Reproduction de : Thèse de doctorat : Génie des procédés et de l'environnement : Toulouse, INPT : 2007. / Titre provenant de l'écran-titre. Bibliogr. 179 réf.

Reproduction de : Thèse de doctorat : Génie des procédés et de l'environnement : Toulouse, INPT : 2008. Reproduction de : Thèse de doctorat : Chimie : Beyrouth, Université Saint-Joseph : 2008. / Thèse soutenue en co-tutelle. Titre provenant de l'écran-titre. Bibliogr. 205 réf.

Due to the depletion of petroleum reserves and environmental concerns, bioethanol has been identified as an alternative fuel to petrol. Bioethanol is a fuel of bio-origin derived from renewable biomass. Starch and sugar containing materials are the primary sources of carbon for bioethanol production. Starch is firstly hydrolysed into simple sugars which are later fermented to bioethanol using Saccharomyces cerevisiae (S. cerevisiae). The fermentation of sugars to bioethanol is however limited by inhibition of S. cerevisiae by the major product of the process, bioethanol. The challenge is thus in keeping the bioethanol concentration at levels which are not harmful to the fermenting organism. Keeping bioethanol concentration low in the broth will provide a suitable environment for yeast to grow and thus increase the overall production. Currently bioethanol producers use high water dilution rates to keep the bioethanol concentrations in the broth low enough so that yeast is not harmed. This excess water has to be removed in the downstream process, which is expensive. The use of excessive amounts of water in the fermentation can be avoided by continual removal of bioethanol from the broth. During this investigation the experimental conditions for the hydrolysis process were determined. A pH of 5.5 was determined as the best pH for Termamyl SC at 95°C with a pH of 5.0 for Spirizyme Fuel at 55°C during the liquefaction and the saccharification step, respectively. During the fermentation process the influence of yeast concentration on bioethanol production was investigated by varying the yeast concentration between 2 g.L-1 and 7 g.L-1. A yeast concentration of 5 g.L-1 produced the highest bioethanol yield of 0.48 g.g-1 after 48 hours of fermentation using S. cerevisiae. Later during the investigation a coupled fermentation/pervaporation system was employed in a batch system for continual removal of bioethanol in the fermentation broth in a process called simultaneous fermentation and separation (SFS). Through the continuous removal of bioethanol from the fermentation broth, the bioethanol concentration in the broth was kept low enough so that it was not harmful to the fermenting organism but the overall fermentation yield was not improved. Pervaporation is a membrane separation process used to separate azeotropic mixtures such as bioethanol and water. It is highly efficient, cost effective and uses less energy than distillation. During the SFS process a bioethanol yield of 0.22 g.g-1 was obtained. The SFS process yield for bioethanol was low compared to 0.45 g.g-1 of the traditional batch fermentation process. The lower overall bioethanol yield obtained in the SFS process could be attributed to only the supernatant being used in the SFS process and not the entire fermentation broth as in the traditional process. The results from this study proved that the SFS process was less efficient compared to the traditional batch fermentation process with respect to the bioethanol yield, but that the fermentation could be carried out without the necessity for additional process water. / Thesis (M.Sc. Engineering Sciences (Chemical and Minerals Engineering))--North-West University, Potchefstroom Campus, 2010.

