Ds. Flournoy et al., CHANGES IN THE SIZE AND VOLUME OF PORES IN SWEETGUM WOOD DURING SIMULTANEOUS ROT BY PHANEROCHAETE-CHRYSOSPORIUM BURDS, Holzforschung, 47(4), 1993, pp. 297-301
The purpose of this study was to examine changes in cell wall void (po
re) volume and pore size distribution in sweetgum wood during decay by
a white-rot fungus, Phanerochaete chrysosporium Burds. Results of the
study may provide quantitative answers to questions regarding the acc
essibility of degradative proteins to their respective substrates with
in the cell wall. Sweetgum (Liquidambar styraeiflua L.) wood blocks we
re decayed by Phanerochaete chrysosporium Burds. in soil-block culture
s. Lignin, cellulose and hemicellulose were removed at approximately e
qual rates with progression of decay. Decay was terminated at various
weight losses, and the pore volumes available to probes of various mol
ecular weight and diameter were determined by the solute exclusion tec
hnique. The cell wall void volume in sound sweetgum wood was 0.35 ml .
g-1 and the maximum pore diameter, 2 nm (20 angstrom). In white-rot d
ecayed wood, cell wall void volume increased to 0.6 ml . g-1 at 40% we
ight loss, and maximum pore diameter increased to more than 5 nm (50 a
ngstrom). Most of the cell wall void volume increase resulted from the
creation of pores of 2 to 5 nm (20 to 50 angstrom) diameter. Assuming
a model in which the cell wall is built of microfibrils laterally ass
ociated to form lamellae, we conclude that ligninolytic enzymes are ex
pected to penetrate only a small fraction of new cell wall void volume
, even after extensive decay, whereas small enzymes of 2 to 3 nm (20 t
o 30 angstrom) may gain access to considerable new cell void volume.