With the EBI's latest methodology, the mechanisms by which cellulases trigger the hydrolysis of cellulose were delineated in three steps adsorption, complexation (molecular bonding) and reaction. The researchers discovered that the amount of surface area was critical for the activities of enzymes and for how well they work together in combination.
"The model explicitly tracks individual cellulases and key cellulose surface properties," the paper concludes. "Independent enzyme adsorption and complexation steps have been incorporated in an attempt to capture the most important details of the enzyme-substrate interaction. The model results illustrate the importance of understanding the effect of relevant surface areas to enzyme hydrolysis activity."
One phenomenon they tracked was the typical decline in the sugar breakdown rates after an initial "burst" phase, a reaction that usually leads to longer processing and greater enzyme loads, a costly and time-consuming step. Their research revealed a mix of surface area, structural changes within the surface, and cellulase interactivity during hydrolysis as major contributors to the slowdown. Further refinement of the model in future investigations should uncover more details.
"This work confirms that despite the complexity, enzymatic hydrolysis of cellulose is amenable to modeling," said Clark, the principal investigator for the EBI program on "Bioprocess Optimization from Cellulose Hydrolysis to Product Fermentation." "It also shows the importance of surface area, which we can control through pre-treatment (of the cellulose). There are now a lot of levers we can play with in finding an optimal enzymatic route to break cellulose down into sugars that can be converted to fuels."
Though many unknowns still remain in deciphering the complicated process that extracts sugars from plant cellulose, the EBI'
|Contact: Ron Kolb|
University of California - Berkeley