(785c) Engineering Microbial Communities for Cellulose Degradation and Modular Production of Target Chemicals
Cellulosic biomass, an abundant biological waste material, can serve as an inexpensive carbon source for producing valuable products using microbial ecosystems. A critical step in developing a system dependent on waste is the degradation of cellulose into glucose monomers, which can be subsequently utilized for growth and product generation. Current approaches rely on the expensive production and purification of enzymes for this purpose, or harsh pretreatment processes. However, the use of a mixed community where the labor is divided between polymer degraders and target product makers has the potential to address this challenge. To this end, we are building a community of B. megaterium and E. coli for bioproduction from cellulose. We will describe our recent progress engineering the Gram-positive Bacillus strain for targeted cellulase secretion. Complete degradation of cellulose requires a combination of three cellulose functions â?? an endoglucanase, a cellobiohydrolase, and a beta-glucosidase. The goal of this work is to generate a system of one or more B. megaterium that secrete a combination of requisite cellulases, for synergistic degradation of cellulose in co-culture. We have tagged cellulases with a small library of signal peptides (SPs), found to trigger protein secretion in B. megaterium, and demonstrated our novel strategy leads to efficient expression and secretion. Cellulase activity against amorphous cellulose was further confirmed through a series of bioassays, validating that we have engineered strains with significant cellulase secretion and activity. We have also demonstrated that the glucose monomers released through the actions of the cellulases secreted by B. megaterium can be used to support both B. megaterium and E. coli growth in co-culture. We will describe our current efforts to explore the role of induction, expression and inoculation ratios on community composition and the production of target bioproducts by the E. coli maker cells.