Contributions to research on white-rot fungi, lignin-degrading enzymes, and their industrial and environmental applications

Abstract

White-rot fungi (WRF), the most frequent wood-rotting organisms, are so far unique in their ability to completely degrade all components of our principal renewable resource, lignocellulose. They produce an impressive array of enzymes (cellulases, hemicellulases, pectinases and ligninases) with potential in a wide range of biotechnological applications. WRF and their ligninolytic enzymes (such as laccase and Mn-peroxidase) are able to degrade many pollutants. In pulp and paper manufacturing they are applied in biopulping, biobleaching and effluent treatment. Recently, there has been a growing interest in studying the ligninolytic enzymes of a wider array of WRF, with the expectation of finding better lignin-degrading systems for use in various biotechnological applications. To be able to use the white-rotters in these processes it is necessary to learn how their enzymes are secreted, how they operate and under what conditions they are active. Our current research is focused on these subjects and in the screening of new isolates for their ability to degrade xenobiotics, in the search of more efficient strains. Reducing the cost for enzyme production is still needed in order to develop enzymatic treatment processes for different industrial and environmental applications, competitive with other treatment technologies. At present, one of the objectives of our work is reducing this cost by means of process optimization using statistical experimental designs, and the use of cheaper growth substrates such as agricultural and food wastes. We identified new strains of Trametes versicolor, Trametes villosa, Stereum hirsutum and Fomes sclerodermeus which demonstrated an outstanding ability in dye degradation. Trametes trogii BAFC 463 almost completely removed several dyes as well as high priority pollutants such as polycyclic aromatic hydrocarbons and polychlorinated biphenyls. Pycnoporus sanguineus BAFC 2126 proved to be a potential candidate for use in softwoods biopulping processes. Efficient bleaching of loblolly pine kraft pulp could be achieved in a chlorine-free sequence, with culture supernatants from T. trogii, followed by a peroxide stage under mild conditions. Its high potential purified laccase, was recently applied as biocatalyst for oxygen electro-reduction in biofuel cells. With our results we wish to contribute to expand the knowledge on this important group of fungi and their biotechnological applications.