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The Science and Engineering for a Biobased Industry and Economy

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Principal Investigator/Project Leader: 
Department of Project: 
Department of Microbiology
Project Description: 

Only 10 years ago the "brown rot" wood degrading fungi were considered to be poorly evolved organisms in the fungal world. It was known that they lacked many of the enzymatic systems that the taxonomically more numerous "white rot" wood degrading fungi possessed, and it was thought that the brown rot fungi just had not yet reached a stage of evolution to produce these enzymatic systems. In essence, they were thought to be more primitive fungal organisms. However, new genomic analyses conducted over the last 7-8 years have turned this thinking on its head. Through "molecular clock"analysis it is now known that

the brown rot fungi evolved from early progenitors of the white rot fungi, and curiously the brown rot fungi lost many of the enzymatic systems that many researchers have considered to be some of the most important in biomass conversion. While losing these enzymatic systems however, these fungi also gained a new non-enzymatic mechanism that generates highly damaging "free radicals" which are able to efficiently deconstruct (or decay) wood. This system which is known as the "Chelator-mediated Fenton" (CMF) system and is unique in all of nature in that it appears to occur only in a few select Families of the

brown rot fungi. Evidence suggests that abandoning the physiologically expensive system of producing enzymes for the "deconstruction" of woody materials has been successful for the brown rot organisms. Even though they are represented by relatively few species as they have evolved relatively recently from the the white rot fungi, the brown rot organisms dominate in the coniferous ecosystems of North America. They decay the dead softwood debris found in those forests very efficiently, and largely without the aid of "extracellular" enzymes.

Although considerable research has been performed focused on the conversion of biomass to useful products, to date we still have no functional bio-refineries in the US or globally. One of the key problems in the conversion of biomass is known as the "lignin recalcitrance barrier". Lignin is a tough "plastic material" produced by plants that, at the molecular level, coats the "cellulosic" components of biomass that are used to produce most bio-based products and biofuels. Currently some very harsh chemical and heat pre-treatment systems that release cellulosic components from the surrounding lignin barrier are used in pilot scale research for most bio-refineries. To date however, these have been shown to be so harsh that they either damage the cellulose components, they are so polluting that they generate problematic or hazardous wastes, or they simply are so expensive that they cannot be used practically. What our research focuses on is harnessing and utilizing the CMF system that was developed millions of years ago by fungal organisms (a system that has largely been ignored by most scientists interested in biomass conversion). We hope that by harnessing the system that these unique "brown rot" fungi have evolved over the millennia that we can mimic and apply their chemistries to produce biorefinery systems that are more effective, and in particular that are highly energy efficient, cost efficient, safe and non-polluting.

Our goals in this research are to better understand the CMF mechanism, and how and why it evolved and is used in the brown rot fungi. Further, we want to understand how the CMF system generates the damaging "free radicals" so efficiently as to destroy (or deconstruct) wood, while also not damaging the fungus. Through a better understanding of the CMF mechanism, we then have planned a series of experiments to apply the chemistries in pilot scale studies on woody biomass to convert wood

to useful substrate material that could be used downstream to for the production of useful feedstock chemicals and bioenergy. Circumvention of the "ligin recalcitrance barrier" is the key to making all this happen, and the brown rot fungi have spent millions of years developing a system to do just this. If we can better understand how they do this, we can develop better bioprocessing systems that avoid the high temperatures, expensive chemistries, hazardous treatments/pollutants that current biorefinery pretreatment systems require.

Topics: 
Energy topics: 
Biomass/ Biofuels