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.
Developmental regulation of processes, pathways, and genes that affect stem growth and composition in sorghum
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.
The effects of variable precipitation on downstream processing and fermentation of biomass to biofuels have not been well studied. This study demonstrates that increased plant soluble sugars produced during drought stress are made into pyrazines and imidazoles during ammonia-based pretreatment and are inhibitory to microbial growth.
We report that using formaldehyde to stabilize lignin during extraction leads to near-theoretical yields of lignin monomers after hydrogenolysis of the extracted product. These yields were three to seven times higher than those obtained when using the analogous method without formaldehyde.
Yeast evolved for enhanced xylose utilization reveal interactions between cell-signaling pathways and iron-sulfur cluster biogenesis
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.
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.