Highlights Archive

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August 28, 2017

Net ethanol and acetate production from the wild type C. thermocellum strain (Cth_WT) and a m (...more)

Enchi Corporation Licenses Joint Dartmouth College and ORNL Technology
"Engineered microbe could potentially move the payback period for a commercial cellulosic ethanol operation from 15 years down to two years," Bill Brady, Enchi CEO.

August 01, 2017

Society for Industrial Microbiology and Biotechnology (SIMB) Awardees in BESC–2017
Brian H. Davison, Chief Scientist for Systems Biology and Biotechnology in the Bioscience Division at ORNL and the Science Coordinator in BESC, awarded SIMB Fellow 2017. Fellowship status is a special grade of membership in SIMB, acknowledging a career-long sustained record of significant research and/or service contributions to the profession of industrial microbiology and/or biotechnology.

Amanda Williams-Rhaesa, a fifth-year Ph.D. candidate in Biochemistry and Molecular Biology at the University of Georgia (Dr. Michael Adams' lab), received a 2017 SIMB Diversity Travel Award.

July 18, 2017

BESC glycosyl transferase work featured on cover

Mechanism of Fucosylation in Xyloglucan Biosynthesis revealed in Arabidopsis thaliana
FUT1 is a plant fucosyltransferase that carries out the final step in the synthesis of the hemicellulose xyloglucan, which is a major component of the plant cell wall and is involved in cell growth and expansion, energy metabolism, and signaling. X-ray crystallography revealed the structural architecture of FUT1 in complex with bound donor and acceptor substrate analogs, forming the basis for in silico studies that unraveled the mechanistic basis for fucosylation in GT37 enzymes. Structural and mutagenic analyses determined that there was no active site amino acid residue that could act as a base for catalyzing the reaction. In silico studies revealed the presence of a crucial water molecule that could conduct catalysis by shuttling the proton to enable a SN1-like mechanism.

July 14, 2017

Comprehensive Assessment of Glycosyl Residue Composition Analysis Methods
This is the first paper that provides side-by-side comparison of the efficacy of four different established methods in the analysis of glycosyl residue composition of cell walls from both primary wall-enriched leaf tissues and secondary wall-enriched wood/stem tissues of both dicot (Arabidopsis, Populus) and grass (rice, switchgrass) species.

July 11, 2017

2017 BESC Science Retreat
The Year 10 BESC Science Retreat was in Chattanooga, Tennessee from July 11-13, 2017 with 165 attendees from 13 BESC partner institutes.

July 05, 2017

adhA, nfnAB, and adhEG544D expression in C. thermocellum

Engineering T. saccharolyticum Ethanol Pathway into C. thermocellum Improves Biofuel Production
Clostridium thermocellum is a candidate for ethanol production from cellulose, but requires metabolic engineering to improve yield and titer. Thermoanaerobacterium saccharolyticum was previously engineered to produce ethanol at high yield and titer. Four of the genes that are responsible for ethanol production are adhA, nfnA/B, and adhEG544D. Introducing the T. saccharolyticum genes into C. thermocellum significantly increased ethanol yield.

July 03, 2017

Linking Overflow Metabolism and Growth Cessation in C. thermocellum
Findings of growth cessation and overflow metabolism provide metabolic engineering and fermentation strategies for high substrate loading fermentations to achieve high product yields.

June 19, 2017

Improving Bioavailability of Carbohydrate to C. bescii in Natural and Transgenic Switchgrasses
The bioavailability of carbohydrates to C. bescii was evaluated in the switchgrass lines unmodified Cave-in-Rock (CR), transgenic COMT-KD and Myb4-OE, and their corresponding parental lines. Each switchgrass line was examined as either hydrothermally treated (180ºC for 25 min) or untreated. C. bescii growth and carbohydrate solubilization (cellulose and hemicellulose) were determined for each treatment scheme (microbial, hydrothermal, or a combination of both). While C. bescii could significantly solubilize the transgenic switchgrass lines, including Cave-in-Rock, hydrothermal treatment was needed to solubilize 50% or more of the carbohydrate content.

