High-Throughput Cellulase Evolution Against Pre-Treated Lignocellulosic Biomass

Replacing fossil fuels with cellulosic biofuels can greatly reduce carbon emissions and reduce our dependence of foreign energy sources. However, while cellulosic feedstocks are inexpensive, the production costs of cellulosic fuels are not low enough to be cost competitive with gasoline. One problem is that the enzymes currently used to deconstruct cellulose back to its constituent glucose molecules are simple to manufacture but fundamentally too inefficient. Moreover, cellulolytic enzymes have proven difficult to enhance in the laboratory, largely because most enhancement techniques have been demonstrated with soluble analogs of cellulose, which are wholly unlike the heterogeneous slurries derived from lignocellulosic biomass. This project will employ an ultra-high-throughput enzyme evolution system to improve the efficiency of cellulose-digesting enzymes against insoluble, pre-treated lignocellulosic biomass. The process will be able to screen billions of gene variants per day without the use of robotics. In Phase I, two complementary bacterial cellulases will be selected for their ability to hydrolyze pretreated biomass feedstock. Phase II will explore cellulases from high-expression fungal systems that are more suitable for industrial scale production. Commercial Applications and other Benefits as described by the awardee: The new enzymes should find use in the production of cellulosic biofuels or in any renewable chemical process that uses glucose as a starting material. The industrial enzyme market is expected to grow by 9% annually, and the cellulose market segment is still nascent. The technology would help the country transition to a low-carbon renewable liquid fuel source and provide a renaissance in agricultural technology and rural development, as degraded farmland is replanted with energy crops