Dry-cured hams may become infested with Tyrophagus putrescentiae (ham mites) during the aging process. Traditionally, methyl bromide (MB) fumigation has been used to control these infestations, but its phase-out due to environmental concerns has prompted the need for alternative methods. This study evaluated the effectiveness of acetic acid-coated ham nets and carboxymethyl cellulose (CMC)-based edible films with propylene glycol (PG) in mitigating mite infestations. Laboratory trials assessed the impact of these treatments on mite orientation, reproduction, infestation rates, and sensory quality. Results indicate that CMC films were effective at controlling mite growth and reproduction with minimal sensory impact. In contrast, acetic acid-coated nets offered some deterrence but failed to substantially control mite populations. This research suggests that CMC films with PG may be a viable and sustainable alternative to MB fumigation, though further testing is needed to verify that it is effective when commercially upscaled.

This thesis deals with the preparation of chemically and/or enzymatically modified cellulose. This modification can be either irreversible or reversible. Irreversible modification is used to prepare cellulose derivatives as end products, whereas reversible modification is used to enhance solubility in the preparation of regenerated cellulose. The irreversible modification studied here was the preparation of carboxymethyl cellulose (CMC) using extended mercerization of a spruce dissolving pulp. More specifically the parameters studied were the effect of mercerization at different proportions of cellulose I and II in the dissolving pulp, the concentration of alkali, the temperature and the reaction time. The parameters evaluated were the degree of substitution, the filterability and the amount of gel obtained when the resulting CMC was dissolved in water. Molecular structures of CMC and its gel fractions were analysed by using NIR FT Raman spectroscopy. It was found that the alkali concentration in the mercerization stage had an extensive influence on the subsequent etherification reaction. FT Raman spectra of CMC samples and their gel fractions prepared with low NaOH concentrations (9%) in the mercerization stage indicated an incomplete transformation of cellulose to Na-cellulose before carboxymethylation to CMC. Low average DS values of the CMC, i.e. between 0.42 and 0.50 were obtained. Such CMC dissolved in water resulted in very thick and semi solid gum-like gels, probably due to an uneven distribution of substituents along the cellulose backbone. FT Raman spectra of CMC samples and their gel fractions mercerized at higher alkaline concentration, i.e. 18.25 and 27.5% in the mercerization stage, indicated on the other hand a complete transformation of cellulose to Na-cellulose before carboxymethylation to CMC. Higher average DS values of the CMC, i.e. between 0.88 and 1.05 were therefore obtained. When dissolved in water such CMC caused gel formation especially when prepared from dissolving pulp with a high fraction of cellulose II. The reversible modification studied was the dissolution of cellulose in NaOH/ZnO. Here the effect of enzyme pretreatment was investigated by using two mono-component enzymes; namely xylanase and endoglucanase, used in consecutive stages. It was found that although the crystallinity and the specific surface area of the dissolving pulp sustained minimal change during the enzymatic treatment; the solubility of pulp increased in a NaOH/ZnO solution from 29% for untreated pulp up to 81% for enzymatic pretreated pulp. / Baksidetext Cellulose can be chemically and/or enzymatically modified. Irreversible modification is used to prepare cellulose derivatives as end products, reversible modification to enhance solubility in the preparation of regenerated cellulose. The irreversible modification studied here was the preparation of carboxymethyl cellulose (CMC) using extended mercerization of a spruce dissolving pulp. More specifically the parameters studied were the effect of mercerization at different proportions of cellulose I and II in the dissolving pulp, the concentration of alkali, the temperature and the reaction time. It was found that the alkali concentration in the mercerization stage had an extensive influence on the subsequent etherification reaction. The content of cellulose II had little effect on degree of substitution (DS) at low NaOH concentration, but tended to decrease DS at higher NaOH concentration in both cases compared with cellulose I. It was also found that the content of cellulose II correlates with the gel formation obtained when the CMC is dissolved in water. The reversible modification studied was the dissolution of cellulose in NaOH/ZnO. Here the effect of enzyme pretreatment was investigated by using two mono-component enzymes; namely xylanase and endoglucanase, used in consecutive stages. It was found that the solubility of pulp increased in a NaOH/ZnO solution from 29% for untreated pulp up to 81% for enzymatic pretreated pulp.