May 01, 2017

Jonathan Mielenz, retired researcher from ORNL and BESC, was awarded the 2017 Charles D. Scott award (...more)

BRCs well represented at 39th Symposium on Biotechnology for Fuels and Chemicals
As part of the overall symposium the three DOE BRCs presented a combined total of twenty-two talks, including two as collaborations between the BRCs, and thirty-nine posters representing 28% of the talks and 15% of the posters. The presentations and posters highlighted the accomplishments, as well as common challenges in organization and research, in carrying out impactful mission-directed R&D in bioenergy.

May 01, 2017

Microbial hydrolysis changes poplar cell wall surfaces. Cellulose (yellow) decreases and lignin (blue or gray) becomes more prominent.

New Insights On Recalcitrance From Lignin Inhibition Of Microbial Deconstruction
Microbial solubilization of biomass selectively targets carbohydrates. Clostridium thermocellum, a highly effective cellulolytic microbe, can hydrolyze ~93% of 100gL-1 pure cellulose. The microbe solubilizes only partially hydrolyzes cellulose in untreated energy crops. Techniques used were quantitative fluorescence colocalization analysis and surface chemical imaging. Quantitative evidence for the cause of feedstock recalcitrance: depletion of surface carbohydrate increases lignin exposure which leads to inhibition of enzymatic activity, while the bulk residual biomass retains significant undigested sugar content. Limited hydrolysis is not caused by inhibitory hydrolyzed sugars nor fermentation products (i.e., ethanol).

April 17, 2017

Photos of the field experiments in the first (2013), second (2014), and third (2015) growing seasons (...more)

Multi-Year Study Of Transgenic Switchgrass Plants In Regulation Shows Improved Yield And Dependency On Expression Levels
Four promising lines with moderate or low microRNA (miR156) overexpression from prior greenhouse study were selected for a field experiment to assess miR156 expression levels and biomass yields over three years. The best performing line consistently produced more biomass (25-56%) than the control in all three seasons, which translated to the production of 30% more biofuel per plant in the final season. Transgenic plants with modifications to transcriptional regulators, which impact such a broad range of genes, will likely require more extensive field evaluations than those with single and simple trait gene modifications to evaluate the stability of the desired growth phenotypes.

April 12, 2017

CBP and Cotreatment

First-Of-A-Kind Study Of Thermophilic CBP With Cotreatment
Milling during lignocellulosic fermentation (or cotreatment) is an alternative to thermochemical pretreatment to enhance biological solubilization of lignocellulose. Carbohydrate solubilization was measured in consolidated bioprocessing with Clostridium thermocellum with cotreatment or with hydrothermal pretreatment. High carbohydrate solubilization was demonstrated without thermochemical pretreatment and added saccharolytic enzymes. C. thermocellum appears able to attack all the major linkages in cellulosic biomass provided that these linkages are accessible. The ability of C. thermocellum to withstand high intensity milling supports the feasibility of cotreatment. Less modified lignin may foster production of value-added coproducts.

March 27, 2017

Use of Caldicellulosiruptor saccharolyticus as a biological probe to report on changes in recalcitrance of plant biomass
C. saccharolyticus whole genome microarrays were used to access the transcriptome when grown on purified polysaccharides and chemically pretreated or genetically modified lignocellulosic substrates. Differential regulation of carbohydrate degradation, transport, and metabolism genes in C. saccharolyticus can be used to assess the availability of various plant polysaccharides to the microbe. This allows for inferences about the consequences of a chemical pretreatment or genetic modification of lignocellulose with an eye towards biofuels production.

March 21, 2017

Operating cost and revenue comparison

CBP-CT: an R&D-Driven Innovation with Potential for Disruptive Reductions in the Cost of Cellulosic Biofuels
Compared to current technology, the CBT-CT scenario was projected to offer 4.6-fold greater annual revenue, as well as 8-fold shorter payback period, and feasibility at ~10-fold smaller scale. CBT-CT is a potentially disruptive technology and a powerful, though still speculative, example of the potential benefits of including new-paradigm as well as in-paradigm innovation in R&D portfolios.

March 21, 2017

Improving Pretreatment Inhibitor Tolerance in Clostridium thermocellum
Bioconversion performance in the presence of common pretreatment inhibitors was improved through targeted strain engineering thus reducing barriers to achieving a robust consolidated bioprocessing strategy with Clostridium thermocellum.

