Lignocellulosic biomass is the most plentiful and sustainable resource on Earth, largely made up of plant residuals that would otherwise go unused and left to decay. Using this biomass as a source of alternative fuels can help offset the world’s dependence on fossil fuels. Scientists at the Energy Department’s National Renewable Energy Laboratory (NREL) have developed an enzyme that could change the economics of biofuel conversion by converting biomass to sugars up to 14 times faster and much cheaper than competing catalysts in enzyme cocktails today.
Using electron microscopy, NREL researchers and their partners at the University of Georgia found that the new enzyme, called CelA, not only ablates the cell wall of lignocellulosic biomass, it also excavates cavities into the surface. Other enzymes only ablate. CelA also worked faster on raw biomass than it did on biomass pre-treated with chemicals.
Biomass is composed of three types of polymers that are intermeshed to form plant cell walls: cellulose, xylan, and lignin. Each of the three polymers typically requires several types of enzymes to deconstruct them to soluble species that can then be upgraded to ethanol, drop-in fuels or chemicals. CelA is able to break down cellulose and xylan. Xylan, which wraps around the cellulose fiber, can contribute significantly to the manufacture of biofuels if its stubborn sugars can be released.
Even though CelA contains naturally occurring endoglucanase, the researchers found that adding more of the substance greatly accelerated the rate at which it broke down sugars.
CelA can also operate at much higher temperatures than other enzymes—80 degrees to 90 degrees Celcius—so it’s faster acting. Because it can operate above the boiling point of alcohol, the alcohol is separated naturally, saving a costly step in the conversion process.
If the enzyme continues to perform well in larger tests, it could help drive down the price of converting cellulose and, with it, the price of everything from jet fuel to ethanol, butanol, drop-in fuels and numerous chemicals.
In 2013, scientists from NREL, the University of Kentucky and the Universitites of Portsmouth and York in the UK published research about marine wood borer’s ability to use its own enzymes to break down biomass.