Engineered Enzyme Degrades Biomass at Higher Temperature

Researchers at the Energy Biosciences Institute (EBI) have engineered an enzyme from a fungus that degrades lignocellulose biomass for biofuel production (e.g., grass and wood) so that the enzyme remains stable and active at a higher temperature range.

The EBI researchers used the strategy called "B factor guided mutagenesis" to enhance the thermal stability of an endoglucanase enzyme from the fungus Trichoderma reesei. The native form of this enzyme is not stable at temperatures above 50 degrees Celsius. Under thermal stress, the amino acids in the enzyme easily fall out of place just like loose knots in a rope. Researchers use the B factor value to measure the amino acid's ability to loosen. The researchers sought to tighten up some portions of the enzyme by mutating the amino acids and decreasing the B factor values. 

The engineered enzyme was up to twice as active on target substrates as the native enzymes at temperatures ranging from 50 to 65 degrees Celsius. When expressed in model fungus Neurospora crassa, it was able to degrade lignocellulose at 60 degrees Celsius as efficiently as the native enzyme at 50 degrees Celsius.

Enzymatic degradation of lignocellulose at high temperatures offers several potential advantages, including higher solid loadings due to reduced viscosity, lower risk of microbial contamination, greater compatibility with high temperature pretreatments, enhanced mass transfer and faster rates of hydrolysis.