Biomass Depolymerization programs

Microbiological and Biochemical Approaches to Overcome Biomass Recalcitrance - Completed

This program studied enzymatic and microbiological approaches for degradation of lignocellulose that would convert the energy-rich cellulose more efficiently to fuels. Gerlt's group obtained genome sequences for bacterial (Streptomycetes) species that degrade Miscanthus lignocellulose. With genome sequences and either an appropriate scaffold sequence from an organism that does not degrade lignocellulose or identification of oxidative enzymes that are produced/secreted in the presence of Miscanthus lignocellulose, they could identify islands of genes that encode enzymes involved in lignocellulose degradation. Characterization of these enzymes provided information to help (re)design pathways in genetically tractable organisms to facilitate lignocellulose degradation.

program Highlights

2011 Highlights

Gerlt’s group demonstrated that the SLAC (a copper-containing enzyme) is able to reconstruct ethanosolv lignin, producing higher molecular weight species. They have evidence that the net deconstruction of lignin requires interception of radical intermediates generated by the action of SLAC  (and other oxidases/peroxidases). They also found that the catalytic properties of SLAC can be altered by mutating the binding site for the T1 copper, presumably by altering the redox potential of the copper.

2010 Highlights

Gerlt’s group demonstrated that disruption of the gene encoding the “small” laccase (SLAC) from Streptomyces coelicolor produces a phenotype with compromised lignin-modifying activity.  They also demonstrated that the SLAC modifies the structure of ethanosolv lignin extracted from Miscanthus lignocelluose.  These studies are the first example of a purified bacterial “deconstruction” enzyme that utilizes lignin as substrate.

2009 Highlights

The genomic DNAs of target bacteria initially were subjected to sequence analysis at the University of Illinois Biotechnology Center using both 454 and Titanium sequencing methodologies. However, because of their high GC contents (> 70%), the group obtained a large number of contigs that could not be assembled into complete genomes. Sequencing, assembly, and annotation of these genomes began at the DOE Joint Genome Institute, with the expectation that more complete assemblies can be obtained. In parallel with genome sequencing, secretome analyses are being used to identify oxidative proteins that are secreted in response to the presence of Miscanthus lignocellulose.

 


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