Browsing by Subject "Fermentation"
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Item Bio-fuel production by using integrated anaerobic fermentation.(2012-01) Xu, LeiSaccharification is one of the most critical steps in producing lignocellulose-based bio-ethanol through consolidated bioprocessing (CBP). However, extreme pH and high ethanol concentrations are commonly considered potential inhibitors for the application of Clostridium sp. in CBP. The fermentation of several saccharides derived from lignocellulosics was investigated with a co-culture consisting of Clostridium themocellum and Clostridium thermolacticum with or without immobilization. Alkali environments proved to be more favorable for ethanol production. Fermentation inhibition was observed at high ethanol concentrations (>8g/L) and extreme pH (>10). However, low levels of initial ethanol addition resulted in an unexpected stimulatory impact on the final ethanol productions for all cultures under selected conditions. The co-culture was able to actively ferment glucose, xylose, cellulose and micro-crystallized cellulose (MCC). The ethanol yield observed in the co-culture was higher (up to two-fold) than in mono-cultures, especially in MCC fermentation. The highest ethanol yield (as a percentage of the theoretical maximum) observed were 75% (w/w) for MCC and 90% (w/w) for xylose. Immobilization technique using sodium alginate is efficient in improve the ethanol production during co-culture fermentation, although the immobilization is not able to change the ethanol sensitivity of this co-culture. The ethanol yield through the use of immobilized technique increased to 97% of the theoretical efficiency for glucose. For cellobiose and MCC under optimized condition, the ethanol yields were approaching 85% of the theoretical efficiency. In order to examine the feasibility of this immobilization co-culture on lignocellulosic biomass conversion, untreated and pretreated aspen fermentations were performed. The immobilization co-culture shows clear benefit in bio-ethanol production in CBP process. With a 3h, 9% NaOH pretreatment, the aspen powder fermentation yield approached 78% of the maximum theoretical efficiency, which is almost twice the yield of the untreated aspen fermentation. Keywords: Consolidated bioprocessing, Clostridium sp., Fermentation, Co-culture, Lignocellulosic ethanol, Immobilization, Alginate gel.Item The effect of carbon inputs on microbial community structure and function: the role of fermentation processes in groundwater.(2009-12) Nelson, Denice KarenCarbon inputs to groundwater aquifers include intentional applications, as in bioremediation practices, and unintentional spills. The addition of carbon to an aquifer environment promotes the growth of a diverse and complex microbial community capable of generating several fermentation products, including some regulated compounds and methane, an explosive gas. This dissertation focuses on the fermentative community that develops in response to carbon application in an aquifer environment. Research was conducted to specifically examine 1) how fermentation processes affect partitioning of trichloroethene (TCE), a common groundwater contaminant, 2) the extent that continuous or pulsed carbon inputs affect microbial community structure and function, and 3) how an ethanol-based fuel (E85) stimulates fermentation processes, including methane generation, and the effect of ethanol toxicity on plume longevity. Remediation of groundwater plume source areas is challenging because lingering contaminants are often present as non-aqueous phase liquid (NAPL) and sorbed mass, and therefore difficult to remove via biodegradation or other commonly used remedial methods. Experimental results indicated that enhanced dissolution of TCE NAPL was possible through the addition and/or subsequent fermentation of a dilute molasses solution. Two mechanisms were responsible for the enhanced dissolution of NAPL; the addition of fresh molasses increased TCE solubility (>200%), thereby increasing the concentration gradient and subsequent mass transfer of NAPL to the dissolved phase, and mixing NAPL with fermented molasses solution significantly increased the surface area of the NAPL through formation of an emulsion, thereby increasing the mass flux of NAPL to the dissolved phase. In addition, the fermented liquid may have also decreased the soil partitioning coefficient (Kd) of TCE, indicating that enhanced transfer of sorbed mass to the aqueous phase could also occur in the presence of fermented molasses. These results can be used to optimize remedial systems to increase NAPL and sorbed-mass dissolution and are therefore important, particularly when bioremediation is used to polish residual source zones. The addition of organic carbon to a groundwater aquifer for biostimulation purposes promotes the growth of a diverse fermentative community as well as organisms targeted for contaminant degradation. Engineered carbon application systems commonly include either a continuous low dose of carbon, or periodic high doses of carbon. Experimental results indicated that a monthly pulse of