Poster Presentation 1B-40

The Effect of Lignin Modifying Enzymes on the Molecular Weight Distribution of Kraft Lignin

Stephen R. Decker1*, Aarti Gidh2, Michael E. Himmel1, Todd B. Vinzant1

1National Bioenergy Center

National Renewable Energy Laboratory

1617 Cole Blvd., Golden, CO 80401

Phone: 303-384-7759; Fax: 303-384-7752; E-mail: HYPERLINK "mailto:steve_decker@nrel.gov" steve_decker@nrel.gov

2Department of Chemical Engineering

University of Mississippi, University, MS 38677

Lignin, second only to cellulose as a source of fixed carbon in the biosphere, is generally considered to be highly resistant to rapid biological degradation. White rot fungi, the primary lignin decomposers, produce various extracellular redox enzymes and electron transfer mediators, which are thought to facilitate degradation of polymeric lignin. Although the enzymes, such as lignin peroxidase, manganese-dependent peroxidase, and laccase are extracellular, confirmation of direct enzyme-lignin interaction is unclear. Enzyme-mediated electron transfer from lignin molecules to oxidized cofactors such as Mn+3 and H2O2 is thought to be enhanced by the ability of these low molecular weight compounds to penetrate the wood ultrastructure and carry out oxidation of lignin in situ, where steric hindrances make direct enzyme interaction unlikely. Laccase in particular has been implicated in the mediation of both depolymerization of high molecular weight lignin and polymerization of lignin and lignin precursors. In this study, we use high-pressure size exclusion chromatography (HPSEC) coupled to multi angle laser light scattering (MALLS) detection to determine the effect of several enzymes and cofactors on the molecular weight distribution of treated kraft lignin