Deciphering the synergistic mechanism of quorum sensing and sulfate-reducing bacteria for directed acetate conversion during sludge fermentation.

Insights into the suppression of filamentous bulking by quorum quenching in the activated sludge process with low dissolved oxygen: Endogenous quorum quenching mediated multi-enzymatic degradation of AHLs and carbon-flux redistribution.

Under low-DO operation, the SBR supplemented with P-gel effectively suppressed sludge bulking, prevented biomass loss, and sustained stable nutrients removal by regulating physicochemical properties of activated sludge.

Cultivation-dependent effects of quorum sensing signals on a lactic acid and chain-elongating bacterium

In situ fermentation-coupled symbiosis of polyphosphate-accumulating organisms and microalgae for efficient nutrient removal and sludge reduction in low carbon-to-nitrogen ratios wastewater.

Microalgae-bacteria consortia (MBC) integrated with polyphosphate-accumulating organisms (PAOs) treat wastewater sustainably, but face excess sludge and light-dark mismatch issues. This study developed in situ fermentation-coupled photo simultaneous nitrification-denitrification phosphorus removal (F/P-SNDPR) systems by incorporating fermentative PAOs into MBC for low carbon-to-nitrogen ratios (C/N) wastewater. The effects of light-dark cycles on nutrient removal, sludge fermentation, and microbial dynamics were investigated. Under an optimal 16 h dark/8h light cycle, the F/P-SNDPR system achieved > 83% nitrogen and > 95% phosphorus removal, with low sludge production (312.21 mgVSS/d) and low net CO2 emissions. Prolonged light and dark phases promoted early microbial apoptosis and subsequent cell lysis, respectively, thereby facilitating fermentation. Combined dark duration and photoinhibition suppress nitrite-oxidizing bacteria, enabling stable partial nitrification. Flow cytometry and metagenomic results identified Candidatus Phosphoribacter as the primary fermentative microorganism. Its fermentation-associated genes, including LivFGHMK and Pta, facilitated volatile fatty acid (VFA) production during the dark phase. The generated VFA supported Candidatus Accumulibacter/Candidatus Competibacter to enhance nutrient removal, driven by key functional genes for polyphosphate metabolism (Ppk and Ppx) and denitrification (NirS, NirK, and NosZ). Overall, The F/P-SNDPR system offers a low-carbon strategy for efficient low C/N wastewater treatment without mechanical aeration or external carbon addition, while reducing sludge production.

Suppression of quorum sensing-mediated cell autolysis for highly efficient lactic acid production by Lactobacillus paracasei LYS2.

Lactic acid (LA) is an important platform chemical with diverse applications and growing market demand. Microbial fermentation using Lactobacillus paracasei is a major route for LA production. However, L. paracasei fermentation often suffers from decreased cell biomass and viability due to cell autolysis, limiting LA production. Quorum sensing (QS) mediates bacterial communication and population behavior, but its role in regulating cell autolysis during LA fermentation remains unclear. In this study, QS inhibition in L. paracasei LYS2 is shown to alleviate cell autolysis, increases biomass, and enhances LA production. The underlying molecular mechanism of QS-mediated regulation was also explored. This fermentation strategy is applicable to the strain using sweet sorghum juice to replace glucose as the carbon source, achieving 206.1 g/L of LA, the highest reported from this substrate to date. This work provides a promising strategy for LA production.

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.

Indole inhibits anaerobic digestion by disrupting AHLs-mediated quorum sensing.