S6: Better bugs meets better biomass: potential of synergies of superior bioconversion microorganisms and improved biomass sources

The eventual success of the evolving biobased economy revolves around the cost-effective conversion of biomass-derived substrates to marketable products. Intensive world-wide research over the last three decades has made considerable progress developing cost-effective processes for fermentative production of fuels and chemicals with the test bed product being ethanol, with progress starting for new fuels and chemicals. Pretreatment processes that allow biomass to be accessible to enzymatic hydrolysis have evolved to provide numerous options for the variety of available plant materials. Similarly the fermentation process has evolved from complex multi-tank, multi-microorganism, multi-enzyme schemes to a one pot process called consolidated bioprocessing (CBP) where the fermentative microorganisms produce their own biomass hydrolytic enzymes. Companion to these “better bugs” is the significant progress in the last few years to developing improved biomass crops that are more readily converted by existing bioconversion processes due to their lower recalcitrance. We will discuss recent progress to merge the better bugs with the improved crops using both conventional yeast-based biomass fermentation processes plus CBP microorganisms such as Clostridium thermocellum, and highly thermophilic Caldicellulosiruptor strains. Improved feedstock work involves genetically down-regulated lines of switchgrass (Panicum virgatum) that show significant potential as well as initial research evaluating natural variants of the cottonwood tree, Populus trichocarpa. Results will show the better bugs can benefit from the better biomass, including over a third more fermentation product on a substrate weight basis, but not without potential bioconversion issues that may require further modifications in the fermentative microbe and/or process design.