Cellulose nanofibrils (CNFs) are nanoscale fibers of high aspect ratio that can be isolated from a wide variety of cellulosic sources, including wood and bacterial cellulose. With high strength despite of their low density, CNFs are a promising renewable building block for the preparation of nanostructured materials and composites. To fabricate CNF-based materials with improved inherent rheological and mechanical properties and additional new functionalities, it is essential to tailor the surface properties of individual CNFs. The surface structures control the interactions between CNFs and ultimately dictate the structure and macroscale properties of the bulk material. In this thesis we have demonstrated different approaches, ranging from non-covalent adsorption and covalent chemical modification to modification of cellulose biosynthesis, to tailor the structure and surface functionalities of CNFs for the fabrication of advanced materials. These materials possess enhanced properties such as water-redispersibility, water absorbency, dye adsorption capacity, antibacterial activity, and mechanical properties. In Paper I, CNFs were modified via the irreversible adsorption of carboxymethyl cellulose (CMC). The adsorption of small amounts of CMC onto the surface of CNFs prevented agglomeration and co-crystallization of the nanofibrils upon drying, and allowed the recovery of rheological and mechanical properties after redispersion of dried CNF samples. In Paper II, CNFs bearing permanent cationic charges were prepared through quaternization of wood pulp fibers followed by mechanical disintegration. The activation of the hydroxyl groups on pulp fibers by alkaline treatment was optimized prior to quaternization. This optimization resulted in individual CNFs with uniform width and tunable cationic charge densities. These cationic CNFs demonstrated ultrahigh water absorbency and high adsorption capacity for anionic dyes. In Paper III, via a similar approach as in Paper II, CNFs bearing polyethylene glycol (PEG) were prepared by covalently grafting PEG to carboxylated pulp fibers prior to mechanical disintegration. CNFs with a high surface chain density of PEG and a uniform width were oriented to produce macroscopic ribbons simply by mechanical stretching of the CNF hydrogel network before drying. The uniform grafted thin monolayer of PEG on the surface of individual CNFs prevented the agglomeration of CNFs and facilitated their alignment upon mechanical stretching, thus resulted in ribbons with ultrahigh tensile strength and modulus. These optically transparent ribbons also demonstrated interesting biaxial light scattering behavior. In Paper IV, bacterial cellulose (BC) was modified by the addition of chitin nanocrystals (ChNCs) into the growing culture medium of the bacteria Acetobacter aceti which secretes cellulose in the form of entangled nanofibers. This led to the in situ incorporation of ChNCs into the BC nanofibers network and resulted in BC/ChNC nanocomposites exhibiting bactericidal activity. Further, blending of BC nanofibers with ChNCs produced nanocomposite films with relatively lower tensile strength and modulus compared to the in situ cultivated ones. The bactericidal activity increased significantly with increasing amount of ChNCs for nanocomposites prepared by direct mixing of BC nanofibers and ChNCs. In Paper V, CNFs were isolated from suspension-cultured wild-type (WT) and cellulose-binding module (CBM) transformed tobacco BY-2 (Nicotiana tabacum L. cv bright yellow) cells. Results from strong sulfuric acid hydrolysis indicated that CNFs from transgenic cells overexpressing CBM consisted of longer cellulose nanocrystals compared to CNFs from WT cells. Nanopapers prepared from CNFs of transgenic cells demonstrated significantly enhanced toughness compared to CNFs of WT cells. / <p>QC 20141103</p> / CARBOMAT

Ce travail est une contribution expérimentale à l'étude rhéologique et en écoulement de fluides complexes (à seuil et thixotropes) transitant dans un circuit hydraulique. Il s'agit notamment de suspensions de bentonite ainsi que des complexes bentonite/polymère. L'étude porte sur l'évolution des pertes de charge et des champs de vitesse et se situe en régime laminaire, transitoire et turbulent. L'étude a été réalisée en utilisant un vélocimètre ultrasonore Doppler pulsé développé au laboratoire. Dans la première partie expérimentale de la thèse, des mesures rhéologiques et en écoulement ont été effectuées sur des suspensions de bentonite pures (sans additifs) à différentes concentrations. A partir des essais sur boucle hydraulique, une étude détaillée est présentée sur l'évolution des coefficients de frottement et des profils de vitesse pour les différents régimes d'écoulement. Dans une seconde partie, une suspension de bentonite pure et des mélanges bentonite/CMC à différentes concentrations massiques ont été étudiées en termes de comportement rhéologique et hydrodynamique en écoulement en conduite. En ce qui concerne les mesures effectuées en boucle hydraulique, il a été montré que le polymère a des propriétés viscosifiantes en régime laminaire. Par contre, en régime turbulent, le polymère agit comme un réducteur de frottement. La dernière partie de la thèse a été consacrée à l'étude de l'influence de la température sur le comportement rhéologique des solutions de polymère et des mélanges argile/polymère. Les mesures rhéologiques à différents paliers de températures ainsi que les balayages en température ont mis en évidence le caractère thermodépendant des dispersions.

