Powerful New Enzyme for Transforming Biomass
Converting plant cellulose and hemicellulose into fermentable sugars is a major bottleneck in the biofuel industry. Chemical pretreatment and enzyme hydrolysis (breakdown) usually are required. Among chemical pretreatments, ammonia fiber expansion (AFEX) alkaline pretreatment has many advantages. For example, it is a dry process and results in cleaved lignin-carbohydrate complexes without physical extraction. A variation on the process, called extractive AFEX, leads to the production of ‘cellulose III,’ an artificial form of cellulose that may be easier to break down. To be effective, these pretreatments must be paired with enzyme cocktails. As many as 18 different purified enzymes may be required for high yield conversion. Fewer enzymes would simplify biofuel production and lower costs. One approach is to swap out two or more single-function enzymes for a multifunctional enzyme.
UW–Madison researchers have engineered a multifunctional polypeptide capable of hydrolyzing cellulose, xylan and mannan. It is made of the catalytic core of Clostridium thermocellum Cthe_0797 (also called CelE), a linker region and a cellulose-specific carbohydrate binding module(CBM3). C. thermocellum is a well-known cellulose-degrading bacterium whose genome has been sequenced, annotated and published.
- Superior catalytic activity
- Less complex enzyme cocktails
- Biofuel production
- Hydrolyzing cellulosic materials including filter paper, crystalline cellulose allomorph I, amorphous cellulose, cellulose III and SIGMACELL
- May be used to improve animal fiber digestion
The new enzyme’s catalytic reactivity has been shown to be twice as high as native CelE.
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