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.
Plants have convergently evolved to use "zips" (chemically labile ester linkages) in their lignin polymers
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.
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.
This study showed that applying nitrogen (N) fertilizer to the cellulosic biofuel crop switchgrass has the potential to cause an exponential increase in nitrous oxide (N2O) emissions, a major greenhouse gas. N fertilizer therefore has the potential to curtail the climate benefit of cellulosic biofuel production.
The flowering of many plant species is coordinated with seasonal environmental cues such as temperature and photoperiod. In winter wheat and barley, three genes – VRN1, VRN2, and FT – form a regulatory loop that regulates the initiation of flowering. Here, we test whether the circuitry of this regulatory loop is conserved across Pooid grasses. Our studies reveal that some aspects of the regulatory loop, such as the cold repression of VRN2, are unique to wheat and barley. However, this study, as well some of our previous work, demonstrates that VRN2 is a repressor of flowering that functions broadly in grasses from rice to Brachypodium, and thus VRN2 is a target for fine tuning of flowering in grass biofuel crops.
This study aimed to elucidate the incorporation pathways of tricin into maize lignin by applying liquid chromatography-mass spectrometry-based tools developed for oligolignol profiling. Twelve tricin-containing products (each with up to eight isomers) were observed and authenticated by comparisons with a set of synthetic tricin-oligolignol dimeric and trimeric compounds.
This study assessed the possibility of producing reliable predictions for genomic selection using a small sample size of two different switchgrass populations genotyped by exome sequencing and tested in two different locations for three important agronomic traits: biomass yield, plant height, and heading date (flowering time). We assessed various prediction procedures, differing by prediction model and also by type of marker-data transformation.
As a feedstock for biomass-to-biofuel processes, woody biomass exhibits several advantages that facilitate logistics relative to herbaceous feedstocks, including year-round availability and high bulk density. As we envision biomass-to-biofuel processes that include diverse biomass feedstocks, the physical and chemical properties of said biomass will have an important impact on the conversion process.
In order to determine the structural basis for stereospecificity of bacterial enzymes involved in lignin bond cleavage, crystal structures of the enzymes involved were solved and the corresponding biochemical analyses for these proteins were performed. The detailed structural and biochemical characterization of LigE and LigF in this study,1 and the corresponding detailed structural and biochemical characterization of other members of this lignin degradation pathway (LigD, LigO, LigL, and LigG) in a second study,2 reveal important new aspects of the enzyme mechanisms and the determinants of substrate specificity.
To gain insight into how Bayberry fruits produce the highest amount of surface lipid known in nature, the authors examined the chemical and morphological development of the Bayberry wax layer, monitored its biosynthesis through radiolabeling studies, and identified transcripts for enzymes and proteins expressed during Bayberry surface wax production. The biochemical and expression data together indicate that Bayberry surface glycerolipids are synthesized by a pathway for triacylglycerol synthesis that is related to cutin biosynthesis, rather than conventional triacylglycerol assembly.
Mechanism of imidazolium ionic liquids toxicity in saccharomyces cerevisiae and rational engineering of a tolerant, xylose-fermenting strain
The method to deconstruct lignocellulosic biomass using ionic liquids (ILs) is a promising technology that can bypass expensive enzymatic pretreatments that are commonly used. A potential limitation to adoption of ILs for bioconversion is that residual IL solvent is toxic to microbes and can impede fermentation of biomass to biofuels. A technique called chemical genomics was used to identify yeast genes that confer sensitivity or resistance to IL, allowing researchers to identify a cellular substructure called the mitochondrion as the apparent target of IL toxicity. Targeted deletion of a gene identified from the chemical genomics screen in a xylose-fermenting strain of yeast greatly increased its IL tolerance, biomass-derived sugar conversion, and yields of ethanol.