A three-species microbial consortium for power generation

Design and construction of synthetic microbial consortia is a promising strategy to enhance the performance of bioelectrochemical systems (BESs) and to facilitate practical applications in bioenergy production. According to the design principle of "division-of-labor", we synthesized a three-species microbial consortium for power generation, consisting of engineered Escherichia coli, Bacillus subtilis and Shewanella oneidensis. In this consortium, E. coli digested glucose to produce lactate as a carbon source and an electron donor; B. subtilis produced riboflavin as an electron shuttle; and S. oneidensis served as the exoelectrogen to generate electricity. In return, S. oneidensis oxidized lactate to acetate, which fed E. coli and B. subtilis as the carbon source. Thus, the three species formed a cross-feeding microbial consortium, which performed "better together" for power generation. As a result, glucose (11 mM, total 0.28 g) was converted to electricity for more than 15 days with high energy conversion efficiency (up to 55.7%). The microbial composition and electricity output were stable throughout the operation cycle. Furthermore, the consortium exhibited highly functional robustness to fluctuations in the initial inoculation ratio of the three strains. This system provided new insight into the rational design of more efficient, stable, and robust synthetic microbial consortia applicable in bioenergy and environmental bioremediation.