Thesis (Ph. D. in Mathematics)--Vanderbilt University, Dec. 2005. / Title from title screen. Includes bibliographical references.

Thesis (PhD) - Environment and Biotechnology Centre, Faculty of Life and Social Sciences, Swinburne University of Technology, 2008. / Submitted for the degree of Doctor of Philosophy, Environment and Biotechnology Centre, Faculty of Life and Social Sciences, Swinburne University of Technology, 2008. Typescript. Includes bibliographical references (p. 215-247)

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Thesis (M.Sc. (Microbiology)) -- University of Limpopo, 2020 / Bioethanol production from lignocellulosic biomass is seen as an alternative source of energy. However, large-scale production of bioethanol from lignocellulosic biomass is still not feasible due to the high cost of cellulase and lack of cellulases with a high specific activity that can act on crystalline cellulose. The study aimed at screening for microbial cellulolytic enzymes using a proteomic approach. The objectives were to screen for microbial cellulases with a high specific activity and separate the cellulolytic enzymes using a combination of zymography and two dimensional (2-D) gel electrophoresis followed by tryptic digestion, matrix assisted laser desorption ionisation-time of flight (MALDI-TOF) and bioinformatics analysis. Fungal and bacterial isolates were cultured in M9 minimal and Mandel media for a period of 168 hours at 60°C and 30°C with cellobiose and Avicel as carbon sources. Microbial cells were separated from the supernatants through centrifugation and the crude enzymes from the cultures were used for the determination of cellulase activity, zymography, SDS-PAGE and two-dimensional gel electrophoresis. Five isolates, with lytic action on carbon sources studied were a bacterial strain, (BARK) and fungal strains (VCFF1, VCFF14, VCFF17 and VCFF18). Peak cellulase production by the isolates was found to be 3.8U/ml, 2.09U/ml, 3.38U/ml, 3.18U/ml and 1.95U/ml, respectively. Beta-glucosidase zymography resulted in a dark brown band and clear zones against a dark background for endoglucanase. Affinity precipitation of the VCFF17 isolate’s crude enzyme resulted in seven glycoside hydrolases with a carbohydrate binding module (CBM). The presence of the CBM in the glycoside hydrolases produced by the VCFF17 confer the isolate’s potential to be used in the hydrolysis of plant biomass for bioethanol production. Two-dimensional gel protein maps resulted in the separation and quantitative expression of different proteins by the microbial isolates. MALDI-TOF analysis and database search showed that the expressed proteins in this study closely relate to different glycoside hydrolases produced by other microbial species (Hypocrea jecorina, Emericella nidulans, Trichoderma pseudokoningii and Trichoderma koningii). BARK, VCFF1, VCFF14, VCFF17 and VCFF18 showed great potential as cellulolytic enzyme producers for bioethanol production. The BARK isolate exhibited the highest beta glucosidase activity. The isolates studied may benefit the industry in reducing the costs associated with bioethanol production in consolidated bioprocessing system. / National Research Foundation (NRF)

<p> A novel mathematical model has been developed for biofilms and bioflocs. The model is based on the use of the effectiveness factor and the effect of cell density is included. The key assumption in the model is that cell density decreases in proportion to the substrate concentration within the biofilm or biofloc, reflecting lower rates of cellular metabolism. The equations given by the model were solved numerically for three types of reaction kinetics: Monod, Andrews (substrate inhibition), and multiple-Monod (twolimiting substrates), as well as for two geometries: a slab, as a representation of a biofilm and a sphere, as a representation of a biofloc. The simulations indicate that a decrease of the cell density in the biofilm and biofloc results in a decline of the effectiveness factor. Furthermore, the analytical solutions and approximate analytical versions of the effectiveness factor for the biofilm in two cell growth models: Monod and Andrews, have been derived. The effectiveness factors derived analytically are in agreement with those calculated numerically, and the approximate analytical versions are valid for the Thiele modulus greater than five. This new model was tested using operational data available in the literature, by including the effectiveness factor as a part of the design equations for an upflow anaerobic sludge blanket (UASB) reactor. </p> <p> For any biologically mediated transformation, it is critical to uniquely identify the parameters associated with microbial growth models. In this study, it is proved that the parameters of the integrated Andrews model are identifiable if the experimental data does not contain any random noise based on a criterion proposed by Beck and Arnold [1977]. When noise is present, the parameters may or may not be identifiable, depending on noise levels. A new approach has been developed based on the calculation of dimensionless sensitivity coefficients. Plotting these coefficients provides straightforward visualization of parameter identification. This method was used for quantitative evaluation of the noise level that can be associated with measurements, while still allowing parameter identification. It was demonstrated that an indirect cause of the parameter nonidentification of the integrated Andrews model is the linearization of the Andrews model at a low or high substrate concentration. Robinson [1985] obtained a similar result with the Monod model. </p> / Thesis / Master of Science (MSc)

