A closer look at the enzymes that deconstruct biomass

Novozymes’ Cellic™ enzyme products are designed to breakdown pretreated biomass into fermentable sugars.   CTec, designed for cellulose hydrolysis, is an enzyme “cocktail” — a mixture of several enzyme proteins. Why different types of enzymes, instead of just one type of enzyme for breaking down the biomass? The reason is that different classes of cellulases can exhibit synergy — that is, when combined together, the net performance of the enzyme mixture is greater than the predicted performance expected simply by summing up what each enzyme does to deconstruct biomass by itself.  Novozymes has taken advantage of enzyme synergies to create a more powerful mix of enzymes, which helps to bring down the cost of producing sugars from cellulose. 

Here are some of the major cellulase types found in CTec:

• Endoglucanases (EGs) – These are enzymes in the cocktail that break bonds between adjacent sugar molecules in a cellulose chain.  Thus, EGs fragment the cellulose chain into shorter lengths. 
• Cellobiohydrolases (CBHs) – These enzymes attack the ends of cellulose chains.  They “chew off” sugars from the cellulose ends, mainly releasing cellobiose, which is a soluble molecule, composed of two glucose molecules.  Because EGs create new “ends” for CBHs to act upon, these two classes interact synergistically.
• Beta-glucosidases (BGs) – This enzyme type breaks down very short sugar chains, such as the glucose dimer cellobiose, and releases glucose.  In addition to releasing a fermentable sugar, BGs are important because they decrease the amount of cellobiose.  The result is improved performance of the other enzymes in the mixture, because cellobiose is an especially potent inhibitor of cellulases.

In most cases, pretreated biomass feedstock contains at least some insoluble hemicellulose in addition to the insoluble cellulose.  Hemicellulose content varies depending on the type of pretreatment used, as well as the source of the plant material.  Hemicellulose can obstruct access to the cellulose, making it harder for the CTec enzymes to get to the cellulose chains.  To deal with this issue, Novozymes has a solution: HTec.  This product contains an enzyme that is especially effective at breaking down hemicellulose. Therefore, customers may see a boost in performance when including HTec in combination with CTec.

Source: Novozyme