Progress in understanding and overcoming biomass recalcitrance: a BioEnergy Science Center (BESC) perspective
Gilna et al. Biotechnol Biofuels
Progress in understanding and overcoming biomass recalcitrance: a BioEnergy Science Center (BESC) perspective
Paul Gilna 0 2 3
Lee R. Lynd 0 1 2
Debra Mohnen 0 2 5
Mark F. Davis 0 2 4
Brian H. Davison 0 2 3
0 Biosciences Division, Oak Ridge National Laboratory , 1 Bethel Valley Road, Bldg. 1505, Rm. 100A, Oak Ridge, TN 37831‐6037 , USA
1 Thayer School of Engineering, Dartmouth College , Hanover, NH 03755 , USA
2 Biosciences Division, Oak Ridge National Laboratory , 1 Bethel Valley Road, Bldg. 1505, Rm. 100A, Oak Ridge, TN 37831‐6037 , USA
3 BioEnergy Science Center, Oak Ridge National Laboratory , Oak Ridge, TN 37831 , USA
4 National Bioenergy Center, National Renewable Energy Laboratory , Golden, CO 80401 , USA
5 Complex Carbohydrate Research Center and Department of Biochemis‐ try and Molecular Biology, University of Georgia , Athens, GA 30602 , USA
The DOE BioEnergy Science Center has operated as a virtual center with multiple partners for a decade targeting overcoming biomass recalcitrance. BESC has redefined biomass recalcitrance from an observable phenotype to a better understood and manipulatable fundamental and operational property. These manipulations are the result of deeper biological understanding and can be combined with other advanced biotechnology improvements in biomass conversion to improve bioenergy processes and markets. This article provides an overview of key accomplishments in overcoming recalcitrance via better plants, better microbes, and better tools and combinations. A perspective on the aspects of successful center operation is presented.
Bioconversion; Bioenergy; Recalcitrance; Center operation; Biomass
Background
Biomass recalcitrance—the resistance of plants to release
their sugars for fermentation or upgrading—is a
primary barrier to efficient and economical production of
advanced biofuels [
1, 2
]. Overcoming and understanding
recalcitrance was the unifying vision of the US
Department of Energy (DOE) BioEnergy Science Center (BESC),
now in its final and 10th year of operation. The mission of
BESC was “to enable the emergence of a sustainable
cellulosic biofuels industry by leading advances in science and
science-based innovation resulting in removal of
recalcitrance as an economic barrier to cost-effective production
of biofuels [3].” Due to advances in biotechnology, BESC
believed that biological solutions were the most
promising path by which to achieve these breakthroughs. In
response to a DOE challenge [
4
], Oak Ridge National
Laboratory (ORNL) led the formation of BESC by
gathering experienced researchers from multiple US
institutions, who had been separately interested in separate
aspects of overcoming biomass recalcitrance targeting
advanced biofuels and specifically cellulosic ethanol.
Recalcitrance began as an operationally defined
phenotype. With both applied and fundamental goals, BESC
perceived that we needed to transform the understanding
of recalcitrance; this required detailed knowledge of the
chemical, structural, and physical properties of biomass
and how these properties influenced deconstruction by
enzymes and thermophilic microorganisms. This search
led to altering plant cell wall properties by manipulating
key plant polymer biosynthetic pathways, which led to
studies of the interactions of the plant cell walls and the
enzymes and microbes during deconstruction and
fermentation. The BESC team has redefined recalcitrance so
that now recalcitrance is on the path to being an
understandable and manipulatable set of properties based on
cell wall formation and bioconversion. A key outcome
of the BESC team’s approach was to transform
understanding in both fundamental and operational impacts to
strategies that will eliminate recalcitrance as an economic
barrier to commercialization.
This singular focus on recalcitrance science was
BESC’s hallmark worldwide. BESC was organized into
three areas: Biomass Formation and Modification,
Biomass Deconstruction and Conversion, and Enabling
Technologies (Fig. 1). All three areas included both
fundamental understanding and complementary
proof-ofconcept components. Our ability to design, conduct, and
analyze wide-ranging campaigns, along with our effective
communications and capacity to integrate
cross-disciplinary teams within the BESC organization, has been key
to our success in scientific areas that are critical to
overcoming the formidable biological and technological
barriers that biomass recalcitrance presents.
Discussion: major accomplishments to date
From late 2007 to fall 2017, BESC published more than
945 journal articles, 10% in high-profile journals (impact
factor > 9) and advanced the education of more than 230
professionals, who are now productive members of the
bioeconomy workforce. More details with respect to the
output of BESC and the other two USDOE Bioenergy
Research Centers are in Slater et al. [
5
].
Biomass formation
Populus and switchgrass (Panicum vir (...truncated)