Great Lakes Bioenergy research consistently results in new discoveries and new technologies. Here, we highlight high-impact research from all three of our research areas.
Dynamics of gene expression during development and expansion of vegetative stem internodes of bioenergy sorghum
Bioenergy sorghum accumulates 75% of shoot biomass in its stem internodes. To identify genes and molecular mechanisms that modulate the extent of internode growth, we conducted microscopic and transcriptomic analyses of four successive sub-apical vegetative internodes representing different stages of internode development of the bioenergy sorghum genotype R.07020.
Combining genome-scale experimental and computational methods to identify essential genes in bacteria
We used transposon sequencing (Tn-seq) to identify essential genes in the bacterium Rhodobacter sphaeroides under several growth conditions. We then used that data to evaluate and refine an existing genome-scale metabolic model, providing more precise systems-level understanding of the diverse metabolic lifestyles of this bacterium.
To better understand flowering time control in temperate grasses, we sought to identify which genes prevent a grass from flowering until it has undergone prolonged cold exposure. After screening for and identifying mutants in the grass species Brachypodium distachyon, we identified a mutant that flowers rapidly without cold exposure and described and characterized a new gene we named REPRESSOR OF VERNALIZATION1 (RVR1).
Microbial production of lipids in high yield presents a significant challenge, often falling short of what can be theoretically obtained. This study characterized high-lipid mutant variants of Rhodobacter sphaeroides and showed that alterations to the bacterial cell envelope can result in increased accumulation of lipids relative to the parent strain.
Researchers show that the three main components of plant biomass can be converted to high value products in economically favorable yields when using the solvent gamma-valerolactone (GVL) to break apart the biomass.
Biomass pretreatment remains an essential step in lignocellulosic biofuel production, largely to facilitate the efficient removal of lignin and increase enzyme accessibility to the polysaccharides There have been significant efforts in planta to reduce lignin content or modify its composition to overcome the inherent recalcitrance
Saccharification of thermochemically pretreated cellulosic biomass using native and engineered cellulosomal enzymes
Pretreating lignocellulosic biomass using microbes such as C. thermocellum enables a one-pot process for breaking down sugars and fermenting those sugars for fuel and chemicals. In this study, we examined the bacterium’s efficiency in breaking down cellulose in industrially relevant pretreated biomass, finding that pretreatments that remove both lignin and hemicellulose can help improve the specific activity of the bacterium’s cellulosomal enzymes.
Suppression of the lignin biosynthetic gene CCR1 results in decreased lignin recalcitrance and increased digestibility
In this study, we examined features of a lignin biosynthetic mutant in maize that we hypothesized could result in an increase in the levels of more readily cleavable ester bonds (“zip-lignin”) in the lignin backbone. The maize ccr1 mutant displayed reduced total lignin content with no growth penalties, higher zip-lignin levels, and higher levels of sugar release.
To help identify better management practices for more productive bioenergy cropping systems, we used two switchgrass sites to investigate the causes of biomass loss over time, and identified plant components contributing to nitrogen (N) loss or retention at different harvest times.
Depolymerizing lignin, the complex phenolic polymer fortifying plant cell walls, is challenging, making lignin a major barrier to gaining access to stored energy in lignocellulosic materials. Here we reveal unprecedentedly rapid lignin depolymerization and degradation in an ancient fungus-cultivating termite system; we combine laboratory-feeding experiments with step-wise structural and chemical analyses performed while the woody material is digested in this symbiotic system.