Refreshments served at 11:15
After briefly reviewing the strategic rationale for cellulosic biofuels, data will be presented from a comprehensive recent study aimed at evaluating the cumulative and relative impact of "multiple levers" to overcome the lignocellulose recalcitrance barrier, including choice of biocatalyst and feedstock, genetically modified plants and less recalcitrant natural variants, and several non-biological approaches to augment the deconstruction process. Anaerobic thermophilic bacteria are found to be decisively more effective than industry-standard fungal cellulase at solubilizing cellulosic biomass under a broad range of conditions. However even the best plant cell wall-solubilizing biocatalysts require some assistance in order for lignocellulose to be processed with high yields in a reasonable amount of time. As an alternative to thermochemical pretreatment, we are investigating physical disruption once fermentation is initiated – termed cotreatment. Results presented include: a) demonstration of fermentation in the presence of physical disruption at an intensity sufficient to substantially increase lignocellulose solubilization, b) high extents of solubilization comparable to conventional pretreatment, c) lignin residues with less modification than result from thermochemical pretreatment. Taking advantage of the outstanding capability of thermophilic anaerobic bacteria to ferment cellulosic biomass without added enzymes requires that metabolic engineering tools be developed and applied to these organisms in order to bring product yields and titers to industrially acceptable levels. Recent progress will be described involving the cellulose-fermenting Clostridium thermocellum as well as hemicellulose-utilizing thermophiles such as Thermoanaerobacterium saccharolyticum. Thermophilic consolidated bioprocessing with cotreatment represents a nascent alternative to the conventional processing paradigm involving thermochemical pretreatment and added fungal enzymes. Recently-published technoeconomic analysis indicates potential for an 8-fold shorter payback period and feasibility at 10-fold smaller scale compared to technology based on the current processing paradigm.
Lee Lynd is the Paul and Joan Queneau Distinguished Professor of Engineering and Adjunct Professor of Biology at Dartmouth College, Consolidated Bioprocessing Team Lead at the US Department of Energy Bioenergy Science Center, Executive Committee Chairman of the Global Sustainable Bioenergy Initiative and Co-Founder and Director of Enchi Corporation. He is a fellow of the National Academy of Sciences, and recipient of the Lemelson-MIT Sustainability Prize for inventions and innovations that enhance economic opportunity and community well-being while protecting and restoring the natural environment, the Charles D. Scott award for distinguished contributions to the field of biotechnology for fuels and chemicals, and two-time recipient of a Charles A. Lindbergh grant in recognition of efforts to promote a balance between environmental preservation and technological advancement.