Electricity generation and real oily wastewater treatment by Pseudomonas citronellolis 620C in a microbial fuel cell: pyocyanin production as electron shuttle.

In the present study, the potential of Pseudomonas citronellolis 620C strain was evaluated, for the first time, to generate electricity in a standard, double chamber microbial fuel cell (MFC), with oily wastewater (OW) being the fuel at 43.625 mg/L initial chemical oxygen demand (COD). Both electrochemical and physicochemical results suggested that this P. citronellolis strain utilized efficiently the OW substrate and generated electricity in the MFC setup reaching 0.05 mW/m2 maximum power. COD removal was remarkable reaching 83.6 ± 0.1%, while qualitative and quantitative gas chromatography/mass spectrometry (GC/MS) analysis of the OW total petroleum and polycyclic aromatic hydrocarbons, and fatty acids revealed high degradation capacity. It was also determined that P. citronellolis 620C produced pyocyanin as electron shuttle in the anodic MFC chamber. To the authors' best knowledge, this is the first study showing (phenazine-based) pyocyanin production from a species other than P. aeruginosa and, also, the first time that P. citronellolis 620C has been shown to produce electricity in a MFC. The production of pyocyanin, in combination with the formation of biofilm in the MFC anode, as observed with scanning electron microscopy (SEM) analysis, makes this P. citronellolis strain an attractive and promising candidate for wider MFC applications.

Model Amphiphilic Polymer Conetworks in Water: Prediction of Their Ability for Oil Solubilization.

In this work, we computationally explored the ability of water-swollen, model ionizable ABA triblock copolymer-based amphiphilic polymer conetworks (APCNs) to solubilize a water-immiscible organic solvent (oil), via Gibbs free energy minimization. This was done as a function of the conetwork hydrophobe (A-blocks) mol fraction and the degree of ionization of the hydrophilic B-blocks. Expectedly, highest oil solubilization capacities were calculated for the most hydrophobic and least ionized APCNs, which could absorb up to 6.4 times more oil than water and exhibited a lamellar morphology. Our results also included a phase diagram, which indicated transitions from spheres to cylinders, lamellae, and unimers in oil, as the hydrophobe content increased and the degree of ionization decreased. All of these transitions were accompanied by discontinuous changes in the degrees of swelling in the aqueous and oil nanophases, discontinuous changes in the asymmetry ratios (for the anisotropic morphologies), and discontinuous changes in the oil solubilization capacities. This is the first time that a dual discontinuous volume phase transition is reported within a polymer gel.