Investigation of the effect of metal ions and mediators on the delignification selectivity during pretreatment of poplar wood by Phanerochaete chrysosporium.

Microbial pretreatment of lignocellulosic biomass is performed to delignify the substrate for further use of the carbohydrates present. Typical applications of the pretreated substrate include its conversion to chemicals by subsequent hydrolysis and fermentation, or biopulping for use in the paper industry. In contrast to the traditional technologies at high temperature and high usage of solvents, microbial pretreatment is an environmentally friendly technology. The mold Phanerochaete chrysosporium is a good candidate for lignin degradation because of its fast growth and high optimal growth temperature. For delignification purposes, the mold excretes extracellular peroxidases, i.e. manganese peroxidase and lignin peroxidase, that catalyse the oxidation and depolymerisation of lignin. However, the major disadvantage is the non-selective degradation of the lignin over the present carbohydrates. Supplements, such as metal ions and aromatic compounds, can have an activating or inhibiting action on the delignification or hydrolysis process. Moreover, recent research showed that some metal ions and aromatic compounds can act as intermediates in the oxidation of non-phenolic compounds, such as carbohydrates. Delignification of lignocellulose and hydrolysis as well as oxidation of carbohydrates will determine the efficiency of the pretreatment, dependent on the desired application. Therefore, in this research, the influence of supplements on the different possible actors in the process, i.e. substrate, microorganism and enzymes, will be investigated. Better insights in the pretreatment will help to determine which combination and concentration of supplements will improve the application potential of the pretreated wood. Additionally, a improved method for easy determination of the growth rate and delignification rate based on FTIR will be developed. Finally, a mathematical model to describe the evolution of delignification process will be proposed.

Keywords:PEROXIDASE, SOLID STATE FERMENTATION, LIGNOCELLULOSE, FUNGI

Disciplines:Biochemistry and metabolism, Microbiology, Fermentation, Industrial microbiology