a high dose (10% by volume) of molasses generated several fermentation products at high levels following each application, while a continuous feed of low molasses solution (0.4%) reached steady-state in 130 days, after which no further detection of fermentation products occurred. Methane generation in both systems was similar, indicating that methane production was not affected by the carbon addition strategy. Significant shifts in both Eubacteria and Archaea community structures were observed after carbon introduction, with the greatest changes correlating to the higher concentrations of carbon provided by the pulsed system. The total quantity of bacteria and methanogens was higher along the pulsed-fed column compared to the continuously-fed system. The continuously-fed column exhibited greater biofouling behavior. Taken together, biofouling did not appear to be a result of biomass quantity, rather a function of community structure. In summary, the method of carbon introduction (pulsed high-dose versus continuous low-dose) can result in significantly different community structures, functions, and densities of indigenous organisms. These data suggest that systems can be engineered to control fermentation product generation and biofouling behavior by manipulating the style of carbon application. Methane, however, will need to be controlled in either system. A spill of ethanol-based fuel will not only contaminate an aquifer, but will also serve as a food source to stimulate fermentative organisms that can generate potentially regulated compounds and create an environment conducive for production of explosive methane gas. Experimental results indicated that a continuous supply of a dilute ethanol-based fuel (E85) resulted in a profound shift in the community structure of Eubacteria and Archaea accompanied by the production of volatile fatty acids and butanol, a compound with a groundwater regulatory standard in Minnesota. Data also indicated that dissolved methane was produced at concentrations that could accumulate to an explosive level (>2 mg/L) in headspace. Quantitative polymerase chain reaction (qPCR) data showed a statistically significant increase in methanogenic populations, when compared to a control column. These results strongly correlated to areas of the column containing acetate, a breakdown product of ethanol. Toxicity data indicated that microbial growth was completely inhibited at approximately 6% (vol/vol) ethanol. These results suggest that even though ethanol is readily degradable, the core of an E85 spill may serve as a long-term source of contamination, and subsequent methane production, as it cannot be degraded until significant dilution has occurred. The research presented in this dissertation shows that the addition and subsequent fermentation of molasses can enhance the mass transfer of TCE, and that the style of carbon application affects the microbial community structure, density of biomass, and subsequent production of fermentation processes. Similarly, an input of E85 will result in the generation of fermentation products, some of which are regulated, and produce methane at levels that can potentially accumulate to explosive levels. This research furthers our understanding of the importance of fermentation processes resulting from carbon inputs to a groundwater environment. These results can be used to optimize bioremediation systems that incorporate carbon addition in order to manage fermentation product formation and biofouling impacts, and to mitigate potential human health hazards stemming from ethanol-based fuel spills through more accurate fate and transport modeling efforts.Item Effect of yeast, protected minerals and bismuth subsalicylate on in vitro fermentation by rumen microbes.(2012-04) Moreno, Martín RuizThree experiments were conducted using a dual flow continuous culture fermenter system. In Experiment I, two levels of active dry yeast at 0 or 2 mg/fermenter/day (NY and YS, respectively) were infused twice daily to fermenters in a completely randomized arrangement of treatments. Apparent and true OM digestion was not affected by yeast. No differences were obtained in NDF and ADF digestion. Total VFA concentrations were not affected by treatments. Addition of yeast did not affect VFA molar proportions or estimated CH4S production but resulted in a trend for a lower A:P ratio. Addition of yeast decreased NH3-N concentration and NH3-N daily flow, without affecting crude protein digestion and efficiency of microbial protein synthesis. Mean and minimum pH of fermenters did not differ between treatments but a trend for a lower maximum pH was obtained with yeast. In conclusion, a low dose of active dry yeast decreased NH3-N concentration and daily flow, without affecting any other of the in vitro rumen fermentation characteristics measured in this study. In Experiment II, effects of two levels of lignosulfonate and two sources of minerals (protected and unprotected) on rumen fermentation were evaluated using a 2 x 2 factorial arrangement of treatments. Addition of lignosulfonate tended to decrease daily flow of non NH3-N, efficiency of microbial