PROJECT: BIOFUELS

Enzymatic Degredation of Cellulose

The ever increasing worldwide demands for energy, along with uncertain petroleum sources and the possibility of global climate change, has dictated the necessity for our nation to develop a sustainable and renewable alternative to fossil transportation fuel. Biofuels derived from lignocellulosic biomass are attractive alternatives due to the vast infrastructure already in place for the distribution of a liquid transportation fuel, and the fact that fuel derived from cellulose does not compete with human and livestock food resources. Furthermore, since cellulose is the most abundant renewable biopolymer on earth the feedstock for cellulosic biofuels is almost inexhaustible, and the utilization of cellulose for liquid fuel can achieve zero net carbon dioxide emission thereby making it a crucial component in our efforts to reduce green house gases.

Cellulosic biofuels are created by hydrolyzing cellulose to glucose and subsequently fermenting the glucose to make biofuel. Several major obstacles remain with regard to the viability of cellulosic biofuels including overcoming the natural resistance of cellulose to enzymatic depolymerization, known as biomass recalcitrance, which is primarily responsible for the high cost of cellulosic biofuels. To formulate ways to overcome biomass recalcitrance, a basic understanding of the substrate and enzymes involved in the hydrolysis of cellulose are needed. The enzymatic driven hydrolysis of crystalline cellulose to glucose is regulated by three different cellulases: endocellulase (EG), exocellulase (cellobiohydrolase, CBHI and CBHII), and β-glucosidase (BG).

The goal of my group’s proposed research is to model each of the three enzymes and evaluated their ability to bind substrate and catalyze the hydrolysis reaction. These simulations will utilize and develop novel methodologies so that the tools of statistical mechanics may be used to evaluate the underlying physics driving the enzyme substrate interactions and the catalytic reaction. These studies will provide insights into the enzyme systems and open new possibilities to engineering more efficient enzymes. Through collaborations with experimentalists and engineers these possible routes for enzyme improvement may be tested in vitro and subsequently implemented directly into test reactors (in vivo). The information gained from the in silico, in vitro, and in vivo experiments will then be used in the next generation bioreactors which will provide our nation with a renewable liquid transportation fuel alternative.

Non-Enzymatic Degredation of Cellulose

In addition to our focus on the enzymatic routes for degredation of cellulose the Maupin Group is also exploring non-enymatic methods for converting crystaline cellulose to glucose or other value added compounds/chemicals such as 5-hydroxymethylfurfurol. One of the benefits of utilizing a non-enzymatic method for processing cellulose is the ability to use high temperatures, which would denature enzymes. A promising alternative to enzymes is the use of ionic liquids as a 'green' solvent in which to solvate cellulose and conduct catalytic reactions. Ionic liquids possess several favorable properties including the ability to solvate/dissolve cellulose, no-vapor pressure, and the ability to fascilitate catalytic reactions with the addition of metal chlorides. Several research projects are currently underway with the goal of identifying the underlying physics that mediates ionic liquid dissolution of cellulose and fascilitates catalytic reactions such as with metal chlorides. The ultimate goal is the prediction/creation of novel task specific ionic liquids.