Thesis (DTech (Electrical Engineering))--Cape Peninsula University of Technology, 2011 / Ultrasonic Velocity Profiling (UVP) is both a method and a device to measure an instantaneous one-dimensional velocity profile along a measurement axis by using Doppler echography. UVP is an ideal technique since it is non-invasive, works with opaque systems, inexpensive, portable and easy to implement relative to other velocity profile measurement methods. Studies have suggested that the accuracy of the measured velocity gradient close to wall interfaces need to be improved. The reason for this is due to, depending on the installation method, distortion caused by cavities situated in front of ultrasonic transducers, measurement volumes overlapping wall interfaces, refraction of the ultrasonic wave as well as sound velocity variations. A new ultrasonic transducer, which incorporates a delay line material optimised for beam forming could reduce these problems (Wiklund, 2007). If these could be addressed, UVP could be used for the measurement of velocity profiles in complex geometries (e.g. contractions, valves, bends and other pipe fittings) where the shape of the velocity profile is critical to derive models for estimating fluid momentum and kinetic energy for energy efficient designs. The objective of this research work was to optimise the UVP system for accurate complex flow measurements by evaluating a specially designed delay line transducer and implementing advanced signal processing techniques. The experimental work was conducted at the Material Science and Technology (MST) group at the Cape Peninsula University of Technology (CPUT). This work also formed part of a collaborative project with SIK - The Swedish Institute for Food and Biotechnology. Acoustic characterisation of the ultrasonic transducers using an advanced robotic setup was done at SI K. Different concentrations of the following non-Newtonian fluids exhibiting different rheological characteristics were used for testing: carboxymethyl cellulose (CMC) solutions, kaolin and bentonite suspensions. Water was used for calibration purposes.

Forward osmosis (FO) is an emerging technology for water treatment due to their ability to draw freshwater using an osmotic pressure gradient across a semi-permeable membrane. However, the lack of draw agents that could both produce reasonable flux and be separated from the draw solution at a low cost stand in the way of widespread implementation. This study had two objectives: evaluate the performance of three materials — peptone, carboxymethyl cellulose (CMC), and magnetite nanoparticles (Fe3O4 NPs) — as potential draw agents, and to use multi-criteria decision matrices to systematically prioritize known draw agents from literature for research investigation. Peptone showed water flux and reverse solute flux values comparable to other organic draw agents. CMC’s high viscosity made it impractical to use and is not recommended as a draw agent. Fe3O4 NPs showed average low fluxes (e.g., 2.14 LMH) but discrete occurrences of high flux values (e.g., 14 LMH) were observed during FO tests. This result indicates that these nanoparticles have potential as draw agents but further work is needed to optimize the characteristics of the nanoparticle suspension. Separation of the nanoparticles from the product water using coagulation was shown to be theoretically possible if only electrostatic and van der Waals forces are taken into account, not steric repulsion. If coagulation is to be considered for separation, research efforts on development of nanoparticle suspensions as FO draw agents should focus on development of electrostatically stabilized nanoparticles. A combination of Fe3O4 NP and peptone showed a higher flux than Fe3O4 NPs alone, but did not produce additive or synergistic flux. This warrants further research to investigate more combinations of draw agents to achieve higher flux than that obtained by individual draw agents. Potential draw agents were prioritized by conducting a literature review of draw agents, extracting data on evaluation criteria for draw agents developed over the past five years, using these data to rank the draw agents using the Analytical Hierarchy Process (AHP) and Technique for Order of Preference by Similarity to Ideal Solutions (TOPSIS). The evaluation criteria used in the ranking matrices were water flux, reverse solute flux, replenishment cost, regeneration cost, and regeneration efficacy. The results showed that the top five ranked draw agents were P-2SO3-2Na, TPHMP-Na, PEI-600P-Na, NaCl, and NH4-CO2. The impact of the assumption made during the multi-criteria decision analysis process was evaluated through sensitivity analyses altering criterion weighting and including more criteria. This ranking system provided recommendations for future research and development on draw agents by highlighting research gaps.

