Engineering Endoglucanase Enzymes for Higher Thermostability
Endoglucanase enzyme complexes break down the internal structure of cellulose, disrupting its crystalline structure and leading to glucose, the desired end product needed for fermentation to ethanol. Like all enzymes, endoglucanases only function within a certain temperature range; however, high temperatures are often part of the biomass breakdown process. Research at DOE’s Bioenergy Research Center (BESC) at Oak Ridge is pushing the upper boundary of the temperature range for endoglucanases from the microbe Clostridium phytofermentans. Percival Zhang and colleagues studied directed mutational evolution of mutant proteins from the endoglucanase Cel5A family. They found mutants that are actually more active at 60°C, with the exact activity dependant on the specific cellulose substrate used. These results suggest that there may be a more complex relationship between endoglucanase activity and soluble or solid cellulose substrates then was previously thought. Further research will seek additional improvements of endogluconases for potential application to biofuel production.
W. Liu, et al., “Engineering of Clostridium phytofermentans Endoglucanase Cel5A for Improved Thermostability,” Appl. Environ. Microbiol. 76, 4914-4917 (2010).