Research Highlights

GLBRC researchers processed and experimentally quantified ethanol production from five different herbaceous feedstocks: two annuals (corn stover and energy sorghum) and three perennials (switchgrass, miscanthus, and restored prairie). They determined that a range of plant types could be used in a lignocellulosic ethanol refinery without having a major impact on field-scale ethanol yield, which represents the ethanol production per land area.

In this study, GLBRC researchers tested the hypothesis that microbial communities could be used to produce valuable compounds, such as medium-chain fatty acids (MCFAs), from lignocellulosic stillage. Techno-economic analyses showed that, at the productivity of MCFAs achieved in this study, valorizing lignocellulosic ethanol stillage to MCFAs could improve the economic sustainability of a biorefinery.

Unlike harvest of corn stover, which is linked to grain harvest, timing of harvest for energy grasses such as switchgrass is relatively flexible. In this study, GLBRC scientists aimed to determine if switchgrass harvest could be timed to maximize beneficial impacts on fermentation while avoiding production of harmful degradation compounds.

As plant breeding programs embrace the idea of the biorefinery, lignin is emerging as a potential feedstock for commodity chemicals. To improve our understanding of lignin’s chemical structure and find potential bioproducts in lignin, GLBRC researchers developed a powerful analytical method to identify new and low-abundance compounds within the complex lignin biopolymer.

Comprehensive information about bioenergy crops’ composition under field conditions is needed to design optimal systems for production, harvesting, storage, and biorefinery operations. In this study, GLBRC researchers used near-infrared spectroscopy and nuclear magnetic resonance spectroscopy to characterize the composition of the energy Sorghum bicolorhybrid TX08001 grown in irrigated and non-irrigated field conditions, providing baseline information for future optimization.

Optimizing how we break down biomass is critical to developing valuable chemicals from renewable materials such as plant lignin. GLBRC researchers found that the bacteria Novosphingobium aromaticivorans rapidly breaks the β-aryl ether bond commonly found in lignin, and that its enzyme, a Nu-class glutathione S-transferase, performs the critical step of removing the antioxidant glutathione.

Grass species, which are among the major renewable feedstocks supporting biofuel production, can provide an abundant source of mixed-linkage glucan (MLG), a glucose polymer. Improving biofuel crops by increasing sugar yields requires a thorough understanding of biosynthetic mechanisms. In this study, GLBRC researchers demonstrated that MLG is present in the Golgi apparatus, in post-Golgi structures, and in the cell wall; these findings provide new insight on how to modify the localization of MLG synthase to maximize production of MLG.

The copper-catalyzed alkaline hydrogen peroxide (Cu-AHP) deconstruction process is highly effective at pretreating a genetically-modified type of poplar called "zip-lignin" poplar, resulting in high sugar yields for biofuel fermentation even when inputs are reduced. Zip-lignin poplar incorporates weak linkages into lignin, the hard-to-process compound that gives plant cell walls their sturdiness, rendering the poplar especially amenable to the Cu-AHP deconstruction method.

Spatial dependence, or the likelihood that nearby land units are more likely to be related than more distant ones, has effects on landowners' willingness to make land available for bioenergy production.

In this study, we used chemical genomics (CG) to identify the mechanisms of GVL toxicity to fermentative microbes. We identified gene deletions that confer sensitivity or tolerance to the solvent and then used this knowledge to engineer a xylose-fermenting yeast strain with improved tolerance to GVL and enhanced conversion of sugars to biofuel.