Biomass Formation and Modification
Biomass Deconstruction and Conversion
Promise of Unusual Lignin Polymer as Feedstock for Carbon Fiber
Stronger, Lighter Carbon Fiber Could Be Used in Parts for Cars, Aircraft, Electronics, and Sports Equipment
BESC researchers discovered an unusual lignin polymer in the seed coats of vanilla beans (pictured) that is naturally biosynthesized from caffeyl (C) alcohol. In contrast to lignin polymers that are highly cross-linked, C-lignin is a linear polymer, which makes it easier to process into high-quality carbon fibers. [Image courtesy iStock]Read More
Identification of Poplar Adaptation Mechanisms
Findings Could Lead to More Efficient Ways of Breeding High-Ethanol-Yielding Poplar and Other Tree Species
Using whole-genome sequencing and high-throughput phenotyping, BESC researchers were able to rapidly pinpoint gene mutations responsible for causing low lignin levels in poplar trees planted in a variety of environmental conditions. This proof-of-concept will allow researchers to tag genes associated with other economically important but complex plant traits. [Image courtesy BESC]Read More
Beneficial Plant Gene Discovery
Research Lays Groundwork for New Ways of Manipulating Plants
BESC researchers discovered a previously uncharacterized gene (GXMT1), which directs a key step in the development of xylan, a principal component of cell walls in plants such as Arabidopsis (pictured). Characterizing this gene, which makes the plant resistant to biofuel conversion, will lead to improved strategies for modifying such cell wall structures to help turn plants into biofuel more efficiently. [Image courtesy iStock]Read More
Molecular Structure of Plant Biomass
Imaging Reveals Enzymes in Action and Significance of Plants' Nanoscale Architecture
Plant cell walls contain networks of cellulose microfibrils that can be broken down into sugars for fuel and complex polymers that shield the cellulose from enzymatic attack. To characterize cell wall structure at the subnanometer scale and assess its response to chemical pretreatment, BESC developed techniques to image enzyme digestion in real time, revealing that biomass reactivity is determined by the nanoscale architecture of plant cell walls.Read More
A Leap Forward in Microbial Ethanol Yields
Engineered yeast converts up to 97% of plant sugars into fuel
Scientists at BESC and research partner Mascoma LLC have developed an advanced strain of Saccharomyces cerevisiae that sets a new standard for conversion of biomass sugars from pretreated corn stover. While conventional yeast (pictured) leaves more than one-third of plant sugars unused in the form of xylose, the C5 FUEL™ microbe efficiently converts this xylose into ethanol in less than 48 hours.Read More
Real-World Performance of Low-Lignin Switchgrass
Field study assesses sugar release and ethanol yield in transgenic feedstock
Lignin in the cell walls of switchgrass and other bioenergy feedstocks severely limits the accessibility of cell wall carbohydrates to enzymatic breakdown into fermentable sugars and subsequently biofuels. In the first reported study of its kind, the biofuel potential of transgenic switchgrass with reduced lignin content was evaluated over two growing seasons.Read More
Using a "commercialization council" of technology transfer and intellectual property (IP) management professionals from partner institutions, BESC evaluates the commercial potential of new inventions arising from BESC research and promotes and facilitates the licensing of BESC IP.
BESC's education program, which is 75% self-sustaining, takes a novel approach. BESC has developed lesson plans to educate students about energy production and utilization. BESC uses a hub-and-spoke approach of working through regional science centers to maximize hands-on access and adaptation to local conditions.
Progress to Date
Dramatic performance of Clostridium thermocellum explained by its wide range of cellulase modalities
ORNL Researchers Receive INCITE Award
Interview with Dr. Jan Westpheling
January 06, 2016
Review: How Plant Cell Wall NMR Provides Insights Into Biomass Chemistry and Structures
The structure of the plant cell wall and recalcitrance are intimately tied together such that fundamental breakthroughs in recalcitrance have driven the science of biomass characterization. Work from BESC and other energy centers has dramatically enhanced the resolution and productivity of Nuclear Magnetic Resonance (NMR) analysis of biomass polymers including lignin, cellulose and hemicellulose. Whole cell NMR analysis, as reviewed in this article, provides a relatively facile means of characterizing changes in lignin and hemicellulose that contribute to reduced recalcitrance in pretreated biomass and/or transgenic or natural variant plant species.
December 14, 2015
Towards Understanding Gene Systems Mediating Redox Homeostasis and Energy Metabolism in C. thermocellum
Current moderate ethanol yields and productivities as well as growth inhibition impede industrial deployment of this bacterium for commodity fuel production. Redox imbalances may contribute to incomplete substrate utilization, limit bioproductivity, and direct fermentation products to undesirable overflow metabolites. The redox systems identified are active and fungible in C. thermocellum upon introduction of a redox stress, and considered a link between redox stress and the occurrence of ethanol yield-limiting, unwanted metabolic processes. This expression study informs ongoing metabolic engineering efforts to increase bioproductivity in C. thermocellum.
December 10, 2015
Commercial Licensing of a BESC Global Genetic Regulator of Aromatic Biosynthesis
BESC has been studying SNPs and key compositional and conversion phenotypes in the natural variation population in Populus using GWAS (genome-wide association studies). A study of rare SNPs identified an unusual paralog in Populus which had taken on new regulator functions. Patent applications have been filed. Follow-on work is testing the utility in other plant species. The technology is being licensed to two companies who plan to commercialize the technology: GreenWood Resources and Forest Genetics International. Increasing biofuel yield or forage digestibility can lead to reductions in land use for these crops and thus contributing to long term sustainability.
