Lösligheten av xylaner utvunna från trä undersöktes med Dynamisk Ljusspridning i syfte att observera eventuella förändringar i hydrodynamisk volym och ζ-potential. Xylaner extraherade från bok, björk och gran användes, där alkalisk extraherad bok erhölls kommersiellt och prover från björk och gran extraherades i förhand med subkritiskt vatten och alkalisk extraktion. Proverna analyserades vid koncentrationerna 1 g/L respektive 20 g/L. Förändringar i pH observerades stegvis med titrering av 1 g/L prover och förändringar över tid vid konstant pH observerades upp till en vecka efter upplösning. 20 g/L proverna undersöktes över tid vid bestämda pH enligt samma process för 1 g/L för både filtrerade och ofiltrerade prover. En undersökning av utvalda filter genomfördes där stora variationer observerades mellan det olika arterna men även mellan filtrens porstorlek. Med dynamisk ljusspridning observerades att populationer av högsta molekylvikt avlägsnades, där inverkan var störst för proven med lägst total koncentration och för högre koncentration efter en vecka. SEC visade att även populationer med mindre molekylvikt avlägsnades som medför att aggregering av proven kan ha förekommit, vilket kan ha förhindrat passingering genom filtren. Med några få undantag, samtliga provers hydrodynamiska volym visades vara heterogena, med endast små ökningar vid ökning i koncentration och icke-signifikanta förändringar över tid och med varierande pH. ζ-potentialvärdena visade markanta förändringar och tydliga trender med ändringar i pH och koncentration, där minskande pH och ökande koncentrationer resulterade i minskad stabilitet i lösning. Över tid ökades absolut ζ-potentialen för de prover med högre koncentration för alla pH miljöer. Filtrering av 20 g/L proverna resulterade i högre initial ζ-potential men efter en vecka ökade stabiliteten för de ofiltrerade till något högre slut ζ-potential för ofiltrerade. / The solubility of wood xylans was investigated using Dynamic Light Scattering to calculate number-average size and ζ-potential of samples in aqueous solution. The sources of xylan were a commercial alkaline extracted beech glucuronoxylan as well as pre-prepared samples of birch glucuronoxylan and spruce arabinoxylan, extracted using subcritical water extraction and alkaline extraction. The samples were analysed at concentrations of 1 g/L and 20 g/L, where the lower concentration samples were analysed at varying pH using titration and set pH over the span of hours and finally up to a week after preparation. The higher concentration samples were observed at set pH following the same procedure as the lower concentration for both filtered and unfiltered samples. An analysis of the filtration of 1 g/L samples was conducted by freeze-drying and weighing the samples before and after using 0.2 μm and 1.2 μm filters. These were then compared to unfiltered samples to evaluate the loss of total mass after filtration. The results of this investigation found significant variance between the samples and filters selected. Comparisons of filtered and unfiltered samples consistently showed that the filtration removed higher molecular weight portions of the samples, the most significant differences being observed at lower concentrations and higher concentration after 1 week. SEC analysis showed that not only larger molecular weight fraction but all the observed populations were removed during filtration, indicating that aggregates could be present, inhibiting the smaller molecular weight fractions from passing through. The size measurements showed that the vast majority of samples were heterogeneous in nature and with a slight increase in number-average size with increasing concentration and little change when varying both pH and over time. ζ-potential measurements showed substantial changes in stability when varying pH, coinciding well with predicted pKa values and generally decreased stability at higher concentrations. For higher concentrations lower initial absolute ζ-potential values were observed for both filtered and unfiltered however over time the unfiltered samples showed slightly greater increases for all measured pH values.

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<p>  </p> <p>An optical technique that discriminates microbial organisms using an elastic light scatter (ELS) pattern, known as BActeria Rapid Detection using Optical Technology (BARDOT), has shown excellence in pathogen screening which effectively saves time and cost during the identification. Owing to the successful implementation of the light-scattering technique in microbiology, a series of studies on the light scatter pattern have been conducted to improve the technology. As an extended study of the multispectral application in BARDOT, a hyperspectral elastic light-scatter phenotyping instrument (HESPI) was developed to increase the ability to discriminate and detect foodborne pathogens. The newly designed instrument integrated a supercontinuum (SC) laser into the traditional BARDOT system to provide a broad spectrum of the light source. An acousto-optic tunable filter (AOTF) was utilized to select the wavelength of interest, allowing multiple spectral patterns in a single measurement. Owing to the filtering mechanism of AOTF, the wavelength of the laser was shifted rapidly so the overall acquisition time of 80 hyperspectral patterns was less than30 seconds. A pair of optical lenses were used to compensate for the beam spot movement caused by the wavelength-dependent separation angle at the exit of AOTF. To capture the transmitted scattering patterns, a complementary metal-oxide-semiconductor (CMOS) sensor was placed under the bacteria sample plate.</p> <p>For a comprehensive understanding of the ELS patterns, at first, the diverse nature of bacterial colony morphology was explored. Using the optical scatter model based on the scalar diffraction theory, the forward light-scatter patterns were simulated with respect to various colony shapes. The numerical predictions were then compared to the scattering patterns that were experimentally obtained from the colonies with various elevation profiles. The experimental verification proved a strong correlation between the colony morphology and the ELS pattern, as an excellent agreement between the simulation and the experiment observed. Second, the wavelength-dependent characteristics of the ELS patterns were investigated. Based on the theoretical and experimental interrogation, the wavelength of the incident laser beam affected the shape of ELS patterns by the overall size, the number of diffraction rings, and the gap distance between the rings. </p> <p>The performance of HESPI was validated by differentiating green leafy microflora using the hyperspectral ELS patterns. A group of bacteria that were poorly classified with the traditional single-wavelength method was selected to prove the improvement of the classification by the hyperspectral application. HESPI was utilized to measure the hyperspectral ELS patterns of their colonies, and for the classification, the descriptive features were extracted from the patterns at 70 selected wavelengths within the 473 – 709 nm region. A classification model was constructed for every wavelength, and the classification accuracy of the individual model ranged from 88.7% to 93.2%. The classification result also showed that colonies of varied species produced distinctive scatter features at a particular spectral band. When employing the entire wavelengths for the classification, the more number of wavelengths consequently led to an increase in the number of scatter-pattern features. This could cause the classifier's overfitting and negatively affect the classification. Therefore, the presented work incorporated various feature reduction and selection procedures to enhance the robustness and ultimately lessen the complexity of data collection. A classification model with feature reduction improved the overall classification rate to 95.9% after selecting meaningful predictors.</p>