Browsing by Subject "Bioproducts and Biosystems Engineering"

Now showing 1 - 5 of 5
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    Comparison of Three Agricultural Residue-Based Filter Media for Use In a Denitrifying Bioreactor
    (2013-04-19) Slocum, Noah
    Denitrifying bioreactors are one possible solution to the problem of nitrate-nitrogen outflow from agricultural subsurface drainage to surface waters. This study was conducted to determine the effectiveness of a corn cob and wood chip mixture, comprised of an equal amount of each by weight, as a denitrifying bioreactor bed medium in comparison to both corn cobs and wood chips alone. The nitrate-nitrogen removal rates of these three media were tested by packing each into 15 cm by 50 cm PVC cylinders and pumping a solution with a 50 mg/L concentration of nitrate-nitrogen through them over a period of five months at a rate equivalent to a hydraulic resistance time of 12 hours. The entire apparatus was kept at 2˚ C as to imitate weather conditions common to Midwestern states in early spring. The average nitrate-nitrogen removal rates for the three media were: corn cob > mixture > wood chips.
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    Global Distribution of Wood-Decay Fungi: Patterns Without Predictability
    (2020) Traas, Jackson;
    There are three principal types of wood-degrading fungi: white-rot, brown-rot, and soft-rot. A basic role of wood-degrading fungi in forest ecosystems is to recycle the carbon stored by autotrophic organisms. Differences in the pathway through which each type of fungi degrades wood determines whether the carbon is released to the atmosphere as CO2, a greenhouse gas, or is recycled to the soil. Understanding the distribution and dominance of the different wood-decay fungi is pertinent to predicting their effect on the carbon cycle and a prerequisite for any type of mitigation strategy. Early theories attributed distribution to latitudinal geography based on correlative analysis. Attention then turned to the effects of climate, specifically moisture content and temperature, on this distribution. The prevailing theory is the connection between the wood substrate – either hardwood or softwood – and the fungal rot type, though recent evidence has called the absoluteness of this relationship into question. Current research is turning its focus to chemical growth factors of fungi such as nitrogen and phosphorous to see if these factors can explain rot type distribution. At present, many patterns between variables and distribution have been identified, but consistent counterexamples limit their predictability.
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    Improved Fermentation Through Removal of Acetic Groups for the Increased Production of Ethanol
    (2011-04-13) Frederick, Joseph
    Acetic groups have been known to reduce the production of ethanol during fermentation. Various chemical treatments were conducted on an artificial fermentation liquor in an attempt to reduce the amount of acetic groups in the solution. These treatments included calcium hydroxide and zeolites (aluminum and silicon structures). It was found that a zeolite with a silicon to aluminum ratio of 140 removed the most acetic groups (12.52%) and a zeolite with a silicon to aluminum ratio of 29 removed less (11.33%). However, the zeolite with the silicon to aluminum ratio of 29 managed to have a higher conversion of dextrose to ethanol than the zeolite with a silicon to aluminum ratio of 140.
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    Microscopic and thermal characterization studies of heterogeneous biocatalysis: polyurethane film immobilized enzymes and degradation of algal cells.
    (2011-07) Song, Wei
    Heterogeneous biocatalysis, associated with either solid-state biocatalyst systems or solid-state substrate systems, has garnered a lot of interest for chemical synthesis, bioseparation, and biosensing. In the pursuit of high efficiency, the characterization of the physical structure of solid-state biocatalysts and solid-state substrates is necessary to provide detailed information and deepen the understanding for the heterogeneous biocatalytic systems. In this study, microscopic and thermal analytical methods were utilized to characterize the physical structure of solid-state biocatalysts and solid-state substrates. Particularly, we chose the versatile polymer polyurethane (PU) to immobilize enzymes as model solid-state biocatalysts. Two important physical properties, enzyme distribution and glass transition temperature (Tg), were analyzed. It was found that several preparation parameters, including hydrophobic/hydrophilic properties of resin and cross-linker for PU film, weight ratio of starting materials, and mixing speed, showed significant influences on enzyme distribution and Tg. Using microscopic and thermal characterization methods, we further studied the integrity of enzyme-containing PU film against water. The enzyme was found prone to leak from the PU film, indicating incompleteness of cross-linking with PU. Several approaches (e.g., increasing the reaction time and using a hydrophilic cross-linker) were explored in this work to promote better cross-linking between the enzyme and PU matrix. The hydrophilic cross-linker (Bayhydur 302) demonstrated 70% improvement in retaining the enzyme against 24 hours of washing compared to a hydrophobic cross-linker (DESMOPHEN N3600). Moreover, algae cells were studied as model solid-state substrates. We report a novel enzymatic method to disrupt the cell wall and release lipids from the algae cells. Microscopic analysis indicated that the cell wall of Chlamydomonas reinhardtii (C.R.) algae was disrupted after being treated by a three-step method, which included one hour of incubation in 4 M of lithium chloride, eight hours of hydrolytic reaction in enzyme solution, and one cycle of freeze/thaw process. Protease Subtilisin Carlsberg was found effective in catalyzing the degradation of C.R. cell wall due to its unspecific activity toward peptide bonds.
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    Raman spectroscopic studies of load transfer in microfibrillated cellulose/poly(Lactic acid) composites.
    (2011-07) Yao, Jin
    The objective of this research was to investigate the feasibility of using Raman-tensile tests to evaluatethe transfer of load between polylactic acid (PLA) and cellulose nanofibers. Microfibrillated cellulose (MFC) was modified with oligomeric lactic acid. The modified MFC was loaded into a PLA solution before being cast into a film. The nanocomposite films were subjected to tensile loading during which Raman spectroscopy was performed under a microscope. The Raman spectrum of MFC was isolated from the spectrum of its composites. The stress-sensitive Raman band of cellulose (1095 cm-1) was analyzed for wavenumber shift, which is an indication of load transfer from the PLA matrix to MFC. Compared to the control (untreated) sample, composites with lactide-treated MFC exhibited a higher Raman band shift as a response to both applied strain and stress, indicating an improved efficiency of load transfer across the compatibilized interphase between nanofibers and PLA. The effect of MFC addition ratio on the load transfer ability was also discussed. A higher MFC weight fraction (0.5 % versus 0.25 %) in the composite did not significantly affect the load transfer efficiency. This finding suggests that the efficiency of matrix/fiber load transfer at the local level is independent of the effects of macroscopic fiber-to-matrix ratio, at least at the (low) levels of MFC loading examined in this study. Overall, this research shows that it is feasible to use Raman spectroscopy to monitor load transfer in MFC/PLA composites for examining strategies aimed at improving adhesion and knowledge of the mechanism of PLA reinforcement by nano-cellulose.