October 26, 2015
Integrating mRNA and Protein Sequence Data to Enable Detection and Quantitative Profiling of Natural Protein Sequence Variants in Populus
In this study, we used next-generation RNA-sequencing data to generate genotype-specific protein databases, which allowed the identification and quantification of sequence variations at the protein level. A variety of natural sequence protein variants were quantified in two Populus trichocarpa genotypes. In addition to expected neutral single amino acid polymorphisms, investigators characterized polymorphisms predicted to be non-neutral and located in regions of the genome predicted to have undergone recent positive and/or divergent selection and therefore represent a candidate list of protein variants relevant to plant adaptability.
October 16, 2015
Direct Catalytic Upgrading of Ethanol is Efficient and Works Through a Hydrocarbon Pool Mechanism
Experiments with C2H5OD and in situ DRIFTS (diffuse reflectance FT infrared spectroscopy) suggest that most of the products come from the hydrocarbon pool type mechanism and endothermic dehydration step is not necessary. This mechanism supports the slightly exothermic nature of the reactions and potentially improves the process economics.
October 13, 2015
Metabolic Model Used to Predict and Remove Redox Bottlenecks in C. thermocellum Biofuel Production
Metabolic engineering strategies have been used to enhance ethanol production in C. thermocellum, a highly effective cellulose degrader. A central metabolic model has been constructed and validated for C. thermocellum which can expedite the process of designing and testing metabolic engineering strategies. Using the model for experimental design, investigators were able to highlight key overexpression targets for metabolic engineering such as RNF, NFN, or AdhE and to predict genotypes which may enhance ethanol yield.
October 13, 2015
CELF Pretreatment Boosts Biofuel Yields and Titers
Novel Co-solvent Enhanced Lignocellulosic Fractionation (CELF) pretreatment has shown to be highly effective in achieving near theoretical sugars yields for corn stover. Earlier preliminary data also showed that CELF performs much better than dilute acid (DA) pretreatment; however, the effect of solids concentrations and enzyme loadings on ethanol yields and titers was not known. The results reported show that CELF pretreatment makes possible high ethanol yields and titers, and most importantly, at low enzyme loadings.
October 12, 2015
Molecular Dynamics Simulation Reveals Molecular Basis of Highly Efficient Lignin Solubilization
Previous BESC work has shown that pretreatment of biomass with a tetrahydrofuran (THF)–water cosolvent is highly effective at extracting lignin from biomass and achieving high yields of fermentable sugars from cellulose. However, the molecular mechanism of this effect is not known. In most aqueous-based pretreatments, lignin is not removed entirely from biomass because it aggregates onto the cellulose surface, blocking enzymatic access to cellulose. Under theta solvent conditions, polymers do not aggregate, thus providing a mechanism for the observed lignin solubilization that facilitates unfettered access of cellulolytic enzymes to cellulose. This mechanism may provide insights to improve this or other novel pretreatments.
September 22, 2015
Computational Inference of the Structure and Regulation of the Lignin Pathway in Switchgrass, Panicum virgatum
Recalcitrance is partially due to the heterologous polymer lignin. The biosynthetic pathway leading to monolignols, and thus to lignin, is not completely known in switchgrass, and difficulties associated with in vivo measurements of its intermediates pose a challenge for a true understanding of the functioning of the pathway. However, such an understanding is a prerequisite for manipulations of transgenics toward altered lignin properties and a reduction in recalcitrance. The computational analysis suggests regulatory mechanisms of product inhibition and enzyme competition, which are well known in biochemistry, but so far had not been reported in switchgrass. Our deepened understanding of the pathway allows us to make prediction regarding combined knock-downs that are likely to alter lignin properties significantly.
September 01, 2015
Engineering of a Thermophilic, Cellulolytic Microbe to Produce an Advanced Biofuel
Production of isobutanol from cellulose in minimal medium achieved 5.4 g/L titer and roughly 41% of theoretical yield. This result successfully demonstrates the advantages of using a consolidates bioprocessing approach to produce an advanced biofuel. This is a measureable and significant step towards commercially relevant titers and yields. Isobutanol can be utilized as a "drop-in" biofuel, as a substrate for upgrading into hydrocarbon fuels, or as a feedstock for other bioproducts.
September 01, 2015
Highest Yield to Date of Ethanol from Engineered Clostridium thermocellum
C. thermocellum is one of the fastest growing anaerobic organisms on crystalline cellulose. Metabolic engineering is required to increase ethanol yield by eliminating pathways to other fermentation products. Effectively eliminated lactate, acetate, formate, and most H2 production. Ethanol yield doubled relative to the wild type, both on model substrates and dilute-acid pretreated plant biomass. Allowed for higher titer ethanol production from cellulose in the absence of pH control. Highest ethanol yield achieved to date in C. thermocellum. Created platform strain for further metabolic engineering for consolidated bioprocessing.
August 29, 2015
New Insights into Regulation of Cellulosomal Xylanase Genes in Clostridium thermocellum
Clostridium thermocellum is regarded as a model cellulolytic thermophile, and can grow well on un-pretreated lignocellulosic feedstock, yet it does not utilize C5 sugars (e.g., xylose, arabinose) despite including xylanases in its cellulosome. While unable to utilize C5 sugars C. thermocellum has a set of sigma factor regulated xylanases that, when expressed in response to biomass, can increase the amount of solubilized carbohydrate including glucan.
August 27, 2015
Application of Results from Down-Regulation of Lignin in Populus and Switchgrass Leads to Similar Effects in Eucalyptus
Changes to gene expression in switchgrass and Populus have shown increased sugar release and reduced recalcitrance. This work sought to transfer results to Eucalyptus, a fast-growing warm climate woody biofeedstock also suitable for cellulosic biofuel production. This work extends result that lowering overall lignin content, rather than altering S/G/H ratios, has the largest impact on reducing recalcitrance in eucalyptus.