Thesis (Ph. D.)--University of Missouri-Columbia, 1998. / Typescript. Vita. Includes bibliographical references (leaves 161-182). Also available on the Internet.

Thesis (Ph. D.)--University of Missouri-Columbia, 1998. / Typescript. Vita. Includes bibliographical references (leaves 161-182). Also available on the Internet.

No description available.

Pure cultures o! the yeast S. cerevisiae do not follow the classical continuous culture theory when tested in a variety or chemostats. Using a Coulter Counter, yeast populations were sized and enumerated electronically over a range or dilution rates. Total dry weight and Kjeldahl nitrogen per cell were determined for a variety or dilution rates. From these data it was shown that the yeast definitely increased in size as the dilution rate increased. Also, it appeared that the ratio of rate of synthesis of cell wall material to the synthesis of proteins decreased as the dilution rate increased. Step changes in various environmental factors (dilution rate, medium concentration, glucose concentration, ammonium sulfate, and temperature) indicated that yeast populations may not show a smooth transition from the initial to the final steady states. Decaying oscillations of the yeast population were observed in response to step changes in dilution rate and glucose concentrations. Step changes in ammonium sulfate or in total medium concentrations resulted in smooth responses to a new population level. To investigate the complex responses to dilution rate and glucose a frequency response analysis was employed. The growth of S. cerevisiae varied in a sinusoidal fashion in response to sinusoidal forcing of dilution rate and medium concentration. Bode diagrams were prepared for yeast response to dilution rate and medium concentration. Time constants were determined from the Bode diagrams. The time constants were in the order of several minutes and possible relations to growth control mechanisms can be postulated. The time constants probably pertain to accumulation of intracellular materials. A two-stage continuous culture system was built to investigate the interaction of E. coli and S. cerevisiae. By feeding a continuous pure yeast culture from the first stage into the mixed culture second stage it was found that the E. coli apparently produces a substance that inhibited the growth of yeast. / Doctor of Philosophy

Due to the lead spike and its related health concern in the DC area, Point-of-Use (POU) filters were installed at public schools to reduce lead concentrations in water. However, the installation of POU filter could possibly lead to the growth of bacteria inside the filters, which could lead to health concerns. Therefore, the potential effects of POU filters on microbial growth was investigated. To explore the cause of filter effects on microbial growth, a sampling campaign was carried out between July and December 2017 from 25 outlets within 5 elementary schools in the DC area. The applicability of flow cytometry results as a quantification method was validated and then used to quantify the biological growth. Our results revealed that the installation of POU filters may lead to nitrification and an increase in microbial growth. Along with the increase in microbial growth, the microorganism community "fingerprints" based on flow cytometry data showed that the installation of filter could also shift the community distribution of bacteria based on their morphology. This study serves as a preliminary study to investigate the mechanics of microbial colonization on POU filters. / Master of Science / Due to the lead spike and its related health concern in the DC area, Point-of-Use (POU) filters were installed at public schools to reduce lead concentrations in water. POU filters are usually installed at sinks and fountains and the Water Quality Association reported that 41% of American homes used POU filters by 2000. However, the installation of POU filter could possibly lead to the growth of bacteria inside the filters, which could lead to health concerns. Therefore, the potential effects of POU filters on microbial growth was investigated. To explore the cause of filter effects on microbial growth, a sampling campaign was carried out between July and December 2017 from 25 outlets within 5 elementary schools in the DC area. Flow cytometry is an optical technology that can measure and then analyze multiple physical characteristics of a single particle as it flows in a fluid stream. The applicability of flow cytometry results as a quantification method was validated and then used to quantify the biological growth. Our results revealed that the installation of POU filters may lead to nitrification and an increase in microbial growth. Along with the increase in microbial growth, the microorganism community “fingerprints” based on flow cytometry data showed that the installation of filter could also shift the community distribution of bacteria based on their morphology. This study serves as a preliminary study to investigate the mechanics of microbial colonization on POU filters.

<p>The most common disease causing elements in feed is of microbial nature. Therefore it is of great importance for horse owners to be familiar with the fundamental requirements for microbial growth in feeds and the problems that can originate in case of insufficient handling. However, horse owners are not organized in a way that makes it easy to reach them with information as a target group. Additionally, most horse owners only have one horse and limited possibilities for education in feed safety. Thus, there is need for an easy accessed education material that is explicitly directed towards horse owners. The fundamental content of such an education material was composed in this project. Focus was on the importance of good microbial quality in horse feed and the material was structured into three chapters; FEED SAFETY, MICROORGANISMS IN FEEDS and CONSERVATION, STORING AND FEEDING. The aim was to publish the material as part of a larger web based education package on the web page, http://www.sva.se of the Swedish National Veterinary Institute. The basic structure for such a web education was also composed in this project.</p>

No description available.

The most common disease causing elements in feed is of microbial nature. Therefore it is of great importance for horse owners to be familiar with the fundamental requirements for microbial growth in feeds and the problems that can originate in case of insufficient handling. However, horse owners are not organized in a way that makes it easy to reach them with information as a target group. Additionally, most horse owners only have one horse and limited possibilities for education in feed safety. Thus, there is need for an easy accessed education material that is explicitly directed towards horse owners. The fundamental content of such an education material was composed in this project. Focus was on the importance of good microbial quality in horse feed and the material was structured into three chapters; FEED SAFETY, MICROORGANISMS IN FEEDS and CONSERVATION, STORING AND FEEDING. The aim was to publish the material as part of a larger web based education package on the web page, http://www.sva.se of the Swedish National Veterinary Institute. The basic structure for such a web education was also composed in this project.

The purpose of this study was to assess the growth of spoilage and pathogenic bacteria on low sodium concentration sliced cooked bologna under refrigerated storage conditions. In study 1, the effect of three different sodium concentrations (1%, 2% and 3%) and two packaging conditions (aerobic and vacuum) on growth of a cocktail of inoculated spoilage bacteria such Lactobacillus curvatus, Leuconostoc mesenteroides, Brochothrix thermosphacta and Pseudomonas fluorescens were investigated by using culture-dependent and culture-independent techniques. In general, reducing the sodium concentration from 2% (the current industry standard) to 1% NaCl in the cooked bologna system did not have a significant effect on microbial growth. The utilization of Ion Torrent high-throughput sequencing in this study allowed the description of the total microbial community present on sliced cooked bologna. Taxonomic analysis revealed the microbial community belongs to the phyla Firmicutes, Proteobacteria, Actinobacteria and Bacteroidetes. Finally, in this study, in situ meat redox measurement values were collected over time using platinum electrodes placed on top of, and in between bologna slices. While the redox values obtained were, in general, consistent with increasing bacterial cell numbers, issues of reproducibility and consistency were evident. The second study focused on the impact that the addition of a bacteriocin, Micocin X®, to the meat blend would have on growth of spoilage bacteria and in particular, Listeria monocytogenes, in vacuum-packaged cooked bologna formulated with 1% and 3% NaCl. In general, results demonstrated Micocin X® had a significant effect on the growth of Pseudomonas fluorescens and Listeria monocytogenes; however, no substantial effect was assessed in the control of lactic acid bacteria or Brochothrix thermosphacta.

Thesis (Ph. D.)--Rutgers University, 2009. / "Graduate Program in Oceanography." Includes bibliographical references.