(655c) In silico Metabolic Design of Two-Strain BioFilm Systems Predicts Enhanced Biomass Production and Biochemical Synthesis

Interacting microbial consortia are of keen interest for developing new biotechnological applications. While most efforts to engineer microbial consortia have focused on well-mixed, planktonic systems, naturally occurring microorganisms usually exist in multispecies biofilms encapsulated in self-produced extracellular polymer matrix. Numerous experimental studies have demonstrated the potential of engineered biofilm consortia. For example, we previously developed an artificial consortium comprised of two Escherichia coli strains engineered to interact to demonstrate enhanced nutrient utilization through syntrophic division of labor. The primary strain was glucose positive but could not grow solely on acetate, while the secondary strain was engineered to be an acetate specialist and was not able to catabolize glucose. When grown together in a biofilm, the interacting coculture demonstrated a 50-100% increase in cell productivity and created microenvironments containing either aerobic or anaerobic activity. Despite such advances, the parallel development of computational tools for in silico design and optimization of engineered biofilms has been lacking.

In this presentation, we demonstrate how metabolic modeling can be used for in silico design and optimization of biofilm systems for enhanced biomass and biochemical production compared to monoculture biofilms. The systems are comprised of a primary cell type that consumes the provided electron donor, glucose, and secretes acetate at inhibitory levels and a secondary cell type that scavenges the acetate as a carbon and energy source to support its growth, which has the benefit of also promoting primary cell type growth. Biofilms models are developed for two coculture systems: (1) glucose-positive E. coli as the primary cell type and a glucose-negative E. coli strain engineered for aerobic acetate utilization as the secondary cell type; and (2) a mutant E. coli strain engineered for aerobic isobutanol synthesis as the primary cell type and Geobacter metallireducens capable of anaerobic acetate utilization as the secondary cell type. The first system has been shown to form biofilms and is modeled to demonstrate enhanced biomass production with the shared terminal electron acceptor oxygen. The second system is designed to maximize isobutanol production using the partitioned terminal electron acceptors oxygen (E. coli) and Fe(III) (G. metallireducens). Our simulation results reveal several general principles for design of engineered biofilm communities, including the advantage of partitioned electron acceptors for enhanced acetate consumption.