Kenneth E. Hammel

Picture of Kenneth E. HammelAssociate Professor of Bacteriology
1 Gifford Pinchot Drive
Phone: (608) 231-9528
Email: kehammel@wisc.edu
Overview · Publications

Education

A.B. 1974 University of California-Berkeley
Ph.D. 1982 University of California-Berkeley
Postdoctoral Research: Philipps-Universitaet, Marburg, Germany; University of Wisconsin-Madison

Areas of Study

Lignocellulose biodegradation

Research Overview

The goal of our research is to characterize lignocellulose degradation by fungi. Because fungal attack on lignocellulose is chemically complex, we simplify the reactions that occur by using well-characterized model substrates that we design and prepare with specific isotope substitutions. Radiochemical and NMR techniques then allow us to determine which degradative reactions occur in vivo. Once key metabolites have been characterized, we attempt to identify extracellular fungal agents that duplicate the reactions in vitro.

We have shown that diverse fungal systems for lignocellulose degradation share a unifying feature: they use extracellular one-electron chemistry to oxidize target molecules to unstable free radicals, which subsequently undergo oxygenation or decomposition. Although these mechanisms are intended to work on lignocellulose, they are so nonspecific that they also accomplish a wide variety of xenobiotic oxidations.

For example, we find that the wood decay basidiomycete Gloeophyllum trabeum degrades recalcitrant polymers with oxidants that are generated via quinone redox cycling. This fungus produces the metabolite 2,5-dimethoxy-1,4-benzoquinone, reduces it with an intracellular NADH-linked flavoprotein reductase, and releases the resulting hydroquinone into the extracellular medium. The hydroquinone then reacts non-enzymatically with extracellular Fe3+ to generate radical oxidants. Detailed characterization of the reductase and the gene that encodes it is now complete.

Activities