Pseudomonas aeruginosa metabolizes pyocyanin, a redox molecule related to diverse biological activities. Culture conditions for the production of pyocyanin in a defined medium were optimized using a statistical design and response surface methodology. The obtained conditions were replicated using as substrate an alkaline residual liquid of cooked maize and its by-products. The untreated effluent (raw nejayote, RN) was processed to obtain a fraction without insoluble solids (clarified fraction, CL), then separated by a 30 kDa membrane where two fractions, namely, retentate (RE) and filtered (FI), were obtained. Optimal conditions in the defined medium were 29.6 °C, 223.7 rpm and pH = 6.92, which produced 2.21 μg mL⁻¹ of pyocyanin, and by using the wastewater, it was possible to obtain 3.25 μg mL⁻¹ of pyocyanin in the retentate fraction at 40 h. The retentate fraction presented the highest concentration of total solids related to the maximum concentration of pyocyanin (PYO) obtained. The pyocyanin redox behavior was analyzed using electrochemical techniques. In this way, valorization of lime-cooked maize wastewater (nejayote) used as a substrate was demonstrated in the production of a value-added compound, such as pyocyanin, a redox metabolite of Pseudomonas aeruginosa NEJ01R.

Los subproductos de la producción de biodiesel, como el glicerol crudo, requieren opciones para su valorización, que permitan obtener productos de alto valor con aplicación en diversas áreas. A partir de esto, se analizó el uso del glicerol crudo para la producción de piocianina utilizando tres cepas de Pseudomonas aeruginosa, con el objetivo de aumentar la concentración obtenida de este metabolito y compararla con la producida usando caldo de lisogenia (medio LB). El efecto fue dependiente de la cepa usada, mostrado de manera positiva solo por dos cepas. Se analizó la fisiología de P. aeruginosa usando al glicerol como única fuente de carbono y del sustrato completo para la biosíntesis de piocianina. El compuesto extraído fue identificado por UPLC-MS y caracterizado por técnicas electroquímicas. La respuesta voltamperométrica de piocianina permitió analizar su capacidad para asistir procesos redox y los mecanismos en la superficie del electrodo, que podrían estar asociados a procesos de adsorción. Este estudio muestra el potencial de las cepas usadas para la obtención de metabolitos redox con aplicación en sistemas bioelectroquímicos; además, se planteó la alternativa para producir tales metabolitos usando subproductos de bioprocesos para la generación de energéticos, de amplio uso internacional.

In this work, zinc/silver particle (Zn/AgP) composite coatings were manufactured by electrodeposition to investigate their antibacterial capacity and corrosion rate in physiological environments. The morphology and composition of the coatings were analysed by glow-discharge optical emission spectroscopy and scanning electron microscopy coupled to an energy dispersive spectrometer. The results showed the formation of Zn/AgP composite coatings with a homogeneous distribution of Ag throughout the coating surface and depth. Additionally, the Ag content in the coatings increased with increasing concentrations of AgP in the electrolytic solution. The Zn/AgP composite coatings with 0.30 wt.% Ag on the surface (0.30 wt.% Ag_surf) showed efficiencies close to 100% growth inhibition of the bacteria Pseudomonas aeruginosa after 10 min of contact. The corrosion rate of the Zn and the Zn/AgP (0.30 wt.% Ag_surf) coatings in Hank’s, Ringer’s and Phosphate buffered saline (PBS) solutions was evaluated by polarization curves and by immersion tests over different time periods (7, 30, and 40 days). The corrosion rate of the Zn/AgP (0.30 wt.% Ag_surf) coatings was on the order of tenths of microns per year and the amount of zinc mass dissolving per day was in the range of 0.15 to 0.7 mg cm⁻². Additionally, the surface of the coatings was analysed by X-ray diffraction (XRD) after 40 days of immersion. These results showed the formation of ZnO, as the main corrosion product, in the samples immersed in Hank’s and Ringer’s solutions. In the samples immersed in PBS, the formation of a passivating film of Zn₂(PO₄)₃·2H₂O was detected.