Ana P. V. Egas

Bio: Ana P. V. Egas is an academic researcher from University of Coimbra. The author has contributed to research in topics: Kraft process & Viscosity. The author has an hindex of 7, co-authored 11 publications receiving 129 citations.

Evolution of Methylglucuronic and Hexenuronic Acid Contents of Eucalyptus globulus Pulp during Kraft Delignification

Abstract: The evolution of 4-O-methylglucuronic (GlcA) and hexenuronic (HexA) acids contents during kraft pulping of Eucalyptus globulus was investigated. Different operating conditions were considered in the range of 80−165 °C for temperature, 10−45 g of Na2O/100 g of oven-dried wood for effective alkali charge, and 15−75% for sulfidity, with a liquid-to-wood ratio of 8 L/kg. The GlcA content was about 5% in the native wood and decreased continuously throughout the cook. Up to 87% of this component was consumed, being dissolved together with the xylan chain or converted to HexA. The latter were detected for temperatures higher than 110 °C. The highest HexA values (∼40 mmol/kg of oven-dried pulp) were observed for delignification degrees close to those of industrial bleachable pulps, and the subsequent decrease in their content was only noticeable for lower lignin amounts. The temperature and the effective alkali charge were confirmed to have a strong influence on the HexA content profiles and on the degradation/di...

Experimental Methodology for Heterogeneous Studies in Pulping of Wood

Abstract: The heterogeneous nature of the kraft pulping of wood is experimentally demonstrated in this paper, and a new methodology for kraft pulping investigation is presented. The strategy proposed here enables the measurement of alkali and of lignin concentrations in the pulping liquor, both inside and outside of the wood chips. With this procedure, it is possible to independently determine, in both entrapped and free liquors, the time histories of the concentrations of alkali and lignin as well as total dissolved solids, which are a direct result of the mass transfer and of the chemical reactions that take place during this heterogeneous process. The influence of the chip thickness and of temperature on the relative rates of these two phenomena is also highlighted. This experimental methodology establishes the foundations for the development of a macroscopic heterogeneous kraft pulping model that can be experimentally validated in pulping conditions, even for modified digester processes.

A review on non-edible oil as a potential feedstock for biodiesel: physicochemical properties and production technologies

Abstract: There is increasing concern regarding alleviating world energy demand by determining an alternative to petroleum-derived fuels due to the rapid depletion of fossil fuels, rapid population growth, and urbanization. Biodiesel can be utilized as an alternative fuel to petroleum-derived diesel for the combustion engine. At present, edible crops are the primary source of biodiesel production. However, the excessive utilization of these edible crops for large-scale biodiesel production might cause food supply depletion and economic imbalance. Moreover, the utilization of edible oil as a biodiesel feedstock increases biodiesel production costs due to the high price of edible oils. A possible solution to overcome the existing limitations of biodiesel production is to utilize non-edible crops oil as a feedstock. The present study was conducted to determine the possibility and challenges of utilizing non-edible oil as a potential feedstock for biodiesel production. Several aspects related to non-edible oil as a biodiesel feedstock such as overview of biodiesel feedstocks, non-edible oil resources, non-edible oil extraction technology, its physicochemical and fatty acid properties, biodiesel production technologies, advantages and limitation of using non-edible oil as a feedstock for biodiesel production have been reviewed in various recent publications. The finding of the present study reveals that there is a huge opportunity to utilize non-edible oil as a feedstock for biodiesel production.

AggFluor: Fluorogenic Toolbox Enables Direct Visualization of the Multi-Step Protein Aggregation Process in Live Cells

Abstract: Aberrantly processed or mutant proteins misfold and assemble into a variety of soluble oligomers and insoluble aggregates, a process that is associated with an increasing number of diseases that are not curable or manageable. Herein, we present a chemical toolbox, AggFluor, that allows for live cell imaging and differentiation of complex aggregated conformations in live cells. Based on the chromophore core of green fluorescent proteins, AggFluor is comprised of a series of molecular rotor fluorophores that span a wide range of viscosity sensitivity. As a result, these compounds exhibit differential turn-on fluorescence when incorporated in either soluble oligomers or insoluble aggregates. This feature allows us to develop, for the first time, a dual-color imaging strategy to distinguish unfolded protein oligomers from insoluble aggregates in live cells. Furthermore, we have demonstrated how small molecule proteostasis regulators can drive formation and disassembly of protein aggregates in both conformational states. In summary, AggFluor is the first set of rationally designed molecular rotor fluorophores that evenly cover a wide range of viscosity sensitivities. This set of fluorescent probes not only change the status quo of current imaging methods to visualize protein aggregation in live cells but also can be generally applied to study other biological processes that involve local viscosity changes with temporal and spatial resolutions.