Thermophilic Cellulases Compatible with Ionic Liquid Pretreatment

jbei

APPLICATIONS OF TECHNOLOGY:

Deconstruction of biomass for biofuels production
Paper recycling and pulp processing

ADVANTAGES:

Substantially improves the efficiency of saccharification of cellulose
Potential for consolidated pretreatment and saccharification of lignocellulosic biomass

ABSTRACT:

Researchers at the Joint BioEnergy Institute (JBEI) have identified thermophilic endoglucanases compatible with ionic liquid pretreatment for the saccharification of lignocellulose. The enzymes are used directly in a solution of ionic liquids and biomass to produce sugars from cellulose. They can solubilize the cellulosic sugars without the need to remove the ionic liquid first as well as when the cellulose is precipitated from the solution with antisolvents, such as water and ethanol. As a result, this technology opens up the possibility of consolidated pretreatment and saccharification of lignocellulosic biomass.

As shown in the figure below, the activity of the JBEI thermophilic cellulases is more stable than that of fungal cellulases in ionic liquid. (In the figure, JBEI Enzyme 1 is endoglucanase and JBEI Enzyme 2 is cellobiohydrolase). JBEI Enzyme 2 remains unchanged at 15% to 20% ionic liquid. Further, JBEI Enzyme 2 remains over 95% active in 15% ionic liquid, with an upper limit of 30% ionic liquid, for more than 20 hours. This represents a significant improvement over commercially available enzymes such as those from the fungus Trichoderma viride, which loses more than 50% of its specific activity in 2.9% ionic liquid and all of its activity in 10% ionic liquid. JBEI Enzyme 1 is also much more stable than the fungal enzyme, and the combination of the two enzymes is ideal for a synergistic hydrolysis of cellulose using an endoglucanase and a cellobiohydrolase. In addition, the JBEI enzymes have heat tolerances of up to 80ºC to 100ºC, compared with 50ºC for Trichoderma viride.

Currently, to increase enzyme accessibility, a combination of high temperature and extremes of pH are used during common pretreatment types such as dilute acid or ammonia fiber expansion. These approaches are incompatible with industrial enzymes used for hydrolysis, and they create byproducts that interfere with downstream hydrolysis and fuel production. Ionic liquids dissolve cellulose, which can then be separated out in an additional process. However, significant decreases in the available commercial fungal cellulase activity in the presence of trace amounts of ionic liquids necessitate extensive processing to remove residual ionic liquids from the recovered cellulose. By developing stable cellulases that are active in the presence of high amounts of ionic liquids, the additional processing step can be eliminated, thereby reducing cost and time.

EJIB-2666 is best considered in conjunction with JBEI invention EIO-2667, Thermophilic Endoglucanase Enzymes Engineered For Increased Activity, which increases the absolute activity of the endoglucanase from Thermotoga maritima.

STATUS: Published patent application # US2010/032320 available at www.wipo.int.