Cellulose Degradation Mediated by Chelators Isolated from Gloephyllum trabeum: Mechanisms of Wood Degradation by Brown- Rot Fungi
- Xu, Gang
Graduate School, University of Maine
Iron, hydrogen peroxide, biochelators and oxalate are believed to play important roles in cellulose degradation by brown-rot fungi. The effects of these compounds on α-cellulose degradation were investigated in this study by determining the changes of molecular weight distribution of cellulose after degradation using gel permeation chromatograph (GPC) analysis. In addition, cellulose-iron affinity was studied. this study shows the chelators isolated from brown-rot fungus Gloeophylum trabeum (Gt chelator) accelerated cellulose degradation in the presence of Fe III (0.5mM) and H2O2 (10mM and 80mM). Below a certain concentration level (200 µM for 10mM H2O2, 500µ for 80 mM H2O2), cellulose degradation increased with increasing iron concentration, while above this certain concentration level, increasing iron concentration, while above this certain concentration level, increasing iron concentration inhibited cellulose degradation. Hydrogen peroxide was a decisive reagent for cellulose degradation. The amount of H2O2 determined the extent of degradation. Oxalate, within the concentration levels used in this study, diminished cellulose degradation in the presence of Fe III, H2O2 and Gt chelator.
Cellulose-iron affinity studies were conducted at three pH levels (3.6, 3.8, 4.1), and the binding constants of cellulose-Fe II, cellulose-Fe II and cellulose-Fe III in the presence of GT chelator were calculated. The binding constants for cellulose-FE II in the presence of Gt Chelator were calculated. The binding constants for cellulose0FE II at all three pH levels were much higher than those for cellulose-Fe II and cellulose-Fe II in the presence of FT chelator were calculated. The binding constants for cellulose-Fe II at all three pH levels were much higher than those for cellulose-Fe II, and the binding constants for cellulose-Fe II in the presence of Gt chelator were very close to those for cellulose-Fe II, which probably occurred as a result of Fe II reduction to Fe II by Gt chelator.
A mechanism for cellulose degradation by brown-rot fungi and G. trabeum in particular is proposed based on the above data.
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