Quorum sensing-driven riboflavin-hyperproducing electroactive bacteria for enhanced bioelectricity generation from sludge: From modular optimization to process performance

Cyanobacterial biorefinery: sustainable wastewater management for generation of biofuels and high-value products aligning with a circular economy approach

Fungal-microalgal symbiotic systems for wastewater bioremediation: metabolic integration, molecular mechanisms and industrial challenges

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

The restricted bioconversion of C3-C5 short-chain fatty acids (SCFAs) to acetate due to thermodynamic limitations is the main bottleneck during sludge fermentation. To alleviate this constraint, this study developed an optimized approach by integrating quorum sensing regulation with incomplete-oxidation sulfate-reducing bacteria (io-SRB) to improve the selective conversion of carbon towards acetate. The results revealed that the addition of 5 μM C8-HSL combined with io-SRB led to the highest SCFAs and acetate production at 141.9 mg COD/g VSS and 87.2 mg COD/g VSS at 5 d, which was 37% and 37% higher than the group without C8-HSL addition, while increase the C8-HSL dosage had no significant promotion of SCFAs production. C8-HSL effectively accelerated the efficient utilization of soluble carbohydrates and proteins during sludge fermentation, and functional group analysis further confirmed its promotional effect on the biotransformation of macromolecular organic matter throughout the fermentation process. Functional microbes, i.e., hydrolytic bacteria, acid-producing bacteria, and io-SRB (e.g., Desulfobulbus and Desulfovibrio), were enriched in the 5 μM C8-HSL system. The molecular ecological network and Mantel analysis revealed cooperative interactions among these functional microorganisms. Moreover, the synergistic effects of exogenous C8-HSL with io-SRB enhanced the expression of key functional genes involved in glycolysis, amino-acid metabolism, and acetate synthesis pathways. These findings may improve the understanding of the biological transformation mechanisms of sludge organic matter, and provide useful theoretical support for the efficient production of value-added products from sludge fermentation.

Modulation of catholyte ionic strength for enhanced bioelectricity generation and bioremediation of tannery wastewater in photosynthetic microbial fuel cells

Photosynthetic microbial fuel cells (PMFCs) represent an emerging class of bio-electrochemical systems capable of converting organic pollutants into electricity through microbial catalysis. Catholyte ionic strength is a principal determinant of PMFC performance, governing electrolyte conductivity, internal resistance, and microbial metabolic activity. To investigate this relationship systematically, four catholyte solutions were evaluated: ferric sulfate (Fe2(SO4)3), potassium permanganate (KMnO4), potassium dichromate (K2Cr2O7), and distilled water (DW). The constant anolyte comprising tannery wastewater, Spirulina A. platensis, and a bacterial inoculum was maintained across all configurations. Biological baseline controls using Spirulina, bacterial inoculum, and raw wastewater individually confirmed the synergistic contribution of the algal-bacterial consortium to electricity generation. The highest electrochemical performance was attained by MFC-5 under illuminated conditions with KMnO4 as the catholyte, producing an open-circuit voltage of 981.00 ± 1.00 mV, a power density of 233.81 ± 1.87 mW m−2, a coulombic efficiency of 81.92%, and a 51.60% reduction in biochemical oxygen demand. MFC-5 also achieved the highest removal of heavy metals, including chromium, cobalt, cadmium, copper, manganese, and iron, together with near-complete removal of bromide, nitrate, sulfate, and phosphate, reaching up to 99.97% for phosphate. X-ray diffraction and Fourier-transform infrared analyses of the recovered electrode deposits further identified quartz and silica, potassium–manganese oxide phases, and their reduction products, supporting the proposed pollutant removal mechanisms. These findings demonstrate how catholyte ionic strength governs PMFC performance and highlight the technology's promise for combined bioenergy recovery and sustainable industrial wastewater treatment.

Machine learning-assisted quorum sensing molecules regulate growth progression and bioactivity of an oxygenic photobiofilm for non-aeration greywater purification.

Microalgal-bacteria consortium provide self-aeration through photosynthetic oxygen production, offering an energy-efficient strategy for wastewater treatment. However, biofilm regulation in practical application is still limited by various factors, with acyl-homoserine lactones (AHLs) serving as key regulatory elements. This study established a microalgal-bacteria biofilm reactor (MBBfR) to investigate the regulatory mechanisms of AHLs-mediated quorum sensing under varying nitrogen (N) source. Results showed that a machine learning (ML) model successfully predicted the total suspended solids (TSS, R2 = 0.951), specific oxygen consumption rate (SOCR, R2 = 0.873) and oxygen generation rate (SOGR, R2 = 0.977) using extracellular polymeric substances (EPS) and AHLs as predictors. N source and C/N ratio altered AHLs concentrations and their associations with microbial community composition, with C6-HSL identified as the predominant AHLs. Nitrate facilitated the rapid formation of high quality and density biofilms, and enhanced signaling molecules secretion, thereby improving N removal efficiency. With high N stress and low C/N ratio, AHLs significantly induced EPS production, maintained microbial metabolic and photosynthetic activities, and promoted microalgal viability and proliferation. This signaling mechanism contributed to sustaining MBBfR stability and function. The findings provide a theoretical foundation and practical guidance for optimizing MBBfR-based wastewater treatment, enabling precise and convenient biofilm functionality regulation.

A Microalgal-bacterial Consortium Reshapes Biofilm Architecture to Enhance Stable Flux in a Gravity-Driven Membrane Bioreactor.

Global expansion of mariculture generates large volumes of saline wastewater that require sustainable and decentralized treatment to protect coastal ecosystems. Gravity-driven membrane bioreactors (GMBRs) are an attractive low-energy option for this purpose; however, severe membrane fouling in saline environments usually limits water flux. In this study, a microalgal-bacterial consortium (MBC) was introduced to reshape biofilm architecture and improve the long-term performance of GMBRs. Four ceramic membrane-integrated GMBRs were operated for 160 days to treat synthetic mariculture wastewater, including two MBC systems with bacteria-to-microalgae inoculation ratios of 3:2 and 5:2 and two bacteria-only controls. The optimized MBC system (5:2) achieved a stable flux of 14.9 LMH, which was 2.4 times that of the conventional GMBRs (∼6 LMH), while also showing superior nutrient removal (TN removal: 67.9-73.3%, effluent TN: 4.65-5.73 mg/L; TP removal: 92.0-96.3%, effluent TP: 0.1-0.3 mg/L). The improved performance was associated with the formation of larger, more porous aggregates (>20 μm), the development of a synergistic MBC architecture, and enhanced degradation of extracellular polymeric substances. Confocal laser scanning microscopy and scanning electron microscopy revealed a dynamic "loose-dense-loose" structural evolution of the biofilm in the MBC systems, which prevented the dense and irreversible layering observed in the conventional systems. Microbial community analysis further showed that the optimized system enriched functional bacteria (e.g., Nitrosomonas and Nitrospira) while maintaining high microalgal viability. These findings demonstrate that MBC is an effective strategy for improving GMBR performance and offers a sustainable approach for mariculture wastewater treatment.