Proposal Process

1. Enzymatic depolymerization. Enzyme-mediated depolymerization of lignocellulose to free sugars is limited by feedback inhibition of polysaccharide depolymerizing enzymes by free sugars and other compounds found in lignocellulosic hydrolysates such as lignin fragments. We would welcome proposals directed towards obtaining additional insights into mechanisms of enzyme inhibition as well as proposals that explore reactor designs that might alleviate inhibition by separating sugars and other inhibitors from enzymes and partially digested biomass.

2. Enzyme recycling and longevity. One approach to reducing the cost of enzymes in lignocellulosic biofuel production is the use of continuous saccharification processes together with enzyme recycling. This requires the selection of long-lived, stable enzymes rather than the current focus on highly active enzymes. We would be interested in a deeper understanding of enzyme performance criteria in this context and in methods to identify and develop suitable enzyme cocktails.

3. Fermentation engineering. The EBI supports a number of research activities that are directed towards enabling continuous processes for the production of biofuels from lignocellulose. We would welcome proposals on topics that concern the design and operation of reactors or other unit operations that could expand the options for process design. For example, we envision that it might be possible to design plug flow reactors in which a microbial species at the inlet side of a reactor converts glucose to fuel and then, at a second stage, a different species converts the other sugars such as xylose to fuel. We would also be interested in biobased, chemical, or mechanical technologies that might allow two or more types of microorganisms to be maintained at optimal density in the same fermentor in an integrated conversion process.

4. Fermentation Hygiene. A core problem associated with continuous fermentation is contamination of fermentors with organisms that do not produce the desired product or that impair the growth of the fermenting organisms (e.g., phage in the case of bacterial fermentations). We welcome proposals directed toward novel solutions to such problems. Yeast and Clostridial fermentations are of particular interest.

5. Microbial longevity. The implementation of a continuous anaerobic fermentation for bioconversion of sugars to fuels may be limited by the viability of microbial cells under such conditions. We are interested in exploring the possible use of adjuvants, genetic modifications, or other approaches that extend viability under such circumstances. The organisms of primary interest are yeast and Clostridial species.

6. Improving the productivity of Clostridial fermentations. Current challenges in Clostridial fermentations include both the total time required for fermentation as well as the final titers achieved. We are interested in methods to improve the basic productivity of Clostridial fermentations as well as in approaches to make the fermentation a continuous process. This includes methods for selection/evolution and engineering of Clostridial strains, methods to alleviate butanol toxicity, advanced fermentation reactor and product separation process design.

7. Clostridial physiology. The Clostridial species that produce acetone, butanol, ethanol (ABE) only do so during a specific phase of cellular development on the pathway of spore formation. We would be interested in proposals directed toward genetic modifications that may allow more control of the developmental states. For instance, it would be useful to have externally triggered conversion from the acidogenic to solventogenic phase and the ability to hold cells in the solventogenic phase indefinitely.

8. Substrate diversity in Clostridia. We are interested in understanding the range of biological substrates that could be fermented by various Clostridial species in the context of the ABE fermentation process. We are also interested in the domestication/industrialization of Clostridial species of interest.

9. Solvent extractants. EBI investigators have recently described a process for production of diesel-like molecules derived from microbial production and extraction of acetone, butanol and ethanol (Integration of Chemical Catalysis with Extractive Fermentation to Produce Fuels, Pazhamalai Anbarasan, Zachary C. Baer, Sanil Sreekumar, Elad Gross, Joseph B. Binder, Harvey W. Blanch, Douglas S. Clark, and F. Dean Toste, Nature, doi: 10.1038/nature11594, November 8, 2012). A key feature of the process for separating the products from the fermentation broth is the use of chemical extractants. We are interested in the possibility of identifying improved extractants that have lower boiling points than the currently available extractants but retain the low toxicity, low unit cost, and useful partition coefficients of the currently available extractants (e.g. oleyl alcohol, tributyrin).

10. Global bioenergy inventory. We would be interested in proposals directed toward a techno-economic analysis of what the first 100Ej of sustainable bioenergy might look like. Aspects of the projection might include consideration of feedstocks, type of energy, carbon footprint, social effects, spatial distribution and related matters. The analysis should include consideration of the rate at which the commercial build-out could occur based on realistic assumptions of cost, capacity, competition and policy.

11. Forest biomass. We seek to expand the analysis on opportunities that may exist to sustainably utilize woody biomass for bioenergy applications while decreasing the net GHG emissions attributed to energy production. Proposals in this area should be complementary to ongoing EBI research in this general area

12. Biosouring. Current practices for secondary recovery of petroleum from reservoirs is sometimes associated with “souring” of reservoirs (i.e., the production and release of hydrogen sulfide from the reservoir). Such souring is believed to be a biological process. We would welcome proposals directed towards the development of technologies that might prevent or alleviate souring of reservoirs.