>Magister Scientiae - MSc / Glucose oxidase (GOx) and horseradish peroxidase (HRP) are important enzymes for the development of amperometric enzyme linked immunosensors. The selectivity of each enzyme towards its analyte deepens its importance in determining the sensitivity of the resultant immunosensor. In designing immunosensors that have customized transducer surfaces, the incorporation with FAD and iron based enzymes ensures that electron kinetics remains optimal for electrochemical measurement. Various different immobilization strategies are used to produce response signals directly proportional to the concentration of analyte with minimal interferences. The combination of self-assembled monolayers and supramolecular chemistry affords stability and simplicity in immunosensor design. In this work, two electrochemical strategies for the detection of human chorionic gonadotropin(hCG) is presented. This involves the modification of a gold surface with a thiolated β-cyclodextrin epichlorohydrin polymer (βCDPSH) to form a supramolecular inclusion complex with ferrocene (Fc)-functionalised carboxymethyl cellulose polymer (CMC). Cyclic voltammetry indicated that ferrocene is in close proximity to the electrode surface due to the supramolecular complex formed with βCDPSH. Furthermore, strategy (a) for the detection of hCG used α-antihCG labelled (HRP) as reporter conjugate. Strategy (b) maintained the CMC bifunctionalised with Fc and recognition antibody for hCG hormone. However, the system was functionalised with a HRP enzyme and detection is done by using GOx reporter conjugates for in situ production of hydrogen peroxide. The reduction of H2O2 was used for the amperometric detection of hCG by applying a potential of 200 mV. The sensitivity and limit of detection of both strategies were calculated from calibration plots. For strategy (a) the LOD was found to be 3.7283 ng/mL corresponding to 33.56 mIU/mL and a sensitivity of 0.0914 nA ng-1 mL-1. The corresponding values for strategy (b) are 700 pg/mL (6.3 mIU/mL) and 0.94 nA ng-1 mL-1.

Made available in DSpace on 2014-12-17T15:42:31Z (GMT). No. of bitstreams: 1 BrunaVL_TESE.pdf: 4965695 bytes, checksum: f511eb063b5cd567f364bc0ec9385727 (MD5) Previous issue date: 2014-05-28 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / Sustainable development is a major challenge in the oil industry and has aroused growing interest in research to obtain materials from renewable sources. Carboxymethylcellulose (CMC) is a polysaccharide derived from cellulose and becomes attractive because it is water-soluble, renewable, biodegradable and inexpensive, as well as may be chemically modified to gain new properties. Among the derivatives of carboxymethylcellulose, systems have been developed to induce stimuli-responsive properties and extend the applicability of multiple-responsive materials. Although these new materials have been the subject of study, understanding of their physicochemical properties, such as viscosity, solubility and particle size as a function of pH and temperature, is still very limited. This study describes systems of physical blends and copolymers based on carboxymethylcellulose and poly (N-isopropylacrylamide) (PNIPAM), with different feed percentage compositions of the reaction (25CMC, 50CMC e 75CMC), in aqueous solution. The chemical structure of the polymers was investigated by infrared and CHN elementary analysis. The physical blends were analyzed by rheology and the copolymers by UV-visible spectroscopy, small-angle X-ray scattering (SAXS), dynamic light scattering (DLS) and zeta potential. CMC and copolymer were assessed as scale inhibitors of calcium carbonate (CaCO3) using dynamic tube blocking tests and chemical compatibility tests, as well as scanning electron microscopy (SEM). Thermothickening behavior was observed for the 50 % CMC_50 % PNIPAM and 25 % CMC_75 % PNIPAM physical blends in aqueous solution at concentrations of 6 and 2 g/L, respectively, depending on polymer concentration and composition. For the copolymers, the increase in temperature and amount of PNIPAM favored polymer-polymer interactions