A numerical model for subsurface solute transport is developed and applied to a contaminated field site. The model is capable of depicting multiple species transport in a three-dimensional, anisotropic, heterogeneous domain as influenced by advection, dispersion, adsorption, and biodegradation. Various hydrocarbon contaminants are simulated as electron donors for microbial growth, with electron acceptors utilized in the following sequence: oxygen, nitrate, Mn(IV), Fe(III), sulfate, and CO₂. In addition, the model accounts for products of biodegradation such as Mn (II), Fe(II), H₂S, and CH₄. Biodegradation of each hydrocarbon substrate follows Monod kinetics, modified to include the effects of electron acceptor and nutrient availability. Inhibition functions permit any electron acceptor to inhibit utilization of all other electron acceptors that provide less Gibbs free energy to the microbes. The model assumes that Fe(III) and Mn(IV) occur as solid phase ions, while the other electron acceptors are dissolved in the aqueous phase. Microbial biomass is simulated as independent groups of heterotrophic bacteria that exist as scattered microcolonies attached to the porous medium. Diffusional limitations to microbial growth are assumed to be negligible. In order to verify the accuracy of the computer code, the model was applied to simple, hypothetical test cases, and the results were compared to analytical solutions. In addition, a sensitivity analysis showed that variations in model inputs caused logical changes in output. Finally, the capabilities of the model were tested by comparing model output to observed concentrations of hydrocarbons, electron acceptors, and endproducts at a leaking UST site. The model was calibrated using historical site data, and predictive capabilities of the model were tested against subsequent sets of field data. The model was used to examine the effect of porous media heterogeneities on contaminant transport and biodegradation. The turning bands method was used to produce hypothetical, yet realistic heterogeneous fields describing hydraulic conductivity, initial biomass concentration, and the maximum rate of substrate utilization. When the available electron acceptor concentrations were small compared to the hydrocarbon concentration, the overall rate of hydrocarbon mass loss increased with time, even as hydrocarbon concentrations decreased. This trend is the opposite of what would be predicted by a first order decay model. / Ph. D.

An interaction of the commensalism type between P. vulgais and S. cerevisiae was discovered and verified. A continuous flow apparatus for investigation of this interaction was described. A Coulter Counter was used for detecting the number of the microorganisms grown in mixed cultures. Size distribution curves were prepared and used as a means for determining the Coulter Counter settings for counting each organism. Coulter Counter counts were compared with Petroff-Hausser counts; the results showed approximately 20 per cent discrepancy which is reasonable since the Petroff-Hausser method is quite crude. P. vulgaris in mixed culture and in the media of Table I was shown to be completely dependent upon S. cerevisiae. S. cerevisiae was found to be unaffected by P. vulgaris, thus, the definition of commensalism is fully satisfied. The search for the biochemical causing this interaction led to the trial of the following: 1 per cent yeast extract, 0.01 per cent DPN, 1 per cent Nicotinamide, and 0.01 per cent Niacin; all sterilized by filtration. The slug addition of these biochemicals to the culture vessels caused the P. vulgaris to be independent of the S. cerevisiae. As a result, Niacin or near biochemical relatives are believed to be the essential compounds causing the interaction between P. vulgaris and S. cerevisiae. The steady state population of the P. vulgaris was found to increase with Niacin concentration up to a certain limit above which further Niacin has no effect. The concentration of Niacin-like activity formed per yeast cell was also calculated; this concentration per yeast cell was found to vary with the flow rate. Concentration of the media and aeration were also found to have an effect on the steady state populations. Inoculating cultures of S. cerevisiae with a faster growing bacterium, E. coli, showed E. coli increasing in number until it reached a steady state while S. cerevisiae decreased in number to a null value. This result was in agreement with that predicted by published theories of contamination, Golle (1953). / Ph. D.

This study compared the effects of 1.4 or 2.7% sodium levulinate or sodium lactate on aerobic plate count (APC), color, pH, and TBA value of fresh pork and turkey sausage. Both sodium lactate and Jevulinate inhibited growth of aerobic microorganisms during storage, compared to controls. Bacteriostatic effects of sodium lactate were dose dependent, wherein 2.7% lactate was significantly more antimicrobial than 1.4% lactate. This was not the case for sodium levulinate, where 1.4% sodium levulinate was as inhibitory to microbial growth as 2.7% sodium levulinate. Additionally, 1.4% sodium levulinate was as inhibitory to microbial growth as the higher level (2.7%) of sodium lactate. TBA values, color, and pH were not affected by treatment with sodium lactate or levulinate. In conclusion, sodium levulinate may have potential as an antimicrobial agent in fresh sausages if it can be obtained at a reasonable cost on a commercial basis.

