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Prospecting in the rainforest to develop biofuel technology

Plant biomass is the most abundantly available source of renewable energy on Earth. Most of this energy is stored as lignocellulose, a polymer that is the structural building block for plants. Some bacteria are able to convert (or decompose) lignocellulose to biofuels. Bacterial communities in tropical forest soils exhibit some of the highest decomposition rates in the world. We study these soil microbiomes to understand and identify efficient and cost-effective processes for renewable energy production from plants.

Lignocellulose is typically 15-28% of the total dry weight of plant biomass, it represents a significant unutilized source of carbon for biofuels. A recent joint analysis by the DOE and USDA shows that there is sufficient national supply to make lignocellulosic biofuels technically feasible. The use of lignocellulose as a renewable energy source has many advantages--above all, lignocellulose production is domestic and independent of food agriculture.

The decomposition of plant biomass is a key first step in the conversion of plant lignocellusose to sugars and then to biofuels. One of the biggest barriers to efficient lignocellulose deconstruction is that lignin both blocks the action of cellulases (enzymes that break down cellulose to sugars) and produces wasteful by-products. Unfortunately, this first step has posed a great challenge to making biofuels economically viable. By characterizing anaerobic lignin degradation in bacteria, we may be able to incorporate these enzymes and pathways into metabolic engineering of biofuel- and biodiesel-producing bacteria.

Tropical forest soils exhibit some of the highest lignocellulose decomposition rates in the world. Fast rates of decomposition in highly active and biodiverse tropical forest soils could be informative for improving lignocellulose deconstruction in development of next generation biofuels, where bacterial dominance in anaerobic lignin and cellulose degradation could provide insight into plant-based biodiesel development. As part of this project we are characterizing bacteria isolated based on their ability to grow anaerobically with lignin as the sole carbon source, as well as consortia of simplified communities adapted to grow anaerobically on lignin as sole carbon source.

Using proteomics and transcriptomics, we have shown that the anaerobic lignin-degrading bacterium Enterobacter lignolyticus SCF1 was able to degrade lignin anaerobically using both dissimilatory and assimilatory mechanisms, meaning that the organism was both “eating” and “breathing” lignin to grow. This work has been recently published in Frontiers in Microbiology (PMID: 24065962).

 

PI: Kristen DiAngelis

 

 

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