Biological treatment of colored wastewater by Streptomyces fulvissimus CKS 7.

This study aims to investigate the biological processes related to the biodegradable potential of growing microbial cells for contaminated water treatment. Thus, the use of the Streptomyces fulvissimus CKS 7 (CKS7) has been evaluated for decolorizing efficiency of a solution containing a cationic triphenylmethane dye, crystal violet. The color reduction was monitored by UV-Vis spectroscopic analysis, through changes in their absorption spectrum and comparing the results with those of the respective controls. It was found that the CKS7 performed well and reached up to 100% effectiveness. The required process parameters have been apparently mild and include the reaction temperature of 27-30 °C, 10% inoculum size, under shaking conditions, whereas the time course of decolorization had been concentration dependent. A possible mechanism for removing dye from the working medium was accomplished in two steps: the binding of the dye on the bacterial cell surface, in addition to the dye biodegradation by the bacterial intracellular enzymes. After one cycle of the complete dye removal, the adapted culture was successfully reused for the same purpose. The phytotoxicity analysis revealed that non-toxic compounds were present in decolorized medium, indicating that the CKS7 bacteria seem to be a promising application for contaminated water treatment.

A fluorescent nanoprobe for single bacterium tracking: functionalization of silver nanoparticles with tryptophan to probe the nanoparticle accumulation with single cell resolution.

The investigation of the interaction of silver nanoparticles and live bacteria cells is of particular importance for understanding and controlling their bactericidal properties. In this study, the process of internalization of silver nanoparticles in Escherichia coli cells was followed by means of synchrotron excitation deep ultraviolet (DUV) fluorescence imaging. Antimicrobial nanostructures that can absorb and emit light in the UV region were prepared by functionalization of silver nanoparticles with tryptophan amino acid and used as environmentally sensitive fluorescent probes. The nanostructures were characterized by morphological (TEM) and spectroscopic methods (UV-vis, FTIR, XPS, and photoluminescence). The TEM images and the analyses of the UV-vis spectra suggested that the addition of tryptophan led to the formation of hybrid nanostructures with pronounced eccentricity and larger sizes with respect to that of the initial silver nanoparticles. The DUV imaging showed that it was possible to distinguish the fluorescent signal pertaining to silver-tryptophan nanostructures from the autofluorescence of the bacteria. The spatial resolution of the fluorescence images was 154 nm which was sufficient to perform analyses of the accumulation of the nanostructures within a single bacterium. The DUV imaging results imply that the tryptophan-functionalized silver nanoparticles interact with cell membranes via insertion of the amino acid into the phospholipid bilayer and enter the cells.

Dissipation of pirimiphos-methyl during wheat fermentation by Lactobacillus plantarum.

In this study, the dissipation of pirimiphos-methyl during wheat fermentation by Lactobacillus plantarum was investigated. Sample preparation for GC/MS detection of pirimiphos-methyl residues from fermented wheat substrate was carried out by two steps: extraction with 25 mL of methanol : acetone = 1 : 1 solvent mix for 30 min, followed by clean-up procedure through a glass column with florisil coupled with elution by 25 mL of ethyl acetate : acetone = 4 : 1. To obtain the highest pesticide degradation level, the fermentation conditions were optimized according to response surface methodology. Our results showed that L. plantarum was able to reduce the level of pirimiphos-methyl in wheat. Although pirimiphos-methyl was partially labile during sterilization prior inoculation (~37-50%), and there was also spontaneous chemical degradation of pesticide (~6-11%), overall L. plantarum enhanced degradation from 15 to 34%, that is, to nearly 81%. Additionally, the effect of pirimiphos-methyl on the lactobacilli growth, and efficiency of fermentation, was studied where pirimiphos-methyl inhibit the growth of bacteria in concentrations higher than 5 mg kg(-1), while the presence of pirimiphos-methyl did not overall affect the lactic acid fermentation.