Biomass Pretreatment
NREL researchers are leaders in investigating and developing pretreatment technologies for hydrolyzing hemicellulose and solubilizing lignin in lignocellulosic biomass. This breaks the hemicellulose down into its component sugars and exposes the cellulose, so that it can be more easily broken down to its components. NREL biomass researchers have focused on a process model of dilute acid hydrolysis of hemicellulose followed by enzymatic hydrolysis of cellulose. They have, however, also investigated other pretreatment approaches and play a lead role in a research consortium effort to systematically evaluate all pretreatment technologies. For the dilute acid/enzyme model, NREL researchers have developed several innovative processing systems, greatly enhancing pretreatment effectiveness.
Cellulase Enzyme Development
NREL's research on enzyme development focuses on decreasing the cost of
the enzyme unit operation in the biomass saccharification process, which has been identified
as a key factor for developing cost-competitive biorefinery products. Researchers have
developed great expertise in the basic science underlying enzymatic hydrolysis. They are
working closely with major industrial enzyme producers to apply recombinant DNA technology
to bacteria and fungi to develop improved cellulase enzymes and to determine the most
efficient method for producing these enzymes.
Strain Development
NREL researchers are applying sophisticated metabolic engineering techniques to
develop microorganisms that can more effectively ferment the sugars in biomass. Lignocellulosic
biomass contains five carbon sugars such as xylose (from the hemicellulose) as well as the more
"common" six carbon sugars such as glucose found in grains. This makes fermentation and other
bioprocessing far more challenging. While some biorefinery scenarios will take advantage of the
different sugar streams to produce multiple products, others will be more cost effective if all
the sugars can coferment in a single set of equipment.
Researchers are developing microorganisms that can coferment all the sugars in
biomass in order to improve ethanol production economics. They are applying sophisticated metabolic
engineering techniques to Zymomonas mobilis that can coferment both xylose and arabinose along with
glucose. With industrial partners, researchers are working to develop designer strains for specific
feedstocks, feedstreams, and processes.
Bioprocess Integration, Scale-up, and Demonstration
A team of biotechnology researchers focuses on integrating all the unit operations
of biomass conversion. With extensive knowledge of the individual unit operations, these
researchers focus on linking unit operations together for industrial application and on
demonstrating integrated processes at the mini-pilot and pilot scales. They also conduct
rigorous bench-scale experimentation to improve specific unit operations within the process.
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