The need for a sustainable, renewable source of transportation fuels has been recognized for a long time; however, the availability of inexpensive oil has largely obscured the urgency for its development. Recent political and economic events have highlighted the fragility of our dependence on foreign oil and reinvigorated a longer-term perspective on the need to provide a sustainable source of domestically-produced transportation fuel. Many fuel production alternatives are being proposed, ranging from purely thermochemical, to hybrid and to entirely biological production. As potential concedes to process performance, economics will sort out the best production options.
For the 2007-08 academic year, Dr. Curtis went on sabbatical, in which he (1) consulted as a technical advisor for Green Fuels, one of the first algae biofuels companies, and (2) immersed himself in the techniques of molecular biology. Since then, genetic engineering has become a staple of the CurtisLab 'toolkit'. With CurtisLab's long history of work in plant propagation and early entry into the world of algae biofuels, research in cellulosic biofuels--- or as Curtis explains it CurtisLab's 'sticks-to-fuels' work---was a natural evolution in seeing plants from 'Cradle to Grave'. Dr. Curtis has given invited talks on this theme, encompassing his full spectrum of research, respectively in 2014 at Arkansas' (P3) Center for Plant Plant Powered Production and i
n 2015 at Pacific Northwest National Lab (PNNL).
Figure 1. A small piece of paper with the words "Eat Me" written on it in a Clostridium phytofermentans culture degrading over time.
One of the main products of C. phytofermentans cellulose hydrolysis and fermentation is ethanol.
In part as a response to our work in metabolic engineering, in which our metabolic engineering review points out that despite over 30 years of global research and huge investment in the field, native biology is still orders of magnitude more productive than any constructs derived through metabolic engineering (see above). Therefore, our approach to cellulosic fuels took a 'division of labor' or DOL approach, wherein the labor of (1) breaking down biomass and (2) converting biomass into fuel is divided between multiple organisms. Specifically, Clostridium phytofermentans, obligately anaerobic, degrades lignin to make cellulose more accessible while yeast, a facultative anaerobe, converts the biomass into fuel. In the process, we have studied the biofilm behavior of cellulytic C. phytofermentans. Tangential efforts
have included variations on this consortia, including one engineered to consume syngas, and a collaboration with PSU Prof. Seong Kim to use SFG (Sum Frequency Generation) spectroscopy to compare 'white-rot' fungi (i.e. Phanerochaete chrysosporium and Ceriporiopsis subvermispora) to accomplish pre-treatment of biomass by consuming lignin to make the cellulose more accessible.
Synergistically taking advantage of other areas of CurtisLab's expertise, CurtisLab partnered with Dr. Andrew Tolonen, with whom Dr. Curtis had shared a lab bench during his sabbatical at Harvard, and Dr. Mohandass Ramya to evolve a more ethanol-tolerant strain of C. phytofermentans as well as metabolically-engineer for increased ethanol production. Similarly, we are also translating this success into introducing metabolic pathways to bypass ethanol fermentation for preference to instead produce hydrocarbons.
In line with CurtisLab's philosophy of sustainability and long history of low-cost, scaleable technology this 'sticks-to-fuel' consortia has the ultimate goal of a simplified process that can be scaled down to an 'on farm' fuel production system to minimize costs associated with biomass transport. Similar to our Hydrostatically-powered Temporary Immersion Bioreactor (Hy-TIB) for plant propagation, We are also interested in utilizing low-cost bioreactor design and operational principles. In particular, we had developed a plastic-lined bioreactor to facilitate a low capital investment process paradigm.
Dr.Curtis (bottom left) pictured adjacent
to mammoth grain silos...that could potentially
be retooled for on-farm pretreatment.
Researchers: Trevor Zuroff, Salvador Barri Xiques, Rachel Fore, Ramya Muhandass, Stephen Rossi, Taylor Maher, Patrick Hillery, Gabriel Paulo de Souza, Michael Hough, Rachel Kopperschmidt, Kevin Dazen, Alex Rajangam.
Collaborators: Susan Leschine, Tracy Nixon, Andrew Tolenen, Seong Kim, Nick Winograd, Mohandass Ramya
Bill Muzika, Nymul Khan, Trevor Zuroff, Wayne R. Curtis. Feedstock Flexibility in Biofuel Production. AIChE Regional Conference, U. Maryland, College Park, MD, Apr 11, 2015.
Zuroff, Trevor. Engineering a microbial consortium for lignocellulosic biofuel production. Dissertation. Penn State University: University Park, PA (2014).
Hillery, Patrick. The Process Design and Economic Analysis of a Farm-scale System for Producing Ethanol and Hydrocarbon (botryococcene) Fuels from a Lignocellulosic Substrate. Dissertation. Penn State University: University Park, PA (2014).
Maher, Taylor. Application of two different fungal species for biological pretreatment in an integrated lignocellulosic biofuels paradigm. Dissertation. Penn State University: University Park, PA (2014).
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