March 18, 2017

Structure prediction and molecular recognition feature analysis of PdDUF266A.

Overexpression of DUF266 can significantly enhance both cellulose and biomass in Populus
(BESC's 900th publication)

Little is known about the function of Domain of Unknown Function 266 (DUF266)-containing proteins and no DUF266 protein has been characterized in Populus. A bioinformatics approach was taken to identify all DUF266 proteins in Populus and their relationship with their homologs in other species. A transgenic approach was used to determine the function of one member of DUF266 proteins in Populus (PdDUF266A). The resulting phenotypes make PdDUF266A a promising target for genetic manipulation for improving biomass quality.

March 10, 2017

Increasing delignification shows changes in morphology, elasticity, plasticity and adhesion

Use of Photoacoustic AFM to Spatially Resolve Nanomechanics of Plant Cell Wall Delignification
By chemically processing biomass and employing emerging nanometrology techniques, the various stages of lignin removal may be distinguished through the observation of morphochemical and nanomechanical variations. The cell wall nanomechanical properties undergo quantifiable reductions in plasticity, adhesion energy, and elasticity. These quantitative observations can be used to characterize delignification. The observed reduction in plasticity seems counterintuitive considering that lignin adds to cell wall rigidity.

February 27, 2017

Microbial Attachment to Cellulose Substrate Produces Widespread Gene Expression Changes
Unlike the majority of biofilm forming bacteria, C. thermocellum adheres to substrata that also provide its major carbon and energy sources. Before this study, discrete omics analyses of biofilm and planktonic cell populations had not been performed. Cellulolytic bacterial cells that evolved to thrive on solid carbon sources were shown to thoroughly alter expression of their central metabolism, anabolism, and homeostatic functions in response to the availability of solid attachment interfaces and solubilizable carbohydrates. The attached bacteria were functionally strong in growth and biomass conversion, while the planktonic cells were stressed and motile due to low available substrates.

February 07, 2017

Growth rate of C. thermocellum in response to various C5 sugars

Understanding the role of pentose sugars on C. thermocellum metabolism
This work highlights the importance of removing pentose sugars during bioconversion to biofuels, which could be achieved with C5 utilizing co-cultures or engineered strains of C. thermocellum, and is the first report of a functional ArgD-type cell signaling system in a thermophilic Firmicute and further work is warranted to understand the role of cell-to-cell signaling in achieving robust fermentations of lignocellulosic biomass.

January 20, 2017

SEM image of C. bescii (blue circles) attached to cellulose walls at 48 h

Visualization of Significant Alteration of Populus biomass by C. bescii
Caldicellulosiruptor bescii targets surface cellulose and hemicellulose, but increase of surface lignin could inhibit further sugar access. Biphasic cell growth is attributed to degradation of easily accessible sugars followed by utilization of more insoluble polysaccharides.

January 10, 2017

Metabolic Adaptation Of C. thermocellum To Growth Inhibitors Released During Deconstruction Of Switchgrass
Integrated omics data of microbial growth on complex lignocellulosic biomass over time provided a detailed view of the molecular machinery (metabolites and enzymes) that reveals temporal adaptation to a complex, lignocellulose substrate — information that is critical for engineering C. thermocellum's industrial efficacy.

January 03, 2017

Engineering N-terminal End of CelA Enhances the Cellulolytic Activity of Caldicellulosiruptor bescii
To test whether alteration of the N-terminal terminus of CelA GH9 and CelA GH48 domains might improve secretion and/or catalytic efficiency of CelA, repeating aspartate tags were introduced into the N-terminal ends of these 8 domains. Introduction of repeating aspartate tags resulted in an increase in the general activity of the exoproteome and a dramatic increase in growth of C. bescii on crystalline cellulose. Most efficient cellulase systems contain highly active exocellulase enzymes capable of decrystallizing cellulose, so the observed increase in activity on Avicel bears directly upon the ability of CelA to degrade realistic biomass feedstocks destined for biofuels production.

BioEnergy Science Center one of three DOE Bioenergy Research Centers established by the U.S. Department of Energy.