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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.

Impact of stress on Saccharomyces cerevisiae during scotch grain whisky fermentation

Cheung, Anne Wai Yin January 2014 (has links)
High gravity fermentation has been employed to improve the efficiency and sustainability of the Scotch grain whisky fermentation process. However, the use of high gravity wort creates stressful conditions for the yeast; thus it is important to understand the stress tolerances and responses of distilling yeast. In this thesis, the impact of stress on ethanol tolerance was initially assessed using a number of distilling Saccharomyces cerevisiae strains; one of which, S. cerevisiae D 1 showed the highest ethanol tolerance. Furthermore, variation in ethanol tolerance and genetic integrity was observed between isolates of S. cerevisiae D 1 supplied as creamed and dried yeasts. S. cerevisiae D 1 was then monitored during laboratory and industrial scale grain whisky fermentations, focusing on its stress response under fermentation conditions. There are several interesting findings; first S. cerevisiae D1 utilised proline, which may be a part of the stress response. Second, the results also showed the general stress response was activated in the early stages of fermentation and was being taken over by individual stress responses as fermentation proceeded. The results suggest the yeast may also have been stressed as a consequence of the propagation process. Furthermore, expression of ethanol stress response genes were responded to changes in intracellular ethanol concentration. These results provide insight into the stress response of yeast under fermentation conditions and will provide valuable information for developing future yeast strains suitable for high gravity fermentation. Finally, the identification of presumptive lactic acid bacteria isolated from the fermentation was also studied. The result highlighted the diversity of the microflora presented and, as lactic acid bacteria is desirable for their contribution to flavour, better understanding of the microflora could lead to an improved flavour profile.

Optimisation of microbial function for the manufacture of bio-fuels from agricultural, domestic and industrial waste materials

Bell, Andrew Norman William January 2014 (has links)
In industrial fermentation processes, alcohols accumulate and become a limiting factor to their own production through metabolic rate limitation leading to reduction of overall yield. Fermentation efficiency is reduced directly by the action of alcohols through disruption of cellular macromolecular structures. This reduces a cell's ability to undergo life processes, leading inexorably to cell death. In order to offset this ethanol-induced stress, cells produce a diverse range of stress protectants (compatible solutes). These have proven to reduce macromolecular disruption, even from agents with chaotropic modes of action and, thus, aid overall cellular stabilisation. A library of yeast species and strains was constructed to allow the identification of uniquely tolerant or intolerant stress resistance patterns, in the presence of diverse stressors. After selecting yeasts that ' proved most capable of survival across a range of stress conditions, their intracellular polyols were identified and quantified. Beta-Galactosidase, was used as a single component enzyme model system. This allowed analysis of the effects that aliphatic alcohols, compatible solutes and a combination thereof, had on the kinetic parameters of the enzyme. Whole cell stress effects were similarly examined to determine the impact of compatible solute supplementation at biologically relevant concentrations on cell growth and fermentation ability. Polyols were found to partially restore enzyme kinetic parameters and cellular growth rate during alcohol-induced inhibition. At moderate, intracellularly relevant concentrations they compounded the problem. Ultimately there were indications that some compatible solutes may be useful at low concentrations during later stages of fermentation. This thesis provides some of the basic information to enable further work in establishing appropriate supplementation procedures and the economic benefits (if any) thereof.

The development of encapsulated probiotic bacteria with prebiotics incorporated into cereal beverages

