Quorum sensing-driven riboflavin-hyperproducing electroactive bacteria for enhanced bioelectricity generation from sludge: From modular optimization to process performance
Waste activated sludge (WAS) represents a significant byproduct of wastewater treatment and a renewable resource for bioenergy. Bioelectrochemical systems (BESs), which couple microbial metabolism with electrochemical processes, can directly convert the organic matter in WAS into electricity. However, their performance is often constrained by the limited extracellular electron transfer (EET) capacity of electroactive bacteria. To overcome this constraint, we designed a quorum sensing-driven synthetic strategy to create self-regulated, riboflavin-hyperproducing Shewanella oneidensis. By engineering an Esa quorum-sensing circuit to autonomously control riboflavin biosynthesis, coupled with promoter tuning and codon optimization, we developed the strain SQR2, which produced 269.9 mg/L riboflavin under bioreactor conditions without impairing bacterial growth. The enhanced riboflavin production substantially improved BES performance, increasing the current density and power output by 22.2- and 11.6-fold over the control, respectively. In hybrid BESs treating WAS, the introduction of the SQR2 strain further promoted electricity generation, reduced charge-transfer resistance, and selectively enhanced electroactive microbial taxa. Our study demonstrates a scalable, inducer-free strategy—from genetic design to process application—that strengthens sludge-based bioelectricity generation and supports sustainable wastewater resource recovery.