Enhancing Our Understanding of Brown Rot Mechanisms through Catalytic Pretreatment and Cellulase Cocktail
S Tabor, L Orjuela, D Contreras, G Alfredsen, J Jellison, S Renneckar, B Goodell
A catalytic mechanism, described as the “chelator-mediated Fenton” (CMF) mechanism, is proposed to mimic the non-enzymatic action of brown rot fungi. A CMF treatment was used together with an enzymatic cocktail to study how wood was deconstructed and solubilized. This was done in-part to determine if the treatment mimicked the action of brown rot fungi, but also to explore improved treatment processes for bioprocessing of woody biomass. Our data suggest that the CMF mechanism is highly efficient in overcoming the lignin recalcitrance barrier to solubilize wood. Multiple pulses (up to 4 pulses) of CMF treatment were able to solubilize a majority of both the lignin and cellulose of wood at room temperature, using a hydrogen peroxide concentration of only 1%. Using a single pulse of the CMF system as a pretreatment allowed more wood residue to be retained, and enzymatic action on this pretreated wood was enhanced compared to control wood. In separate experiments, significantly greater solubilization of both sugars and lignin occurred when a single-pulse CMF pretreatment was used prior to enzymatic action than by enzymatic action alone on unmodified wood. This work suggests a key reason why the brown rot fungi have abandoned many of their extracellular enzymes to produce only a select suite of cellulases, which the fungus employs after prior modification of the cell wall using a CMF mechanism. This research further suggests that the CMF mechanism may have potential to be adapted for bioprocessing of woody biomass to produce sustainable fuels and bioproducts in the future.