Solid-state fermentation for enhanced production of selenium nanoparticles by gamma-irradiated Monascus purpureus and their biological evaluation and photocatalytic activities.

Selenium nanoparticles (SeNPs) were successfully synthesized using the culture extract of Monascus purpureus ATCC16436 grown on sugarcane bagasse under solid-state fermentation. The rapid synthesis of SeNPs was completed after 30 min as confirmed by UV-Vis spectroscopy. Functional groups present in the synthesized SeNPs samples were confirmed by Fourier transform infrared spectroscopy. The synthesized SeNPs showed a single-phase crystalline structure. Transmission electron microscope revealed the spherical shape and the mean particle size was 46.58 nm. Dynamic light scattering analysis showed that the synthesized SeNPs were monodispersed and the recorded polydispersity index value was 0.205. Zeta potential value of - 24.01 mV indicated the high stability of SeNPs. Besides, the biological activities of antioxidant, anticancer and antimicrobial as well as the photocatalytic activities were also studied. SeNPs showed promising antioxidant activity with 50% inhibitory concentration of 85.92 µg mL^-1. Based on the MTT assay, SeNPs inhibited the proliferation of normal human melanocytes, human breast and liver cancer cell lines with 50% inhibitory concentrations of 45.21, 61.86 and 200.15 µg mL^-1, respectively. SeNPs showed broad spectrum of antimicrobial potential against the tested human and plant pathogens. SeNPs showed efficient degradation of methylene blue dye. Moreover, the effect of gamma irradiation on the production enhancement of SeNPs was also adopted. Exposure of the fungal spores to gamma rays at 1000 Gy increased the yield of SeNPs to approximately fivefold. Hence, this study suggests a new and alternate approach with the excellent biotechnological potentiality for the production of SeNPs.