protein synthesis, total VFA concentration and molar proportion of acetate, but increased molar proportion of propionate, valerate and caproate. Protected minerals decreased molar proportion of propionate. Addition of lignosulfonate increased ruminally soluble Cu and Mn, whereas protected minerals reduced ruminally soluble Cu. Concentrations of bacterial Cu and Zn increased with protected minerals in absence of lignosulfonate. Concentration of Mn was not affected by treatments. Addition of lignosulfonate resulted in higher enzymatic release of Zn from solids outflow but lower from bacterial pellets. Mean, minimum and maximum fermentation pH was higher with lignosulfonate, and not affected by mineral source. Addition of lignosulfonate induced major changes in ruminal fermentation. Protection of minerals decreased rumen soluble Cu and increased bacterial Cu and Zn without affecting postruminal release of minerals. In Experiment III, addition of bismuth subsalicylate (BSS) at 1% of DM and monensin (MON; 5 ppm) were used to assess their effects on rumen metabolism and H2S release by rumen microbes in a 2 x 2 factorial arrangement of treatments. Addition of BSS increased digestion of OM, NDF and ADF but decreased that of NFC and total VFA concentrations. Molar proportions of acetate and propionate increased with BSS in the diet, while that of butyrate decreased. Monensin decreased ADF digestion and A:P ratio, without affecting molar proportions of major VFA. Regarding nitrogen metabolism, MON increased non NH3-N outflow without affecting other measurements. Addition of BSS to the diet increased NH3-N concentration, NH3-N flow and dietary-N flow, while decreasing microbial-N outflow, CP digestion, and efficiency of microbial protein synthesis. Headspace H2S was reduced by 99% with BSS treatment but was not affected by MON. Only minor changes in fermentation pH were found with MON, but an increase in mean, minimum and maximum fermentation pH were found following addition of BSS. Results indicate that BSS can markedly reduce H2S production in short term and long term in vitro rumen incubations.Item Effects of bismuth subsalicylate and beta extract of hops (Humulus lupulus) on in vitro fermentation with ruminal microbes(2013-08) Fessenden, Samuel WilliamSymbiosis between microbes and ruminants gives the animal a unique ability to digest fiber and transform it into meat, milk, power and other useful products. Manipulation of rumen ecology with selective antimicrobial compounds can have beneficial effects by altering microbial output, allowing the animal to achieve greater levels of production per unit of input. Two experiments were conducted to determine effects of antimicrobial compounds on in vitro fermentation with ruminal microbes in continuous culture. Inclusion of bismuth subsalicylate decreased (P < 0.05) organic matter digestion, volatile fatty acid production and had negative influences on nitrogen and fatty acid metabolism. Results indicate that bismuth subsalicylate at 0.5% of diet dry matter was detrimental to overall fermentation with rumen microbes, and lower dosage levels should be investigated. In experiment 2, beta extract from the hop plant (Humulus lupulus) was administered to continuous culture fermenters at 0, 600, 1200 or 1800 mg of beta acids / kg of dry matter. Inclusion of beta extract did not affect (P > 0.05) ingredient digestion, volatile fatty acid production or nitrogen metabolism. Beta extract tended (P = 0.09) to increase culture pH, however effects were modest and lower than biologically relevant values. Further research investigating the adaptation of microbial populations to hop beta extract was recommended.Item Fungal Fermentation of Distillers Dried Grains with Solubles (DDGS) with Trichoderma reesei and Soybean Hull(2021) Gallant, Ethan T; Hu, Bo; Sun, XiaoThe main issue with utilizing DDGS as feeding ingredients for mono-gastric animals such as swine is its high concentration of fiber, phytate, and low levels of important amino acids, such as lysine, threonine, and methionine. To improve the utility of DDGS, the impact of solid-state fermentation on DDGS with the fungal strains, Trichoderma reesei (TR), Aspergillus oryzae (AO), and Mucor indicus (MI) was investigated. Results from experiments show fermenting DDGS and soybean hull with Trichoderma reesei and urea as the substrate for six days provides the best improvement in the amino acid profile and the most phytate and structural carbohydrate reduction. Fermentation DDGS and soybean hull with TR and urea produced a 56.84% increase in lysine, threonine, and methionine compared to the control samples analyzed. With TR and urea, phytate levels were reduced by 23.41%. Additionally, TR reduced the total carbohydrates in DDGS by 7.19% compared to TR and MI. TR and MI both produced the most amino acids with urea as the nitrogen source, while AO produced the most amino acids with ammonium nitrate as the nitrogen source. These results show the solid-state fermentation of DDGS and soybean hull with Trichoderma reesei and urea provide a significant improvement in the overall usefulness of the feed to livestock.