through hydrophobic groups, resulting in increased turbidity of polymer solutions. Particle size decreased with the rise in copolymer PNIPAM content as a function of pH (3-12), at 25 ?C. Larger amounts of CMC result in a stronger effect of pH on particle size, indicating pH-responsive behavior. Thus, 25CMC was not affected by the change in pH, exhibiting similar behavior to PNIPAM. In addition, the presence of acidic or basic additives influenced particle size, which was smaller in the presence of the additives than in distilled water. The results of zeta potential also showed greater variation for polymers in distilled water than in the presence of acids and bases. The lower critical solution temperature (LCST) of PNIPAM determined by DLS corroborated the value obtained by UV-visible spectroscopy. SAXS data for PNIPAM and 50CMC indicated phase transition when the temperature increased from 32 to 34 ?C. A reduction in or absence of electrostatic properties was observed as a function of increased PNIPAM in copolymer composition. Assessment of samples as scale inhibitors showed that CMC performed better than the copolymers. This was attributed to the higher charge density present in CMC. The SEM micrographs confirmed morphological changes in the CaCO3 crystals, demonstrating the scale inhibiting potential of these polymers / O desenvolvimento sustent?vel ? um dos principais desafios da ind?stria do petr?leo, que tem despertado crescente interesse por pesquisas para obten??o de novos materiais provenientes de fontes renov?veis. A carboximetilcelulose (CMC) ? um polissacar?deo derivado da celulose, que se destaca por ser sol?vel em ?gua, renov?vel, biodegrad?vel, de baixo custo e por apresentar possibilidades de modifica??es em sua estrutura qu?mica. Dentre os derivados de carboximetilcelulose, alguns sistemas t?m sido desenvolvidos para induzir propriedades est?mulos-responsivos e ampliar a aplicabilidade desses materiais multirresponsivos. Embora esses novos materiais sejam atualmente objeto de estudo, a compreens?o de suas propriedades f?sico-qu?micas, tais como viscosidade, solubilidade e tamanho de part?culas em fun??o do pH e temperatura ainda ? muito limitada. Esta tese descreve sistemas de misturas f?sicas e copol?meros ? base de carboximetilcelulose e poli (Nisopropilacrilamida) (PNIPAM) com diferentes composi??es percentuais de alimenta??o reacional (25CMC, 50CMC e 75CMC), em solu??o aquosa. A estrutura qu?mica dos pol?meros foi investigada por infravermelho e an?lise elementar CHN. As misturas f?sicas foram analisadas por reologia e os copol?meros foram analisados por UV-vis?vel, espalhamento de raios-X a baixos ?ngulos (SAXS), espalhamento de luz din?mico (DLS) e potencial zeta. CMC e copol?mero foram avaliados como inibidores de incrusta??o de carbonato de c?lcio (CaCO3) usando os testes de compatibilidade qu?mica e precipita??o din?mica em capilar, assim como a microscopia eletr?nica de varredura (MEV). As misturas f?sicas 50% CMC_50% PNIPAM e 25% CMC_75% PNIPAM em solu??o aquosa, nas concentra??es de 6 e 2 g/L, respectivamente, apresentaram comportamento termoviscosificante dependente da concentra??o de pol?mero e da composi??o. Para os copol?meros, o aumento da quantidade de PNIPAM e da temperatura favoreceu as intera??es pol?mero-pol?mero atrav?s dos grupos hidrof?bicos, resultando no aumento da turbidez das solu??es polim?ricas. O tamanho das part?culas diminuiu com o aumento do teor de PNIPAM na composi??o dos copol?meros em fun??o do pH (3-12), a 25 ?C. Maiores quantidades de CMC resultaram em um efeito mais forte do pH nos tamanhos das part?culas, exibindo um comportamento pH-responsivo. Assim, 25CMC n?o foi afetada pela mudan?a de pH, apresentando comportamento similar a PNIPAM. Al?m disso, a presen?a de aditivos de car?ter ?cido ou b?sico influenciou no tamanho das part?culas, que foram menores na presen?a desses aditivos do que em ?gua destilada. Os resultados de potencial zeta tamb?m sofreram maior varia??o para os pol?meros em ?gua destilada do que na presen?a de ?cidos e bases. A temperatura consoluta inferior (LCST) da PNIPAM determinada por DLS foi concordante com o valor obtido por UV-visible. Os dados de SAXS mostraram para PNIPAM e 50CMC uma transi??o de fase quando a temperatura aumentou de 32 para 34 ?C. Um aumento do car?ter polieletrol?tico foi observado em fun??o do aumento da CMC na composi??o dos copol?meros. A avalia??o das amostras como inibidores de incrusta??o mostrou que a CMC apresenta um melhor desempenho do que o copol?mero. Isto foi atribu?do a maior densidade de cargas presente na CMC. As micrografias do MEV confirmaram mudan?as morfol?gicas dos cristais de CaCO3, indicando o potencial desses pol?meros para inibi??o de incrusta??o

