Biomolecular Engineering Approaches to Enzyme Stability

To achieve high conversion yields of cellulose to glucose by the enzymatic route usually requires a good mix of cellulase enzymes including cellobiase. The stability of these enzymes functioning under operating conditions resembling industrial processes (high temperatures) is also an important parameter affecting glucose yields. Another environmental factor is the build up high concentrations of end-products (cellobiose and glucose) in the hydrolysate during the hydrolysis reaction as this too influences cellulase activity.

Altogether, these factors preclude cellulose being hydrolyzed linearly and completely over time, and this effect is important when considering cellulases functioning under optimal conditions to obtain high yields of glucose for commercial applications.

The BRI will attempt to address the problem related to enzyme instability by applying bioinformatics, computer-assisted molecular design (CAMD), and bioengineering techniques. Bioinformatics enables the analysis of natural diversity among biomass-degrading and ethanol-producing organisms for selection of microorganisms for industrial applications, and for identification of mutation points for molecular design. CAMD is a powerful tool for the re-design of proteins to better interact with the particular biomass of interest. The protein modifications suggested by CAMD are implemented through bioengineering of microorganisms. Hopefully this can lead to tailored "cellulases" with increased stability towards heat, and ultimately may also lessen the inhibitory effects caused by glucose. The same techniques can also be used for selection and/or molecular design of non-enzymatic proteins important for biomass conversion, such as sugar transporters and expansins. This approach will advance cellular and molecular research for the conversion of biomass to energy, chemicals, pharmaceuticals, and other high-valued bioproducts.