No description available.

Under cellulolytic conditions, the white-rot fungus Trametes versicolor produces cellobiose dehydrogenase (CDH), an enzyme with a number of biochemical properties that are potentially relevant to the degradation of lignin and cellulose. To clarify its biochemical properties, CDH was purified from cultures of T. versicolor. Two isoforms of CDH were found: a 97 kDa isoform with both heme and flavin cofactors, and an 81 kDa isoform with a flavin cofactor. Both isoforms of CDH were found to be quite non-specific in their reductive half reactions. The flavin enzyme catalyzed many of the same reactions as the heme/flavin enzyme, but less efficiently. The flavin isoform reduced Fe(III) and Cu(II) only at concentrations well above those found physiologically. Thus the heme/flavin enzyme, but not the flavin enzyme, could be involved in promoting and sustaining the generation of hydroxyl radicals (·OH) by Fenton's chemistry. / To characterize further the structural features of CDH, a genomic clone was isolated and sequenced. CDH was found to consist of 748 amino acids, without its predicted 19 amino acid signal peptide. Consistent with the domain structure of other CDHs, T. versicolor CDH appeared to be divided into an amino terminal heme domain and a carboxy terminal flavin domain, connected by a hydroxyamino acid-rich linker. Within the flavin domain, a putative cellulose-binding domain (CBD) was found by alignment to the hypothesized CBD of P. chrysosporium CDH. The CBD of CDH appeared to be structurally unrelated to other CBDs which have been reported. / A cDNA clone encoding T. versicolor CDH was isolated by RT-PCR. Using this clone, three vectors for the heterologous expression in Aspergillus oryzae of CDH were prepared. These vectors were built by performing in-frame fusions of the cDNA to control sequences from the highly expressed A. oryzae amylase gene. These vectors were transformed into A. oryzae and one strain was isolated which contained the expression construct DNA. / A rapid method for cloning cdh-like genes was developed. Using short stretches of amino acids completely conserved within T. versicolor and P. chrysosporium CDH, PCR primers were designed to amplify a homologous gene from other fungi. The primers were tested using genomic DNA of Pycnoporus cinnabarinus. A 1.8-kb fragment of P. cinnabarinus cdh was thereby amplified and cloned, and its sequence was determined. The three CDHs displayed very high homology at the amino acid level. / Finally, to probe the role of CDH in lignocellulose degradation by T. versicolor, a "knockout" vector was constructed consisting of a phleomycin-resistance cassette inserted into the protein coding sequence of cloned T. versicolor cdh. T. versicolor was transformed with the knockout vector and the transformants were analyzed for their CDH-producing phenotype. Three isolates were found that produced no detectable CDH. Biobleaching and delignification by the CDH(-) strains appeared to be unaffected, suggesting that CDH does not play an important role in these processes.