<p>For produced biogas to be usable as vehicle fuel it has to be upgraded to a higher energy content. This is accomplished by elevation of the methane concentration through removal of carbon dioxide. Absorption with water wash is the most common upgrading method used in Sweden today. The upgrading technique is based on the fact that carbon dioxide is more soluble in water than methane. Upgrading plants that utilises this method have problems with microbial growth in the system. This growth eventually leads to a stop in operation due to the gradually drop in upgrading capacity.</p><p>The aim of this thesis were to evaluate the possibility to through some kind of water treatment maintain an acceptable level of growth or altogether prevent it in order to maintain an acceptable process capacity and thereby avoid the need to clean. Through collection of literature the implementation possibilities were evaluated with regard to efficiency, economic sustainability and if there would be a release of any harmful substances.</p><p>In order to prevent the microbial growth in the columns the treatment should either focus on removing microorganisms or limit the accessible nutrients. For the single pass system it is concluded that the treatment should reduce the biofilm formation and be employed in an intermittent way. Among the evaluated treatments focusing on the reduction of microorganisms the addition of peracetic acid seems to be the most promising one. For the regenerating system the treatment method could focus on either one. As for the single pass system peracetic acid could be added to reduce the amount of microorganism. To reduce the amount of organic matter an advanced oxidation process could be deployed with the advantage that it also could remove the microorganisms.</p> / <p>För att kunna använda den producerade biogasen som fordonsgas måste dess energiinnehåll höjas. Detta åstadkoms genom avskiljning av koldioxid så att metankoncentrationen ökar. Den vanligaste förekommande uppgraderingstekniken i Sveriges är absorption med vatten, som bygger på att koldioxid är mer lösligt än metan i vatten under tryck. Uppgraderingsanläggningarna har mikrobiell tillväxt på fyllkropparna i absorptionskolonnen, vilket ofrånkommligen orsakar en lägre uppgraderingskapacitet och slutligen är ett stopp i produktionen nödvändig för kunna tvätta fyllkropparna. Anläggningarna som recirkulerar processvattnet kan även ha tillväxt i kolonnen, där den lösta koldioxiden tas bort.</p><p>Syftet med detta arbete var att genom en litteraturstudie undersöka om det vore möjligt att undvika eller åtminstone hålla tillväxten under en acceptabel nivå genom någon typ av vattenrening. De olika reningsmetoderna utvärderades med avseende på möjlighet att implementeras i det befintliga uppgraderings systemet, effektivitet, möjliga utsläpp och ekonomisk hållbarhet.</p><p>För att begränsa tillväxt i kolonnerna ska vattenreningen antingen fokusera på att ta bort mikroorganismer eller begränsa tillgången på näringsämnen för bakterierna som når kolonnerna via biogasen, luften som används för att ta bort koldioxiden från vattnet, eller via vattnet. För uppgraderingsanläggningar där processvattnet bara passerar kolonnen en gång rekommenderas en reningsmetod som fokuserar på reducera bildandet av biofilmen. Av de utvärderade metoderna ter sig perättiksyra som det bästa alternativet. För system med recirkulerande processvatten skulle reningsmetoden fokusera på antingen reduktion av mikroorganismer, organiskt material eller både och. Som för anläggningar med icke-cirkulerande vatten verkar perättiksyra vara det bästa alternativet för reduktion av mikroorganismer. En avancerad oxidationsprocess skulle kunna användas för att reducera mängden mikroorganismer och organiskt material.</p>

Sustainable polymeric materials put emphasis on mastering the whole life-cycle of polymeric materials. This includes the choice of raw materials, selection of synthesis and processing, environmental impact during long-term use followed by detailed knowledge about recycling and waste management.  Within this large efforts are put in the design and development of new biocomposites using renewable fibres instead of inert ones. The thesis deals with surface modifications of agricultural fibres and the design of biocomposites with optimal long-term properties balancing the potential risk for biodegradation.  The first part of this thesis involved surface modifications of oil palm fibres and production of biocomposites with PP as matrix. The chemical surface modifications of oil palm fibres explored propionylation, PPgMA grafting via solution modification and reactive blending and vinyltrimethoxy silanization as methods. All modified fibre/PP biocomposites showed improvements in the mechanical properties followed also by an improvement of water resistance. In comparison with unmodificed fibres/PP matrix the highest water resistance after the surface modifications of oil palm fibres were observed for silanization followed by PPgMA modified,  PPgMA blending and  propionylation. The second part aimed at producing fully biodegradable biocomposites and analysing the resulting properties with respect to potential risk for biodegradation. Sisal fibres were incorporated in PLA and PHBV and the resulting risk for biodegradation using a fungus, Aspergillus niger, monitored. Neat PLA and PHBV were compared with the corresponding biocomposites and already without fibres both polymers were notably biodegraded by Aspergillus niger. The degree of biodegradation of PLA and PHBV matrices was related to the extent of the growth on the material surfaces. Adding sisal fibres gave a substantial increase in the growth on the surfaces of the biocomposites. Correlating the type of surface modification of sisal fibres with degree of biodegradation, it was demonstrated that all chemically modified sisal/PLA biocomposites were less biodegraded than unmodified sisal biocomposites.  Propionylated sisal/PLA demonstrated the best resistance to biodegradation of all biocomposites while sisal/CA/PLA demonstrated high level of biodegradation after severe invasion by Aspergillus niger. In general, the biodegradation correlated strongly with the degree of water absorption and surface modifications that increase the hydrophobicity is a route to improve the resistance to biodegradation. Designing new biocomposites using renewable fibres and non-renewable and renewable matrices involve the balancing of the increase in mechanical properties, after improved adhesion between fibres and the polymer matrix, with the potential risk for biodegradation. / <p>QC 20130325</p>