The aim of this diploma thesis was the selection of appropriate indigenous yeasts for wine production. Tested yeasts were isolated from the grapes from the winery Maňák Žádovice. The yeasts isolated within theses in 2009 – 2012 have been also tested, and commercial wine yeast have been tested for comparison. In the theoretical part the focus is on the technology of wine, in particular fermentation. The work is also focused on yeasts metabolism and taxonomy. There was described the principle of PCR-RFLP, and methods used to characterize the properties of isolated yeasts. In the experimental part was made isolation of yeasts, theirs identification using PCR-RFLP and to select the most suitable yeast in wine making proces were performed physiological tests.

No abstract available / Thesis (PhD)--University of Pretoria, 1953. / Original thesis in typescript / Includes bibliographical references. / Production Animal Studies / PhD / Unrestricted

Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Nutrition and Food Science, 1979. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND SCIENCE. / Vita. / Bibliography: leaves 296-304. / Ph.D.

The potential of enhancing lipid accumulation in municipal sewage activated sludge via fermentation of lignocellulose biomass hydrolyzate was investigated. The overall objective was to increase the levels of feedstock lipids in the activated sludge biomass and increase its biodiesel yield via in situ or ex situ transesterification; and improve its cost competitiveness as an abundant feedstock source for biofuels production. To reduce production costs and maintain environmental sustainability, influent wastewater and waste lignocellulose biomass hydrolyzate were used as cultivation media and substrate, respectively. However, lignocellulose hydrolyzates also contain degradation by-products such as furfural and acetic acid that are known to exert inhibitory effects on microorganisms; hence their effects on the fermentative performance of activated sludge were investigated and fermentation strategies were proposed and evaluated to counteract the microbial toxicity of these compounds. The utilization rate and efficiency of xylose by activated sludge microorganisms for lipid production was also evaluated as pentose sugars such as xylose usually constitute a major percentage of lignocellulose hydrolyzates. Furthermore, variations in the population profile of activated sludge microbiota were determined via 16S rRNA sequence analysis to determine the effect of sugar fermentation at different initial conditions. Results show that activated sludge lipid contents and biodiesel yield could be enhanced by fermentation of sugars at a high initial C:N ratio (70:1). Furfural was found to be highly inhibitory to microbial growth and lipid accumulation while high initial acetic acid concentrations enhanced biomass production but not lipid formation. Xylose was also utilized more efficiently than glucose by the activated sludge microorganisms for biomass and lipid production albeit at relatively slower rates; hence sugar mixtures derived from lignocellulose could be utilized for the process. Semicontinuous and continuous fermentation modes were proposed and evaluated as strategies to reduce inhibitory effect of furfural and acetic acid and improve lipid productivity, but the lack of nutrient supplementation prevented the cultures from sustaining microbial growth and lipid production, leading to cell death and washout. Finally, the reduction in the diversity of the activated sludge microbiota could point to specific microbial strains that are mainly responsible for lipid accumulation.

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In recent years economic, environmental, and strategic concerns over the use of petroleum resources have led to increased interest in renewable resources. Biomass gasification produces a synthesis gas composed of primarily carbon monoxide, hydrogen, and carbon dioxide, which can be fermented into a variety of fuels and chemicals. This study evaluated the performance of a two-stage approach to batch synthesis gas fermentations. The first stage employs a rich medium optimized for cell growth, while the second stage is designed to maximize production of acetic acid from synthesis gas. This two-stage approach is hypothesized to be more metabolically efficient than previous single-stage designs. This study presents the evaluation of known acetic acid producing organisms described in the literature, and efforts to isolate a novel microbial catalyst for synthesis gas fermentations. Finally, new techniques were developed and implemented in order to develop a more effective system for batch synthesis gas fermentations.

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