P. Ander, EFFECTS OF CELLOBIOSE DEHYDROGENASE ON GUAIACYL AND GUAIACYL SYRINGYLLIGNINS IN THE PRESENCE OF IRON AND HYDROGEN-PEROXIDE/, Holzforschung, 50(5), 1996, pp. 413-419
Fe(III) reduction by cellobiose dehydrogenase (CDW) in the presence of
hydrogen peroxide and guaiacyl or syringyl lignins was investigated.
These two wood lignins behaved differently and reduction of Fe(III) by
CDH was markedly decreased by the presence of synthetic lignin of the
guaiacyl type or by milled wood lignin from spruce. with milled wood
lignin from birch (guaiacyl/syringyl lignin) no decrease but rather a
weak increase in Fe(III) reduction was obtained. Since it has been pro
posed that Fe(II) plus hydrogen peroxide can form hydroxyl radicals an
d/or iron(per)oxo complexes able to degrade lignin, it was investigate
d whether lignin-related phenols and quinones affected Fe(III) reducti
on. It was found I:hat vanillic and syringic acids, vanillin and syrin
galdehyde al! increased Fe(III) reduction by CDH + cellobiose in the p
resence of hydrogen peroxide. When Fe(III) and methoxyquinone were pre
sent together, they were simultaneously reduced at a common wavelength
. This reducing activity was mainly additive depending on the reductio
n of the separate components. Since dimethoxyquinone was reduced more
slowly it had little influence on CDH-catalyzed Fe(III) reduction. It
is proposed that hydroxyl radicals and/or iron(per)oxo complexes prefe
rentially attack hardwood lignin (guaiacyl/syringyl) thereby releasing
phenols and quinones during consumption of hydrogen peroxide which ma
y otherwise reoxidize Fe(II). With the guaiacyl lignins, hydrogen pero
xide was probably not consumed and both velocity and initiation of Fe(
III) reduction was strongly delayed in relation to the amount of added
spruce lignin or coniferyl alcohol lignin (DHP).