Study of Basic Wood Decay Mechanisms and Their Biotechnological Applications

The overall objective of this thesis was to gain further understanding of the non-enzymatic mechanisms involved in brown-rot wood decay, especially the role of pH, oxalic acid, and low molecular catecholate compounds on the dissolution and reduction of iron, and the formation of reactive oxygen species. Another focus of this study will be the potential application of a biomimetic free radical generating system inspired from fungi wood decay process, especially the non-enzymatic mechanism. The possible pathways of iron uptake and iron redox cycling in non-enzymatic brown-rot decay were investigated in this study. UV-Vis spectroscopy and HPLC were employed to study the kinetics and pathways of the interaction between iron and model catecholate compounds under different pH and chelator/iron molar ratio conditions. Iron chelation and reduction during early non-enzymatic wood decay processes have been studied in this thesis. The results indicate that the effects of the chelator/iron ratio, the pH, and other reaction parameters on the hydroxyl radical generation in a Fenton type system can be determined using ESR spin-trapping techniques. Data also support the hypothesis that superoxide radicals are involved in chelator-mediated Fenton processes. The mechanisms involved in free radical activation of Thermal Mechanical Pulp fibers were investigated. The activation of TMP fibers was evaluated by ESR measurement of free phenoxy radical generation on solid fibers. The results indicate that low molecular weight chelators can improve Fenton reactions, thus in turn stimulating the free radical activation of TMP fibers. A mediated Fenton system was evaluated for decolorization of several types of dyes. The result shows that the Fenton system mediated by a catecholate-type chelator effectively reduced the color of a diluted solution of synthetic dyes after 90 minutes of treatment at room temperature. The results show that compared to a neat Fenton process, the mediated Fenton decolorization process increased the production, and therefore the effective longevity, of hydroxyl radical species to increase the decolorization efficiency.