No description available.

This thesis presents two new concepts for separation of micro particles using dielectrophoresis, demonstrated by calculated examples, as well as a new method for obtaining dielectric data on living cells. The thesis is based on four papers. Paper I describes how the trapping efficiency of micro particles may be significantly increased when superpositioned electric fields are employed in a high conductivity medium. Avoiding low conductivity media is important when working with living cells. Calculations were performed to predict trajectories of Escherichia coli bacteria in the system with superpositioned electric fields, and a model was developed which employed two arrays of interdigitated electrodes in a micro channel. Paper II proposes a new concept for separation of micro particles, based on repetitive dielectrophoretic trapping and release in a flow system. Calculations show that the resolution increases as a direct function of the number of trap and release steps, and that a difference in size will have a larger influence on the separation than a difference in dielectrophoretic properties. Polystyrene beads in deionized water were used as a model, and calculations were performed to predict the particle behavior and the separation efficiency. It should be possible to separate particles with a size difference of 0.2 % by performing 200 trap-and-release steps. The enhanced separation power of multi step dielectrophoresis could have significant applications, not only for fractionation of particles with small differences in size, but also for measuring changes in surface conductivity. Paper III presents a new calculation method for predicting dielectrophoretic motion of micro particles. The method is based on a soft sphere method often used in molecular dynamics. Results from the calculations are in good agreement with theoretical predictions as well as initial experimental results, showing that the method provides good efficiency and accuracy. Paper IV describes a new method for measurements of conductivity of living bacteria. To obtain reliable conductivity values, it is important to handle the cells as gently as possible during the measurement process. A standard conductivity meter was used in combination with cross-flow filtration. In this way, repeated centrifugation and resuspension is avoided which otherwise may cause damage to the bacteria. The conductivity of Bacillus subtilis was determined to be 7000 μS/cm by means of the cross-flow filtration method, and the values differ from earlier published values by almost an order of a magnitude. In addition to the work presented in the papers, some experimental dielectrophoresis work in chip-based systems was performed. The behavior of Escherichia coli and polystyrene beads at different voltages and frequencies were studied. Separation of beads with different sizes was achieved on an array of interdigitated electrodes. Using electrodes with a pointed shape, alignment in different directions, pearl-chain formation, rotation, and other dielectrophoretic motion of E. coli were observed. / QC 20101108

A very important trend for studying biomolecules is computational chemistry. In particular, nowadays it is possible to use theoretical methods to figure out the catalytic mechanism of enzyme reactions. Quantum chemistry has become a powerful tool to achieve a description of biological processes in enzymes active sites and to model reaction mechanisms. The present thesis uses Density Functional Theory (DFT) to investigate catalytic mechanism of methyltransferase enzymes. Two enzymes were studied – Glycine N-MethylTransferase (GNMT) and Guanidinoacetate Methyltransferase (GAMT). Different models of the enzyme active sites, consisting of 20 to 100 atoms, are employed. The computed energetics are compared and are used to judge the feasibility of the reaction mechanisms under investigation. For the GNMT enzyme, the methyl transfer reaction was found to follow an SN2 reaction mechanism. The calculations demonstrate that the mechanism is thermodynamically reasonable. Based on the calculations it was concluded that hydrogen bonds to the amino group of the glycine substrate lower the reaction barrier, while hydrogen bonds to carboxylate group raise the barrier. In the GAMT enzyme the methyl transfer reaction was found to follow a concerted asynchronous mechanism which includes transfer of a methyl group accompanied by a proton transfer taking place simultaneously in the same kinetic step. The calculated barrier agrees well with the experimental rate constant. i / QC 20101124

No description available.

No description available.

