Improved Conversion of Cellulose Waste to Ethanol Using a Dual Bioreactor System

Inedible plant materials such as grass and corn stover represent abundant renewable natural resources that can be transformed into biofuel. Although the enzymatic conversion of biomass to sugars represents an attractive means for this conversion, a number of problems have inhibited its use: the use of incomplete synergistic enzymes, end-product inhibition, and adsorption and loss of enzymes necessitating their use in large quantities. This project will develop a defined consortium of natural microorganisms that will efficiently breakdown biomass to energy-rich soluble sugars, and convert them to cleaner-burning ethanol fuel. In addition, a novel biocatalytic hybrid reactor system, dedicated to this bioprocess, will be developed. Phase I successfully identified and enriched a synergistic bacterial consortium capable of effectively degrading inedible plant fibers. A streamlined bioreactor system utilizing a newly developed nano-biocarrier with enhanced catalyst site density also was developed, and lignocellulose saccharification was accomplished with continuous removal of sugar. Phase II will involve the further optimization of cell growth conditions and a validation of the effectiveness of the nano-biocarriers in enzyme immobilization. Also in Phase II, the design of the bioreactor system will be modified to maximize sugar yield, a continuous fermentation process will be integrated into the system to convert sugars to ethanol, and a prototype reactor system will be developed. Commercial Applications and Other Benefits as described by the awardee: The technology should enable the development of alternative feedstock pathways for the production of biofuels and large-scale commodity chemicals. The global biofuel market was estimated at $15.7 billion in 2005, and is projected to grow by a factor of three by 2015.