The Biotransformation and Biodecolorization of Methylene Blue by Xenobiotic Bacterium Ralstonia pickettii

The biotransformation and biodecolorization of methylene blue (MB) dye using the bacterium Ralstonia pickettii was investigated. This experiment was conducted in a nutrient broth (NB) medium after adding MB at 100 mg L–1 concentration. Approximately 98.11% of MB was decolorized after 18 h of incubation. In addition, the metabolic products detected by LC-TOF/MS were Azure A (AA), thionine, leuco-MB, and glucose-MB, which indicated the MB degradation through a reductase that attacked the heterocyclic central chromophore group present in the structure. Moreover, azure A and thionine fragments resulted from the N-demethylase enzyme that attacked the auxochrome group. Thus, this research was assumed to be the first scientific report suggesting the potential to use R. pickettii in the biodecolorization and biotransformation of dye waste, particularly MB.

Electrochemical DNA Sensor Based on Poly(Azure A) Obtained from the Buffer Saturated with Chloroform

Electropolymerized redox polymers offer broad opportunities in detection of biospecific interactions of DNA. In this work, Azure A was electrochemically polymerized by multiple cycling of the potential in phosphate buffer saturated with chloroform and applied for discrimination of the DNA damage. The influence of organic solvent on electrochemical properties of the coating was quantified and conditions for implementation of DNA in the growing polymer film were assessed using cyclic voltammetry, quartz crystal microbalance, and electrochemical impedance spectroscopy. As shown, both chloroform and DNA affected the morphology of the polymer surface and electropolymerization efficiency. The electrochemical DNA sensor developed made it possible to distinguish native and thermally and chemically damaged DNA by changes in the charge transfer resistance and capacitance.