Recombinant Lignin Deploymerase with Enhanced Stability and Catalytic Activity

Lignin - the basic unit of xylem and strengthening elements in wood, is made up of polymerized phenylpropane units. Its interwoven covalent structure makes it strong, inflexible and resistant to degradation. Indeed, the degradation of lignins in nature, a process engendered pre-eminently by white-rot fungi, is so slow that it represents the rate-limiting step in the carbon cycle. A complete understanding of the mechanism of lignin biodegradation is expected to have a profound impact upon the efficiency of biomass utilization.
A white-rot fungal enzyme, lignin depolymerase, has been isolated at the University of Minnesota for the first time that is capable of degrading high molecular weight lignin components. The proposed work aims to produce a recombinant lignin depolymerase with enhanced catalytic activity and thermostability that is suitable for applications in biorefineries where the lignocellulosic polysaccharides are degraded enzymatically. Since lignin depolymerase is naturally produced by white-rot fungi in extremely low concentrations, the gene encoding the enzyme will be cloned and expressed at much higher levels in a suitable host organism. The catalytic properties of the recombinant enzyme will be improved through directed evolution strategies employing error-prone PCR and saturation mutagenesis at codons for particular residues in the polypeptide chain.

We would also like to acknowledge our co-PI: Simo Sarkanen.

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Last Updated: 9/18/06