Pispan, Supaporn January 2011 (has links)
Most probiotic products are dairy-based and require refrigeration, but there are currently no spray dried probiotic powders sold commercially today. The aim of this research is to develop instant cereal beverage using an oat-based formulation containing the probiotic organism Lactobacillus acidophilus. Escherichia coli K12 was initially used as a reference Gram negative microorganism to compare with the Gram positive L. acidophilus. The work started with the examination of growth to determine the timings required to harvest cells in the mid-log phase and the early-stationary phase of both bacteria. Spray only experiments were then performed which showed that atomisation itself did not cause any significant effect on cell survival of either cultures, either in the mid-log or early-stationary phases. The spray drying experiments found that cells harvested in the early-stationary phase had a greater heat resistance than those cultured in their mid-log phase at the same outlet temperature. It was also found that the higher the drying outlet temperature, the lower was the cell survival rate. The best survival rates were found when spray drying at drying outlet temperatures lower than 80°C. E coli K12 was found to have a lower level of survival than L. acidophilus especially when spray dried with maltodextrin without culture broth components present. This can be attributed to the much thinner cell wall of the Gram negative E coli K12 bacterium. The optimal growth phase (early stationary) and spray drying outlet temperature (80°C) were then taken forward in to the next study for L. acidophilus when various combinations and ratios of proteins (either whey protein, isolated soy protein or skim milk) and sugars (either maltose, lactose or fructose), and maltodextrin were tested. Cell survival rates after spray drying were tested after rehydrating in phosphate buffer solution (PBS), simulated gastric juice (SGI) or 2% Bile solution for 1 hour, although significantly better survival was observed if left to rehydrate for 12 hours. By directly examining experimental data and also using Response Surface Methodology (RSM) it was found that in general increasing the protein level gave a higher cell survival rate after rehydrating in PBS, SGI and bile solution, while formulations containing no protein showed the lowest survival rate. It was strongly shown that the presence of protein above 50%, particularly milk protein, does protect cells in these harsher environments. The sugar contents were limited to a maximum value of 25% due to stickiness limitations. It was found that maltose produced better results than lactose or fructose. Incorporation of a liquid oat drink into the formulation to replace distilled water only produced a slight lowering of survival levels if protein levels were still maintained, but replacing the protein mixture by a prebiotic (Orafti®P95) produced adverse results. After storage for 3 months these spray dried cultures showed high stability when stored at refrigerator temperatures (4°C) although acceptable levels of survival were also found when stored at room temperature. A simulated hydration/digestion was performed by which cells were hydrated in distilled water and exposed to SGI and bile solution in turn. These showed very good results and indicated that the bacteria could be transported to the gut in a viable state. The recommended formulation for spray dried L. acidophilus encapsulated with whey protein, maltose and maltodextrin incorporated into prebiotics and oat drink is 16%, 2%, 2%, 0% and 80% respectively.

Thermochemical conversion of Brewers Spent Grain combined with catalytic reforming of pyrolysis vapours

Mahmood, Asad January 2015 (has links)
The brewing process is an energy intensive process that uses large quantities of heat and electricity. To produce this energy requires a high, mainly fossil fuel consumption and the cost of this is increasing each year due to rising fuel costs. One of the main by-products from the brewing process is Brewers Spent Grain (BSG), an organic residue with very high moisture content. It is widely available each year and is often given away as cattle feed or disposed of to landfill as waste. Currently these methods of disposal are also costly to the brewing process. The focus of this work was to investigate the energy potential of BSG via pyrolysis, gasification and catalytic steam reforming, in order to produce a tar-free useable fuel gas that can be combusted in a CHP plant to develop heat and electricity. The heat and electricity can either be used on site or exported. The first stage of this work was the drying and pre-treatment of BSG followed by characterisation to determine its basic composition and structure so it can be evaluated for its usefulness as a fuel. A thorough analysis of the characterisation results helps to better understand the thermal behaviour of BSG feedstock so it can be evaluated as a fuel when subjected to thermal conversion processes either by pyrolysis or gasification. The second stage was thermochemical conversion of the feedstock. Gasification of BSG was explored in a fixed bed downdraft gasifier unit. The study investigated whether BSG can be successfully converted by fixed bed downdraft gasification operation and whether it can produce a product gas that can potentially run an engine for heat and power. In addition the pyrolysis of BSG was explored using a novel “Pyroformer” intermediate pyrolysis reactor to investigate the behaviour of BSG under these processing conditions. The physicochemical properties and compositions of the pyrolysis fractions obtained (bio-oil, char and permanent gases) were investigated for their applicability in a combined heat power (CHP) application.

Placebo expectancy effect of consuming psychoactive beverages on cognition and mood

