Chemical mediated depolymerization of cotton cellulose for the understanding of non-enzymatic fungal decay
A C Steenkjær Hastrup, B Jensen, F Green III
Small, low molecular weight non-enzymatic compounds have been linked to the early stages of brown rot decay as the enzymes involved with holocellulose degradation are found to be too large to penetrate the S3 layer of intact wood cells. The most pronounced of these which were analyzed in this study are hydrogen peroxide, iron, and oxalic. The compounds related to the Fenton reaction: the combination of hydrogen peroxide and iron caused marked lowering of the degree of polymerization in the cotton cellulose after treatment. This was the case for both iron ions; Fe3+ and Fe2+. A 10mM solution of oxalic acid also showed significant depolymerizing effect on cotton cellulose, whereas diluting the oxalic acid with sodium oxalate to obtain a pH gradient, showed that this decreased the effect reducing of oxalic acid. In addition an organic iron chelator, EDTA, was tested but was found to inhibit depolymerization when in solution with chemicals related to Fenton chemistry. Manganese was tested to see if other metals than iron could generate an significant impact on the degree of polymerization of cotton cellulose and the metal showed good depolymerizing properties as a substitute for iron. We conclude that low molecular weight metabolites are capable of effectively depolymerizing cellulose during incipient decay by brown-rot fungi.