(727d) Engineering a Synthetic Fungal-Bacterial Consortium for Cellulosic Isobutanol Production

Present approaches to microbial cellulosic biofuel production are largely based on the “superbug” paradigm of aiming to incorporate all required functionalities (optimized biofuel production pathways, cellulase production, etc.) into a single organism. Inspired by the widespread occurrence of synergistic microbial communities in nature, we explore a novel alternative approach: the design and construction of a microbial consortium consisting of multiple species which cooperate to directly convert cellulose to biofuel. Three microbial specialists are utilized for the consortium: the cellulolytic fungus Trichoderma reesei RUT-C30, which secretes cellulase enzymes to hydrolyze lignocellulose into component hexose and pentose mono/oligosaccharides, an engineered E. coli hexose specialist that ferments hexose hydrolysis products, and an engineered E. coli pentose specialist that ferments pentose products.  The modularity of our system will allow it to be readily adapted to the large portfolio of existing E. coli strains metabolically engineered to produce biofuels or commodity chemicals.  As proof-of-concept, we demonstrate production of isobutanol from cellulosic feedstocks by implementing the consortium with isobutanol-producing E. coli strains.  Modeling and experimental studies are used to gain insights into the interplay between ecological interactions of the consortium members and isobutanol production.  Our results suggest strategies for optimizing robustness, stability, and isobutanol production by genetically tuning interactions between the consortium members.