HLE Overview

HLE Overview

At Tethys Research we are developing novel enzymes (HLEs) for the pulp and papermaking industry that help separate the major components of woody biomass. This technology not only improves pulp yield, but also facilitates the separation and release of sugars. These sugars can then be made available for fermentation into biofuels and other basic chemicals. Tethys enzymes also improve sugar extraction from non-woody biomass. They are patent pending.

Today, petroleum is a predominant source for energy, as well as a starting point for the manufacture of many chemical products. As world consumption of oil has increased, so too has its economic, political and environmental costs. But there is another less-developed route to the production of fuels and platform chemicals ─ fermentation fed by the simple sugars contained in biomass.

Woody biomass, in particular, has many advantages over other forms of biomass as a raw material source. Trees require little or no cultivation, are sustainable, and their vertical growth means a high biomass yield per acre. Moreover, harvesting costs are low. Wood is also relatively inexpensive and is not connected to the human food supply unlike corn, whose use as a fermentation feedstock has sparked a heated food vs. fuel debate.

There are three major components of wood, yet only one, cellulose, is used to make paper. The second, lignin, has a significant energy content and is typically burned in mills to provide power. The third component, hemicellulose, a polymer of simple sugars, is frequently degraded in the pulp-making process and is usually burned with the lignin for a very nominal energy gain. However if separated out, hemicellulose can be depolymerized into its component sugars, which can then be fermented, using existing technology, into an array of “green” chemical products. Alternatively, the polymeric hemicellulose can be added to cellulose in the pulping process in order to increase pulp yields. Unfortunately, separating the hemicellulose from lignin and cellulose is a tough technical challenge.

Tethys is pioneering the development of hemicellulose:lignin etherases, or HLEs, a variety of enzymes that specifically and gently loosen the lignin away from hemicellulose without degradation. Tethys discovered the first member of this new class of enzymes, a mannan:lignin etherase (MLE). This enzyme specifically targets mannan, the major hemicellulose of softwoods. Tethys has also developed an XLE (xylan:lignin etherase), a HLE directed at the predominant hemicellulose of hardwoods and agricultural crops. Both enzymes are patent pending.

Together, the new enzymes promise to revolutionize the pulp-making process. For the first time, hemicellulose (25-40% of the total mass of trees) from the US annual harvest of approximately 1 billion softwood and hardwood trees, would be made available to increase pulp mill yields or for conversion by biorefineries into an array of fine chemicals and energy products, including ethanol.

Tethys is now in the process of discovering and developing enzymes that separate a different type of lignin bond from hemicellulose. These enzymes, as yet unnamed, target a different lignin attachment point to hemicellulose.


The value proposition offered by this technology is four-fold: (i) a significant increase in revenues by increasing cellulose yields for pulp; (ii) the generation of a valuable byproduct (hemicellulose) for use as a new sustainable chemical feedstock; (iii) a decrease in environmental footprint by reducing the amount of polluting chemicals used to delignify pulp; and (iv) a reduction in energy usage by decreasing the severity of the existing process(es), enabling any excess energy generated by burning lignin to be sold back to the power grid.


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