The Chelator Mediated Fenton System in the Brown Rot Fungi: Details of the Mechanism, and Reasons Why it has Been Ineffective as a Biomimetic Treatment in some Biomass Applications – a Review
B S Goodell, M Nakamura, J Jellison
The chelator-mediated Fenton (CMF) reaction requires the action of two types of chelating compounds. The first chelator, oxalate, solubilizes and then sequesters iron, and the second chelator reduces iron. Iron reduction must be controlled near the fungal hyphae to prevent damaging Fenton chemistry from occurring in that location. Similarly, iron reduction must be promoted within the wood/plant cell wall to promote Fenton chemistry in the proximity of the target lignocellulose. The mechanism for that control is reviewed in this paper. Both neat Fenton and the CMF have been examined by researchers seeking to exploit this relatively simple mechanism for biomass conversion and lignocellulose pretreatment systems. This paper reviews why some of that research has not produced useful depolymerization reactions and why excess amounts of reagents have been required. The application of Fenton treatments requires that the reactive oxygen species produced in the reaction be generated within a nanometer of the target substrate (lignocellulose), and for this to occur in biomass treatments using Fenton or CMF systems, iron must first be allowed to bind to the substrate to allow the reactions to proceed within nanoscale proximity to lignocellulose. Further, excess iron in solution and in interstitial space must be removed as this “free” iron will react preferentially with chelators and peroxide preventing appropriate targeted action on lignocellulose.
Keywords: Fenton chemistry, chemical mechanisms, chelators, brown rot, fungi, renewable energy, biomass, pretreatment, iron, lignocellulose