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.
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.
Glycoside hydrolases (GH) are enzymes that release sugar from cellulose, hemicellulose, and other polysaccharides. Understanding the specificity of GH enzyme reactions in the context of the plant cell wall is essential to providing more efficient ways to deconstruct plant biomass for biofuels production.
Co-solvent system for sugar production from lignocellulosic biomass using biomass derived gamma-valerolactone
Recovering sugars and lignin from the deconstruction solvent GVL relies on methods that are expensive or may inhibit downstream conversion of sugars to biofuels. A new method examines the use of co-solvents1 and their impact on sugar yield and economics of biofuel production.2
Improved understanding of lignin recalcitrance by defining and quantitatively determining lignin dimers
To better understand the development of plant cell walls and to improve strategies for the valorization of lignocellulosics, we identified and quantified 12 degradation products released by lignin depolymerization using newly synthesized standards.
This study tested whether we can alter cell wall attributes and plant development by augmenting the available soluble sucrose pools. To this end, we overexpressed an exogenous galactinol synthase to alter carbon allocation in hybrid poplar and then examined the effects on plant growth, carbohydrate and lignin content and composition, xylem properties, wood physical characteristics, and transcript abundance of differentially expressed genes.
The degradation of cellulose, the principal component of plant cell walls, is critical to ecosystem functioning and the global carbon cycle. The primary drivers of plant biomass deconstruction are fungi and bacteria found in the soil or associated with plant-eating eukaryotes.
Native perennial grasslands, which can be planted on marginal lands, are a potential feedstock source for lignocellulosic biofuel production. And yet more information is needed to understand how management practices such as frequency or timing of harvesting can affect their productivity and community composition.
Reducing the flavone tricin in grasses results in increased lignification and decreased digestibility
By studying a naturally silenced maize mutant defective in chalcone synthase, a key enzyme involved in the biosynthesis of flavonoids, we demonstrated that levels of tricin-related flavonoids were significantly reduced, resulting in strongly reduced incorporation of tricin into the lignin polymer. These plants also had increased total lignin content and, consequently, demonstrated significantly reduced saccharification.