 7.15 and 2.64 log10cfu/ml of total yeasts, total aerobic and lactic acid bacteria counts, respectively. No colony formation of lactic acid bacteria was observed when the samples were pressurized at pressures equal to or higher than 300 MPa at 10&deg / C and 20&deg / C for 5 and 10 min. Total aerobic and total yeasts counts demonstrated more than 6 and 7 log-cycle reduction when pressurized at 350 MPa at 10&deg / C and 20&deg / C for 10 min, respectively. Heat treatment gave similar results in terms of log reductions as HHP.

Thesis (Ph. D.)--Ohio University, 2001. / Title from PDF t.p.

Thesis (M.S.)--Ohio University, June, 2000. / Title from PDF t.p.

Thesis (M.S.)--Oregon State University, 2008. / Printout. Includes bibliographical references (leaves 37-40). Also available on the World Wide Web.

Thesis (M.S.)--Ohio University, June, 2004. / Includes bibliographical references (p. 105-107).

Thesis (M.S.)--Rutgers University, 2008. / "Graduate Program in Food Science." Includes bibliographical references (p. 101-106).