Syftet med arbetet var att undersöka hur olika reaktionsbetingelser skulle påverka syrgasdelignifieringen av en sur sulfitmassa. De betingelser som undersöktes var utbyte, slut-pH, viskositet och kappatal. Massan som användes kom från Nordic Paper Seffle och alkalit som användes var magnesiumoxid.  Syrgasdelignifiering av massan gjordes  i autoklaver i ett PEG bad där tid, temperatur och alkalisatser varierades. Resultaten visar att alla utbyten låg mellan 90-97% och att även de mest aggressiva betingelserna bara gav en viskositets reduktion på 260 enheter, motsvarande 19% av den totala viskositeten. Slut-pH för syrgasavluten hamnade mellan 6,5-9,4 beroende på alkalimängd och temperatur under delignifieringen. Slut-pH minskade när mängden alkali hölls konstant men temperaturen varierades mellan 110-140°C. Kappatalet för massan kunde effektivt reduceras från ett startvärde på 23,4 till ett slutvärde på under 5 med en temperatur på 140°C, alkalisats på 10 kg/ODT och en tid på två timmar utan större förluster av vare sig viskositet eller utbyte. En ovanligt resultat som upptäcktes under arbetet var att delignifieringen tappade i effektivitet med ökad alkalimängd och detta samband gällde vid alla betingelser. En teori om detta kan vara att jonstyrkan i lösningen gör att fibrerna i massan drar ihop sig och att syrgasen får svårare att reagera med ligninet. / The purpose of the study was to investigate how different reaction conditions would affect oxygendelignification of an acid sulfite pulp. The conditions being explored were yield, final-pH, viscosity and kappa number. The pulp used in the testing was collected from Nordic Paper Seffle and the active alkali during the delignification was magnesium oxide. The oxygendelignification of the pulp was done with autoclaves suspended in a PEG bath, where they were allowed to rotate, and time, temperature and alkali amount  was varied throughout the testing. Results show that the yield for all pulp samples were between 90-97% for all conditions used in this project while viscosity of the pulps were only decreased by about 260 units for the most severe of conditions. This accounts for a viscosity loss of 19%. Final-pH varied between 6,5-9,4 depedning on temperature and alkali amount chosen. Final-pH levels dropped when the alkali was kept constant but temperature was varied from 110-140°C. The pulps kappa number could effetively be lowered from its starting value of 23,4 to a final value of under 5 when an alkali amount of 10 kg/ODT and a temperature of 140°C was used during 2 hours. This lead to no substantial losses of either viscosity or yield. A strange result that the project also highlighted was that the delignification lost in efficiency when more alkali was added in at a set temperature. This phenomenom was found at all conditions investigated throughout the project. A theory about this is that it might be the increased ionic strength from the magnesium cations in the solution making the fibers shrink and by that lessening the reaction area of the fibres for the oxygen, which will then have a harder time reacting with the lignin.

This thesis will show the possibility for the development and use of an on-line model for application to continuous digesters for pulp production. The model is developed by using a program called Dymola (Dynamic Modeling Laboratory). What makes the Dymola software so well suited is that the program solves equations simultaneously. The model is a further development from the Purdue model [Bhartiya et al, 2003]. The main difference between this model and the Purdue model however, is the dynamics in the model. The dynamics are very important when you use the model for control purposes because the cooking process has long dead and retention times. The main purpose of this model is to use it for the advanced control of continuous digesters as well as giving the operators a better understanding of what happens in the cooking process when changes are made. The model will also be used for diagnostic purposes. Advanced control in this case is Model Predicted Control (MPC). The MPC will control the quality of the pulp “kappa” number and the chemical consumption during digestion. This thesis describes the model and results are shown for applications of on-line diagnosis in three pulp mills in South Africa. Real time process data from the pulp mills is fed into the model and a simulation is performed. Thereafter, the results from the simulation are compared to the actual measured data for a number of key variables. By comparing the simulation results to the real process data and following the trends of the deviations between the two, different types of faults and upsets can be detected in both the process and sensors. / KKS project:Use of physical models combined with statistical models for improved digester control

This work presents a novel means of producing thin-film light-emitting devices, functioning according to the principle of electroluminescence, using an inkjet printing technique. This study represents the first report of a light-emitting device deposited completely by inkjet printing. An electroluminescent species, doped zinc sulfide, was incorporated into a polymeric matrix and deposited by piezoelectric inkjet printing. The layer was printed over other printed layers including electrodes composed of the conductive polymer poly(3,4-ethylenedioxythiophene), doped with poly(styrenesulfonate) (PEDOT:PSS) and single-walled carbon nanotubes, and in certain device structures, an insulating species, barium titanate, in an insulating polymer binder. The materials used were all suitable for deposition and curing at low to moderate (<150°C) temperatures and atmospheric pressure, allowing for the use of polymers or paper as supportive substrates for the devices, and greatly facilitating the fabrication process. The deposition of a completely inkjet-printed light-emitting device has hitherto been unreported. When ZnS has been used as the emitter, solution-processed layers have been prepared by spin-coating, and never by inkjet printing. Furthermore, the utilization of the low-temperature-processed PEDOT:PSS/nanotube composite for both electrodes has not yet been reported. Device performance was compromised compared to conventionally prepared devices. This was partially due to the relatively high roughness of the printed films. It was also caused by energy level misalignment due to quantization (bandgap widening) of the small (<10 nm) nanoparticles, and the use of high work function cathode materials (Al and PEDOT:PSS). Regardless of their reduced performance, inkjet printing as a deposition technique for these devices presents unique advantages, the most notable of which are rapidity of fabrication and patterning, substrate flexibility, avoidance of material wastage by using drop-on-demand technology, and the need for only one main unit operation to produce an entire device.