Johal, Jaspreet January 2015 (has links)
Energy drinks have become very popular over the past few years with over half the student population in colleges and universities consuming them at least once a month (Malinauskas et al., 2007). It has been reported that the most common reasons why students consume energy drinks are to maintain alertness, reduce symptoms of hangover, increase energy, to help with driving and to prevent sleepiness (Attila and Cakir, 2011; Malinauskas et al., 2007). Previous research has suggested that energy drinks enhance sensorimotor speed, behaviour, and reduce levels of fatigue (Alford et al., 2001; Horne and Reyner, 2001; Howard and Marczinski, 2010; Kennedy and Scholey, 2004; Smit et al., 2004). The two key ingredients found in energy drinks are caffeine and glucose which have been examined together and alone, which have indicated enhanced reaction times, improvement in both verbal memory and sustained attention and more recently there is evidence to show that expectancy may play a key role in predicting intentions of future consumption (Adan and serra-Grabulosa, 2010). According to Kirsch (1997) people have specific expectations when they consume psychoactive substances that trigger physiological and psychological reactions, which tend to be independent of the psychoactive substance ingested. The concept of expectancy effects can be unambiguous especially when the information provided to the participants prior to the experimental study is specific to a possible outcome response. This thesis investigated the extent of expectancy effect on cognition and mood when psychoactive drinks containing caffeine and glucose were consumed in comparison to non-psychoactive drinks. The investigation commenced with examining the independent effects of caffeine and glucose, followed by the combination of caffeine and glucose as an energy drink on mood and cognition. The investigation advanced by comparing drink presentation effects (i.e., consuming the experimental drink from a branded bottle versus from a glass) irrespective of drink content on mood and cognition. Finally, the investigation lead to exploring what factors may predict expectancy effects when participants’ consumed psychoactive drinks among healthy adults. This was done by applying the Theory of Planned Behaviour model (TPB) (Azjen, 1991) to explore the contribution of specific attitudes, subjective norms and perceived behavioural control to the extent of expectancy effects as well as to behavioural intention, with additional variables including; beliefs, habits, past-behaviour, selfidentity. Self-identity representing someone who drinks energy drinks regularly. The level of internal consistency for Cronbach’s alpha was conducted for each variable within the TPB model and for the additional variables included for test reliability. This thesis consisted of four studies, which found that consumption of caffeine and glucose independently and also in combination resulted in psychoactive effects on mood and cognition. Experiment 2 was the only study, which indicated an expectancy effect for immediate verbal recall task and the mood subscale tension. Conversely, for experiment 4 there was a reverse effect found for the immediate verbal recall task. However, there were significant expectancy and psychoactive effects found for mood subscales throughout the four studies. It was also found that the TPB model had two significant variables past-behaviour and self-identity predicted intentions suggesting that participants who regularly consume psychoactive beverages have salient beliefs about consuming psychoactive drinks and the TPB model can be utilised to predict their intentions. Furthermore, the Theory of planned behaviour model found that habit and self-identity significantly predicted participants’ expectancy effects on the vigour. Indicating consumers of energy drinks are familiar with expected outcome response. This model was unsuccessful in predicting expectancy response for cognitive performance. Thus, overall the findings from the four studies indicated that caffeine and glucose have cognitive enhancing properties, which also positively improve mood. However, expectancy effects have been identified for mood only, whereas the overall findings within this thesis were unable to identify significant predictors of expectancy effect and response.

Kinetics of alcholic fermentation in a tower fermenter

Burgess, Kenneth John January 1979 (has links)
No description available.

Binding properties of the cell wall of Saccharomyces cerevisiae

Jayatissa, Perera M. January 1976 (has links)
A study was made of binding of an antifoam preparation containing polydimethylsiloxane (PDS) to cells of Saccharomyces cerevisiae NCYC 366. These cells bound approximately 2.1 mug PDS per 2 x 107 organisms when suspended in 0.1 M KH2PO4 buffer (pH 4.5) containing Antifoam M-10 (to give 19 mug PDS per ml). A decrease in the concentration of any one of the two emulsifiers, polyoxyethylene sorbitan monostearate or glycerol monostearate caused an increase in the saturation concentration of PDS bound by the organisms, while a decrease in the concentration of the thickener, sodium carboxymethyl cellulose caused a decrease. The sites involved in binding PDS were indicated to be located in the cell-wall phosphomannan-protein of the organisms by studies made on PDS binding by whole cells, PDS release by saturated organisms, analyses of isolated walls and surface properties of organisms, before and after chemical and enzymic treatments. The surface charge of the organisms at different pH values had no effect on PDS binding. Binding of PDS had a masking effect on the electrophoretic mobility, binding of antibody and binding of concanavalin A by the organisms, but had no effect on the release of invertase. An examination was made of the ability of each of 4 strains of Saccharomyces cerevisiae to flocculate following the excision of the phosphodiester linkages of cell-wall phosphomannan. Treatment of isolated walls of each of the 4 strains with hydrofluoric acid (58 - 62%, v/v) removed most of the phosphorus without extensive losses of other components. Treatment of whole cells with the same reagent increased the sedimentation rates of both flocculent and non-flocculent cells. The presence of Ca2+ ions was found to be essential for the expression of flocculence either inherent or induced by hydrofluoric acid treatment. Esterification of surface carboxyl groups decreased the sedimentation rates of both untreated flocculent cells and hydrofluoric acid-treated organisms. Inclusion of mannose in the suspending medium deflocculated untreated flocculent cells but failed to deflocculate hydrofluoric acid-treated organisms. The phosphorus contents of the outer layers of the cell-wall as indicated by the electrophoretic mobility at pH 4.0 or the amount of calcium bound by isolated walls was not related to the flocculation characteristics of the organisms.

