Fast-Degrading Enzyme Reveals Novel Cellulose Digestion Mechanism

Researchers at the National Renewable Energy Laboratory (NREL) of the U.S. Department of Energy have found that an enzyme produced by a bacterium that thrives in hot springs possesses remarkable catalytic properties which enable it to digest cellulose almost twice as fast as the leading commercial cellulase enzyme.

NREL researchers have tested and characterized the CelA enzyme secreted by Caldicellulosiruptor bescii, a bacterium first found in the Valley of Geysers on the Kamchatka Peninsula in Russia in 1990. They found that CelA produced more fermentable sugars than Cel7A, the most potent cellulase enzyme in leading commercial enzyme mixtures, under industry standard test for cellulose degradation. They found that CelA not only can digest cellulose, but it also creates cavities in the material, which leads to greater synergy with more conventional cellulases, resulting in higher sugar release.

The NREL researchers who reported their finding in the journal Science described CelA as "an amazingly complex enzyme", which combines two catalytic domains with three binding modules." The dual catalytic domains working in concert are most likely responsible for fast degradation of cellulose.

NREL scientists also found that CelA can attack xylose, which means that the amount of enzymes in commercial cocktails for removing xylose could be further lowered, translating to lower costs. The enzyme with its remarkable cellulose digesting mechanism promises to bring down the cost of making lignocellulosic biofuels or fuels made from hard-to-digest biomass sources.