Physical property data was used to test two hypotheses pertaining to the impact of a chemical pre-treatment on the qualities of low consistency refined pulp. The first objective was to determine whether the addition of a chemical treatment would effectively accelerate the refining process when compared to a regular pulp. This involved the measurement of the physical property data and how it changed with increased refining energy. The second objective was to determine how the chemical treatment affected fibre development during refining, and whether its implementation could result in enhancement of inter-fibre bondability. Theoretical models for the physical properties of paper were used to study the fibre-to-fibre bonding properties of the tested paper samples. Additionally, SEM images were obtained to study the deferences in morphology of the tested pulp samples.

This work presents a novel means of producing thin-film light-emitting devices, functioning according to the principle of electroluminescence, using an inkjet printing technique. This study represents the first report of a light-emitting device deposited completely by inkjet printing. An electroluminescent species, doped zinc sulfide, was incorporated into a polymeric matrix and deposited by piezoelectric inkjet printing. The layer was printed over other printed layers including electrodes composed of the conductive polymer poly(3,4-ethylenedioxythiophene), doped with poly(styrenesulfonate) (PEDOT:PSS) and single-walled carbon nanotubes, and in certain device structures, an insulating species, barium titanate, in an insulating polymer binder. The materials used were all suitable for deposition and curing at low to moderate (<150°C) temperatures and atmospheric pressure, allowing for the use of polymers or paper as supportive substrates for the devices, and greatly facilitating the fabrication process. The deposition of a completely inkjet-printed light-emitting device has hitherto been unreported. When ZnS has been used as the emitter, solution-processed layers have been prepared by spin-coating, and never by inkjet printing. Furthermore, the utilization of the low-temperature-processed PEDOT:PSS/nanotube composite for both electrodes has not yet been reported. Device performance was compromised compared to conventionally prepared devices. This was partially due to the relatively high roughness of the printed films. It was also caused by energy level misalignment due to quantization (bandgap widening) of the small (<10 nm) nanoparticles, and the use of high work function cathode materials (Al and PEDOT:PSS). Regardless of their reduced performance, inkjet printing as a deposition technique for these devices presents unique advantages, the most notable of which are rapidity of fabrication and patterning, substrate flexibility, avoidance of material wastage by using drop-on-demand technology, and the need for only one main unit operation to produce an entire device.

Physical property data was used to test two hypotheses pertaining to the impact of a chemical pre-treatment on the qualities of low consistency refined pulp. The first objective was to determine whether the addition of a chemical treatment would effectively accelerate the refining process when compared to a regular pulp. This involved the measurement of the physical property data and how it changed with increased refining energy. The second objective was to determine how the chemical treatment affected fibre development during refining, and whether its implementation could result in enhancement of inter-fibre bondability. Theoretical models for the physical properties of paper were used to study the fibre-to-fibre bonding properties of the tested paper samples. Additionally, SEM images were obtained to study the deferences in morphology of the tested pulp samples.

No description available.

Hornification is the term used to describe the irreversible changes that occur in cellulose fibers due to recycling. While the effects of hornification have been documented, there are several conflicting hypotheses that attempt to explain the causes. In this research, AFM surface adhesion measurements made on virgin and recycled bleached kraft pulp show that recycling increases the apparent hydrophilicity of the fiber surface. Yet, the water retention values and tensile strength decrease as expected, which is consistent with internal cross-linking of the bonding sites and a reduction in hydrophilicity. Recycling does not affect the amount of monolayer water bound to the fiber surface indicating that the pore water is reduced but not the water bound to fiber surfaces. It is proposed that the contact area between the AFM tip and the fiber is greater for recycled material than for virgin. Image analysis of the fiber surface supports this conclusion, revealing a decrease in the surface roughness. The irregularity of fiber surfaces is apparent in AFM images at all but the smallest scales, with macroscopic fiber features dominating the roughness analyses of images larger than 2500 square nanometers. Hence, in this instance, the surface adhesion values are more a measure of the topography of the surface than of its chemistry. An application to newsprint is illustrated, revealing the limitations of AFM analysis of samples with a high degree of variability.