NREL discovers new cellulose digestion mechanism necessary for biofuels industry

The National Renewable Energy Laboratory's (NREL) researchers have discovered a new mechanism that digests cellulose faster than enzymes from commercial preparations, and could prove to be a valuable mechanism for the biofuels industry.

The thermophilic bacterium Caldicellulosiruptor bescii uses an intermediate strategy, secreting many free cellulases that contain multiple catalytic domains; and one of these, CelA, includes a glycoside hydrolase family 9 and a family 48 catalytic domain separated by linker peptides, and three type III cellulose-binding modules.
"We are learning a lot about the evolution of these cellulases, how they can thrive in extreme environments, and how they operate on biomass."

Scientists at the US Department of Energy's (DOE) NREL have conducted a test on CelA and revealed that it produced more sugars, outperforming the most abundant cellulase in the commercial mixtures (Cel7A) when converting Avicel, a common cellulose standard.

When converting Avicel at its optimal temperature of 50°C, Cel7A has achieved only 50% of the performance of CelA, the NREL said.



Funded by the BioEnergy Science Center, the research work/enzyme will help cut costs of lignocellulosic fuels, from ethanol to other biofuels, should it continue to yield positive results in larger tests, NREL researchers claim.

The CelA exploits the common surface ablation mechanism driven by general cellulase processivity and excavates extensive cavities into the surface of the substrate, enabling greater synergy with more conventional cellulases and that will result in higher sugar release.

According to NREL scientists, CelA will also lower the levels of enzymes specialised in removing xylose in commercial cocktails and will reduce the cost of the enzyme cocktail, which is a major cost driver in the biomass into fuel conversion process.

NREL scientist Roman Brunecky said, "We are learning a lot about the evolution of these cellulases, how they can thrive in extreme environments, and how they operate on biomass."