Isolation of indigenous Glutathione producing Saccharomyces cerevisiae strains

BACKGROUND

Glutathione (GSH) is a non-protein thiol compound, which plays an important role in the response to oxidative stress and nutritional stress. The aim of this study was to isolate indigenous S. cerevisiae strains capable of effectively produce GSH.

METHODS

One hundred-twenty sweet fruit samples were collected. The strains were isolated on yeast glucose chloramphenicol (YGC) agar medium and identified. The isolates were evaluated for GSH producing on yeast malt (YM) medium. Concentration of glutathione was investigated by recording absorbance of all samples at wavelength 412 nm (Ellman's method). In addition, optimization of glucose and peptone concentration in culture medium and the effects of various environmental conditions such as temperature (20-35 °C), agitation rate (150-250 rpm), and initial pH (4.0-6.0) were assessed on producing of GSH.

RESULTS

From 120 samples, 80 isolates were identified by morphological, biochemical and molecular tests as S. cerevisiae. Five isolates were capable to produce effectively GSH. The optimal culture conditions were agitation rate, 200 rpm; temperature, 30 °C; initial pH, 6; glucose, 30 g/l; and peptone concentration, 5 g/l. In optimal conditions, the amount of derived glutathione was improved compared to YM basal medium and highest GSH concentration (296.8 mg/l) was obtained after cultivation with shaking for 72 h.

CONCLUSION

The possibility of obtaining S. cerevisiae cells with a high GSH intracellular content can be considered an interesting opportunity of furthering the range of application and utilization of this molecule.

Influence of plasmon destructive interferences on optical properties of gold planar quadrumers

Arrays of planar symmetric gold quadrumers consisting of a central nano-disc surrounded by three similar nano-discs belonging to the D(3h) point group were designed and fabricated. Since the geometrical configuration of quadrumers is the same as planar trigonal molecules, nano-discs can play the roles of artificial atoms to study the coupling trends among them. The plasmonic properties of the nano-disc structures are investigated by reflection spectrum measurement and finite-difference time-domain calculation with good agreement. Plasmon interaction among the nano-discs is also studied via a mass-spring coupled oscillator model. A pronounced Fano resonance (FR) is observed for the fabricated nano-discs with inter-disk gaps of around 18 nm during light irradiation at normal incidence. Although the obtained FR is independent of the excitation polarization, the near-field energy spatial distribution can be flexibly tuned by the polarization direction. This has potential applications in nano-lithography, optical switching and nonlinear spectroscopy.