GLBRC's Publications


Our researchers consistently turn out new and innovative research that can lead to publications and new technology. On this page we'll highlight new research publications and/or activities in the GLBRC that underscore the great work that our researchers are doing.

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.

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

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.

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.

Adding cover crops to annual maize production systems did not enhance predator communities. And predation levels remained low in comparison to perennial bioenergy crops. 

OptSSeq (Optimization by Selection and Sequencing) is a newly developed approach to identifying optimally balanced enzyme levels in synthetic biofuel production pathways. This method couples selection of enzyme expression levels with high-throughput gene sequencing to track enrichment of gene expression elements from a combinatorial library.    

To explore the genetic architecture of flowering time, we developed a recombinant inbred line population from a cross between two diverse accessions of the grass Brachypodium distachyon that have different flowering behavior. We then used a genotyping-by-sequencing approach to identify six quantitative trait locis that control differences in flowering time.

We performed genome-wide association studies to characterize the genetic architecture and genes underlying flowering time regulation in switchgrass. We then identified association with flowering time at multiple loci, including in a homolog of the gene FLOWERING LOCUS T and in a locus containing the gene TIMELESS, a homolog of a key circadian regulator in animals.

We collected sorghum stem RNA-seq transcriptome profiles and composition data for approximately 100 days of development beginning at floral initiation. Our analysis identified more than 200 differentially expressed genes involved in stem growth, cell wall biology, and sucrose accumulation.

The production of fuels from lignocellulosic biomass can play an important role in reducing our dependence on fossil fuels while meeting an increasing energy demand. In an effort to meet these goals, regional biomass processing depots have been introduced as a way to improve the biomass supply network.

Excess sugars made during periods of drought are converted to inhibitors during biomass pretreatment.

The electrochemical oxidation of alcohols is a major focus of energy and chemical conversion efforts, with potential applications ranging from fuel cells to biomass utilization and chemical synthesis. 

Formaldehyde addition during biomass pretreatment leads to near-theoretical yields of lignin monomers.  

With a sensitive analytical method for diagnostically detecting incorporation of chemically labile ester bonds introduced into lignin polymers by augmenting the prototypical monomers with monolignol ferulate conjugates (“zip monomers”), we reexamined the lignin of three plants known to produce such conjugates in their extractives and found that these plants also used monolignol ferulate conjugates in their lignification. This discovery prompted a survey of a set of plants representing spermatophytes or “seed plants,” including 13 gymnosperms and 54 angiosperms.  

A stress-tolerant yeast strain was evolved for enhanced xylose utilization under aerobic or anaerobic growth conditions, the causative mutations identified by whole-genome sequencing, and systems-level effects of the mutations on cellular metabolism were analyzed. Rapid xylose utilization was found to be dependent upon genetic interactions among four genes, uncovering a surprising connection between Fe-S cluster assembly and cell signaling that facilitates aerobic respiration and anaerobic fermentation of xylose. 

We measured soil N2O emissions, CH4 uptake, NO3- leaching, and soil organic carbon accumulation for switchgrass under various N fertilizer rates over a three-year period after establishment. We found for annual N2O emissions by fertilizer rate an exponential increase that was stronger every year, and also that switchgrass yields became less responsive each year to N fertilizer. Nitrate leaching also increased exponentially in response to added N, but methane uptake and soil organic carbon didn’t change detectably. Overall, N fertilizer inputs at rates greater than crop need curtailed the climate benefit of ethanol production almost two-fold, from a maximum mitigation capacity of −5.71 ± 0.22 Mg CO2e ha−1 yr−1 in switchgrass fertilized at 56 kg N ha−1 to only −2.97 ± 0.18 Mg CO2e ha−1 yr−1 in switchgrass fertilized at 196 kg N ha−1. Minimizing N fertilizer use will be an important strategy for fully realizing the climate benefits of cellulosic biofuel production.