Evaluation of extracellular electron transfer in Pseudomonas aeruginosa by co-expression of intermediate genes in NAD synthetase production pathway

Simultaneous microbial electrochemical degradation of methyl orange and bioelectricity generation using coculture as anode inoculum in a microbial fuel cell

Methyl Orange, an azo dye, is a widely used colouring agent in the textile industry. The study aimed to investigate the efficiency of bioremediating bacteria in degrading methyl orange. Escherichia coli (E. coli), a Methyl Orange-degrading bacterium, was isolated from cow dung and its biochemical properties were analysed using 16S rRNA sequencing, and MALDI-TOF MS. A pre-cultured strain of Pseudomonas aeruginosa was co-cultured with E. coli in 1:1 ration in a microbial fuel cell (MFC) for simultaneous electricity production and methyl orange degradation. The degradation was combined with biological wastewater treatment at varying Methyl Orange concentrations, and the electrochemical characteristics were analysed through polarisation study, cyclic voltammetry, and electrochemical impedance spectroscopy. The impact of parameters such as anolyte pH, dye concentration, incubation time, and substrate concentrations were also studied. This study confirmed E. coli as an effective methyl orange degrading bacteria with a maximum % degradation efficiency of 98% after 48 h incubation at pH 7.0. The co-culture of isolated microorganisms at 250 mg/L of methyl orange concentration showed a maximum power density 6.5 W/m3. Further, anode modification with Fe2O3 nanoparticles on the anode surface enhanced power production to 11.2 W/m3, an increase of 4.7 W/m3.

Enhanced depolluting capabilities of microbial bioelectrochemical systems by synthetic biology

Microbial bioelectrochemical system (BES) is a promising sustainable technology for the electrical energy recovery and the treatment of recalcitrant and toxic pollutants. In microbial BESs, the conversion of harmful pollutants into harmless products can be catalyzed by microorganisms at the anode (Type I BES), chemical catalysts at the cathode (Type II BES) or microorganisms at the cathode (Type III BES). The application of synthetic biology in microbial BES can improve its pollutant removing capability. Synthetic biology techniques can promote EET kinetics, which is helpful for microbial anodic electro-respiration, expediting pollutant removing not only at the anode but also at the cathode. They offer tools to promote biofilm development on the electrode, enabling more microorganisms residing on the electrode for subsequent catalytic reactions, and to overexpress the pollutant removing-related genes directly in microorganisms, contributing to the pollutant decomposition. In this work, based on the summarized aspects mentioned above, we describe the major synthetic biology strategies in designing and improving the pollutant removing capabilities of microbial BES. Lastly, we discuss challenges and perspectives for future studies in the area.

The two faces of pyocyanin - why and how to steer its production?

The ambiguous nature of pyocyanin was noted quite early after its discovery. This substance is a recognized Pseudomonas aeruginosa virulence factor that causes problems in cystic fibrosis, wound healing, and microbiologically induced corrosion. However, it can also be a potent chemical with potential use in a wide variety of technologies and applications, e.g. green energy production in microbial fuel cells, biocontrol in agriculture, therapy in medicine, or environmental protection. In this mini-review, we shortly describe the properties of pyocyanin, its role in the physiology of Pseudomonas and show the ever-growing interest in it. We also summarize the possible ways of modulating pyocyanin production. We underline different approaches of the researchers that aim either at lowering or increasing pyocyanin production by using different culturing methods, chemical additives, physical factors (e.g. electromagnetic field), or genetic engineering techniques. The review aims to present the ambiguous character of pyocyanin, underline its potential, and signalize the possible further research directions.