Mixing, mass transfer and bioreaction in an industrial fermenter

Vlaev, Dimiter S. January 1999 (has links)
No description available.

The characterisation and delivery of flavonoids and other minor components in traditional food ingredients

Donnelly, Catherine M. January 2016 (has links)
The primary aim of this research was to determine whether herbal infusions, yerba mate (Ilex paraguariensis A. St.-Hilaire) and rooibos (Aspalathus linearis (Burm. F.) R. Dahlgren), could make a significant contribution to the dietary intake of polyphenols. A secondary aim was to determine whether the trace elemental content of these herbal infusions were of dietary significance. The total polyphenol (using the Folin-Ciocalteu assay), the individual polyphenol compounds (by ultra-high performance liquid chromatography) and the trace element content (by inductively coupled plasma mass spectrometry) was determined in the leaf and infusions of 47 yerba mate and 54 rooibos commercial products (tea bags and loose leaf). This research, for the first time, developed an extraction procedure and two ultra-high performance liquid chromatography methods that enabled the determination of 38 polyphenol compounds in yerba mate and 22 in rooibos samples. Fourteen trace elements were determined in leaf and infusion samples, enabling the extraction efficiency of trace elements to be calculated for the first time for these herbs. The total polyphenol content of green yerba mate (79.9 – 303.1 mg gallic acid equivalents (GAE)/ 200 ml) and fermented rooibos infusions (40.1 – 101.9 mg GAE/ 235 ml) was within the range of that of other beverages (tea, coffee, fruit juices) as reported in the literature. It was noted that yerba mate in tea bags contained significantly higher levels of polyphenols than loose leaf products (ANOVA and Tukey’s test, probability, p < 0.05) due to the absence of stems. The total chlorogenic acid content of green tea bag yerba mate (90.1 – 395.4 mg/200 ml) and the total flavonoid content of fermented rooibos infusions (6.65 – 20.03 mg/235 ml) was higher than that reported for coffee and fruit juices, respectively. It was concluded that regular consumption of 1 -2 cups/day of yerba mate or rooibos would make a significant contribution to the dietary intake of polyphenols. The manganese content of a yerba mate infusion (360 – 2985 µg/200 ml) would provide 39.7 – 60.8% for men and 57.1 – 86.2% for women of the World Health Organisation (WHO) adequate daily intake of manganese. Therefore, 1 – 2 cups per day could provide the entire daily nutritional requirement of manganese. In addition, consumption of yerba mate in the traditional South American manner could provide nutritionally significant levels of chromium, copper and zinc. The trace element content of rooibos was not nutritionally significant.

Influence of sodium chloride on wine yeast physiology and fermentation performance

Logothetis, Stelios January 2009 (has links)
This thesis concerns research into the influence of salt on physiology of the yeast, <i>Saccharomyces cerevisiae</i>. Specifically, the work focused on how sodium chloride affected the growth, viability and fermentation performance in industrial (winemaking) strains of this yeast in both laboratory-scale and industrial-scale experiments. Comparative fermentations were also conducted with selected non-<i>Saccharomyces</i> yeasts that are of relevance in enology. One of the main findings of the research presented involved the influence of salt "preconditioning” of yeasts which represents a method of pre-culturing cells in the presence of salt in an attempt to improve subsequent fermentation performance. Such an approach resulted in preconditioned yeasts having an improved capability to ferment high-sugar containing media with increased cell viability and with elevated levels of produced ethanol. Salt-preconditioning was most likely influencing the stress-tolerance of yeasts by inducing the synthesis of key metabolites such as trehalose and glycerol which act to improve cells’ ability to withstand osmostress and ethanol toxicity. The industrial-scale trials using salt-preconditioned yeasts verified the benefit of the physiological engineering approach to practical winemaking fermentations. Benefits were also observed in a specialized fermentation system (WITY produced by the first letters of the words Wine, Immobilization, Tower, and Yeast) that utilized immobilized yeast. Overall, this research has demonstrated that a relatively simple method designed to physiologically adapt yeast cells - by salt-preconditioning - can have distinct advantages for alcohol fermentation processes.

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