This work describes three alternative processes for producing microfibrillated cellulose (MFC; also referred to as cellulose nanofibrils, CNF) in which bleached pulp fibres are first pretreated and then homogenized using a high-pressure homogenizer. In one process, fibre cell wall delamination was facilitated by a combined enzymatic and mechanical pretreatment. In the two other processes, cell wall delamination was facilitated by pretreatments that introduced anionically charged groups into the fibre wall, by means of either a carboxymethylation reaction or irreversibly attaching carboxymethylcellulose (CMC) to the fibres. All three processes are industrially feasible and enable energy-efficient production of MFC. Using these processes, MFC can be produced with an energy consumption of 500–2300 kWh/tonne. These materials have been characterized in various ways and it has been demonstrated that the produced MFCs are approximately 5–30 nm wide and up to several microns long. The MFCs were also evaluated in a number of applications in paper. The carboxymethylated MFC was used to prepare strong free-standing barrier films and to coat wood-containing papers to improve the surface strength and reduce the linting propensity of the papers. MFC, produced with an enzymatic pretreatment, was also produced at pilot scale and was studied in a pilot-scale paper making trial as a strength agent added at the wet-end for highly filled papers. / <p>QC 20150126</p>

>Magister Scientiae - MSc / Glucose oxidase (GOx) and horseradish peroxidase (HRP) are important enzymes for the development of amperometric enzyme linked immunosensors. The selectivity of each enzyme towards its analyte deepens its importance in determining the sensitivity of the resultant immunosensor. In designing immunosensors that have customized transducer surfaces, the incorporation with FAD and iron based enzymes ensures that electron kinetics remains optimal for electrochemical measurement. Various different immobilization strategies are used to produce response signals directly proportional to the concentration of analyte with minimal interferences. The combination of self-assembled monolayers and supramolecular chemistry affords stability and simplicity in immunosensor design. In this work, two electrochemical strategies for the detection of human chorionic gonadotropin(hCG) is presented. This involves the modification of a gold surface with a thiolated β-cyclodextrin epichlorohydrin polymer (βCDPSH) to form a supramolecular inclusion complex with ferrocene (Fc)-functionalised carboxymethyl cellulose polymer (CMC). Cyclic voltammetry indicated that ferrocene is in close proximity to the electrode surface due to the supramolecular complex formed with βCDPSH. Furthermore, strategy (a) for the detection of hCG used α-antihCG labelled (HRP) as reporter conjugate. Strategy (b) maintained the CMC bifunctionalised with Fc and recognition antibody for hCG hormone. However, the system was functionalised with a HRP enzyme and detection is done by using GOx reporter conjugates for in situ production of hydrogen peroxide. The reduction of H2O2 was used for the amperometric detection of hCG by applying a potential of 200 mV. The sensitivity and limit of detection of both strategies were calculated from calibration plots. For strategy (a) the LOD was found to be 3.7283 ng/mL corresponding to 33.56 mIU/mL and a sensitivity of 0.0914 nA ng-1 mL-1. The corresponding values for strategy (b) are 700 pg/mL (6.3 mIU/mL) and 0.94 nA ng-1 mL-1.