Due to the depletion of petroleum reserves and environmental concerns, bioethanol has been identified as an alternative fuel to petrol. Bioethanol is a fuel of bio-origin derived from renewable biomass. Starch and sugar containing materials are the primary sources of carbon for bioethanol production. Starch is firstly hydrolysed into simple sugars which are later fermented to bioethanol using Saccharomyces cerevisiae (S. cerevisiae). The fermentation of sugars to bioethanol is however limited by inhibition of S. cerevisiae by the major product of the process, bioethanol. The challenge is thus in keeping the bioethanol concentration at levels which are not harmful to the fermenting organism. Keeping bioethanol concentration low in the broth will provide a suitable environment for yeast to grow and thus increase the overall production. Currently bioethanol producers use high water dilution rates to keep the bioethanol concentrations in the broth low enough so that yeast is not harmed. This excess water has to be removed in the downstream process, which is expensive. The use of excessive amounts of water in the fermentation can be avoided by continual removal of bioethanol from the broth. During this investigation the experimental conditions for the hydrolysis process were determined. A pH of 5.5 was determined as the best pH for Termamyl SC at 95°C with a pH of 5.0 for Spirizyme Fuel at 55°C during the liquefaction and the saccharification step, respectively. During the fermentation process the influence of yeast concentration on bioethanol production was investigated by varying the yeast concentration between 2 g.L-1 and 7 g.L-1. A yeast concentration of 5 g.L-1 produced the highest bioethanol yield of 0.48 g.g-1 after 48 hours of fermentation using S. cerevisiae. Later during the investigation a coupled fermentation/pervaporation system was employed in a batch system for continual removal of bioethanol in the fermentation broth in a process called simultaneous fermentation and separation (SFS). Through the continuous removal of bioethanol from the fermentation broth, the bioethanol concentration in the broth was kept low enough so that it was not harmful to the fermenting organism but the overall fermentation yield was not improved. Pervaporation is a membrane separation process used to separate azeotropic mixtures such as bioethanol and water. It is highly efficient, cost effective and uses less energy than distillation. During the SFS process a bioethanol yield of 0.22 g.g-1 was obtained. The SFS process yield for bioethanol was low compared to 0.45 g.g-1 of the traditional batch fermentation process. The lower overall bioethanol yield obtained in the SFS process could be attributed to only the supernatant being used in the SFS process and not the entire fermentation broth as in the traditional process. The results from this study proved that the SFS process was less efficient compared to the traditional batch fermentation process with respect to the bioethanol yield, but that the fermentation could be carried out without the necessity for additional process water. / Thesis (M.Sc. Engineering Sciences (Chemical and Minerals Engineering))--North-West University, Potchefstroom Campus, 2010.

Th.--Sci. phys.--Nancy--I.N.P.L., 1985.

Typescript (photocopy). / Digitized by Kansas Correctional Industries

Pediococcus cerevisiae, Lactobacillus casei, Lactobacillus plantarum, Leuconostoc mesenteroides, Lactococcus diacetylactis Bifidobacterium bifidum, Leuconostoc oenos, and mixed cultures of Propionibacterium shermanii and P. cerevisiae were used to ferment cucumber juice brine (CJB) at 22-26°C for 1.5 months. Sugar utilization ranged from 14.6 to 86.1%. pH of the fermented CJB ranged from 3.24 to 4.12 and titratable acidity ranged from 0.30 to 0.93%. All strains tested degraded malic acid and citric acid. Leu. mesenteroides and Leu. oenos did not utilize citric acid for diacetyl-acetoin production. The concentration of acetic, propionic and lactic acids varied among the fermentation treatments. The heterofermenters produced high concentrations of CO₂, ethanol and mannitol and CJB with high volatile/nonvolatile acid ratios. The fermentation balance indicated that sugars had been used to produce compounds not measured in this study. Twelve aroma and six flavor by mouth descriptors were used to describe flavor of the final products in the trained panel descriptive analysis. Sourness intensity was the only sensory descriptor that correlated with the chemical analysis data. The intensities of seven aroma and three flavor by mouth descriptors were significantly different (p < 0.05) among treatments. Aroma preference mean scores from 9-point hedonic scale ranged from 4.69-5.39; they were not significantly different (p > 0.05). Formation and Potential Industrial Applications of An Insoluble Polyelectrolyte Complex: Chitosan-Polyacrylic Acid Chitosan and polyacrylic acid mixtures were prepared in different mole ratios and at different ionic strengths (0.025-0.300). No insoluble complex formation at pH=2 was detected. In the 3 to 6 pH range, the maximum complex formation occurred at different mole ratios. The complex composition is affected by pH but not by ionic strength. An electrostatic interaction between -COO⁻ and -NH₃+ groups was involved in complex formation. This study suggests that process recommendations for industrial application of chitosan as a coagulating agent can be made based on the ionic strength, pH and charge group concentration of the fluid to be treated. / Graduation date: 1990

It has been reported recently that extracts of filbert nuts demonstrate considerable proteolytic activity on a non-fat milk solids substrate. The addition of these extracts to cheddar cheese, in an attempt to enhance the rate of ripening, has been suggested. In these experiments, the extracts of two varieties of filbert nuts, i.e. Du Chilly and Barcelona, were added to cheddar cheese samples at the milling stage of manufacture. The rate of proteolysis, in the cheese samples, was determined quantitatively by the increase in soluble protein content over a three month period. At the termination of these experiments a taste evaluation was performed on all cheese samples. A statistical analysis on the results of the soluble protein analyses showed that the proteolysis in the treated cheese samples was significantly greater than the proteolytic breakdown in the control samples. A defatted extract of Barcelona variety of filbert nuts was the most effective treatment of enhancing the proteolysis in the cheese samples. The results of the taste tests showed that no significant improvement in the flavor of the cheese resulted from the addition of filbert extracts. / Graduation date: 1951

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