Sammanfattning Arbete med kemikalier innebär risk för att människor eller miljö utsätts för skadliga ämnen. Arbetsgivare har ansvar för att arbetstagare inte exponeras för farliga kemikalier i sådan nivå att hälsoproblem uppstår. För att uppnå detta krävs att arbetsplatser arbetar aktivt med förebyggande arbetsmiljöarbete. Denna magisteruppsats syftar till att se vilka hinder och möjligheter som kan finnas vid arbete med kemiska arbetsmiljörisker vid universitetslaboratorium. Analyser gjordes som bygger på material insamlat genom intervjuer och besök både på rutin- och forskningslaboratorier vid två sektioner inom samma institution vid Sveriges lantbruksuniversitet (SLU). Resultaten av intervjuerna och studiebesöken visar att sektionerna har ett kemikaliesäkerhetsarbete som ger en arbetsplats som är förhållandevis säker att arbeta på. Engagerade medarbetare och chef bidrog till att rutiner fanns för säkert arbetet på de flesta av de undersökta laboratorierna. En del brister kunde dock ses men de varierade mellan de olika laboratorierna. Kunskap om lagstiftningen kring riskbedömning var bristfällig vilket ledde till att dokumenterade riskbedömningar saknades. Förteckning över alla kemikalier fanns inte tillgänglig för all personal och dokumenterad utredning av cancerogena, mutagena och reproduktionsstörande produkter i verksamheten saknades. Förvaring av lösningsmedel skedde på ett laboratorium i oventilerade skåp trots att bra förvaringsmöjligheter fanns tillgängliga. Vissa svagheter fanns i märkningsrutinerna eftersom riskerna med innehållen i kärlen inte alltid tydligt framgick. Arbete med att byta ut farliga kemikalier mot mindre farliga, så kallad substitution, gjordes inte i full utsträckning. De flesta av bristerna tycks bero på att sektionerna inte är fullt medvetna om vilka risker de utsätts för och inte heller har full kontroll över vilka lagar och regler som finns för att följa lagstiftningens intentioner. I vissa fall beror bristerna på att det bedöms som orimligt att hinna eller ha råd med åtgärder. Insatser som skulle kunna hjälpa till att förbättra säkerhetsarbetet kring kemikalier är att från den centrala organisationen ge information och utbildning till personal på laboratorier om vad lagstiftningen kräver. En förutsättning för att lyckas i kemikaliesäkerhetsarbetet är att arbetet drivs av en engagerad chef med engagerade medarbetare.

No description available.

No description available.

Managing and reducing food waste has increasingly become a global problem in later years, including food waste in the form of fruit pulp from the juice and beverage production industries. Another current urgent issue is the need for a replacement of fossil fuel-based plastics with more sustainable biopolymers. Research has shown that it is possible for a cultivation of microorganisms to engage in the production of biocomposites, while grown on mediums containing fruit waste. In this study fungal biomass grown on apple pomace was observed, as well as the mechanical properties of the obtained biomass, with and without additions of apple pomace, in the form of films. For the cultivations the strain of filamentous fungi Rhizopus Delemar was used. Different types of pre-treatments to the apple pomace were performed such as enzymatic hydrolysis, heat treatment and storing it at room temperature, before filtering and using the apple pomace extract as a cultivation medium. For the enzymatic pre-treatment the enzymes experimented with were pectinase and hemicellulase. The greatest amount of soluble solid concentration in the extracted apple pomace liquid reached was 4.44%, and highest yield of the apple pomace attained was 0.67 g dry substrate/ g dry apple pomace. For the cultivation, the highest obtained concentration of the fungi was 3.91 g/L and the highest yield of the biomass was 0.10 g dry biomass/ g dry substrate. The different types of films produced were also partially treated with glycerol in order to determine whether this treatment was beneficial for the properties of the material. The films showed tensile strength ranging from 1.79 ± 0.06 to 10.37 ± 3.11 MPa, elongation between 0.65 ± 0.08 and 9.86 ± 0.42% and E-modulus at 0.12 ± 0.02 to 0.96 ± 0.07 GPa. Although growing fungi in apple pomace was achievable, the types of biocomposite materials made were discovered to be relatively brittle. However, certain traits similar to those of leather and paper were displayed.

The  supply  of  energy  and  the  protection  of  the  environment  have  been  two  of  the most  important problems  to have affected mankind  in  recent decades.The waste management  is become a very  crucial environmental problem in the world, due to the ever increasing amount of waste material, domiciliary and industrial, generated. The main strategies for the waste management are the protection of the environment and used to produce energy.  Lignin, the second most abundant component besides cellulose in biomass. In this study,  lignosulfonate, is used as fuel in the solid oxide fuel cell to produce a power and heat, which is a byproducts from the wood pulp using sulfite pulping. To enhance the performance and conductivity of the biomass based fuel cell, the lignin was treated with hydroxides (Li/K) and chlorides (Fe2Cl3) at different temperature 200 -500 °C.  The maximum obtained power density was about 20 mW/cm2. And the calculated electrical efficiency of the cell was about 30%.   Also,  this kind of biomass fuel was used  in single component fuel cell and  results were compared with three components fuel cell.  The phase analysis, microstructure and conductivity of lignin was analysed by XRD, SEM and AC impedance technique.  It has been concluded that a sulfonated  lignin from waste of the paper industry can be used  as a energy sources with fuel cell operation.