Bacillus sp. VR Mediated Zinc Fortification in Microgreens in the Presence of Zinc Oxide Nanoparticles

Zinc deficiency associated malnutrition is a growing concern worldwide. The current study has been aimed to evaluate the zinc (Zn) biofortification in radish microgreen (RM) by using zinc solubilising bacteria (ZnSB) supplemented with the bulk zinc oxide (ZnO) or ZnO nanoparticles (ZnONPs). By the UV vis spectroscopic analysis, a major peak at 361 nm was observed for the selected ZnONPs. At the same time, Fourier transform infrared (FTIR) spectroscopy has identified characterestic absorption bands at 550, 1025, 2917.5, and 3555.7 cm⁻¹ for the same due to the Zn-O stretching vibrations. The transmission electron microscopy (TEM) analysis has also revealed the ZnONPs to have nano-spherical shape and by the Dynamic Light Scattering (DLS) analysis, its hydrodynamic size was found to be 151.94 nm. X-ray diffraction (XRD) patternat 32.38°, 35.16°, 37°, 48.33°, 57.38°, 63.5°, and 68.66° could further confirm the high crystallinity of ZnONPs used for the study. Further to this, the synergetic effect of Bacillus sp. VR, with ZnONPs was found to result in enhanced germination, and increased fresh biomass of microgreens by 90%. The ZnONPs and ZnSB treated microgreens were also found to have fourfold higher zinc content when compared with the bulk ZnO application. From the results of the study, seed nutrient priming mediated by the microorganisms could be demonstrated to be a feasible approach for enriching the radish microgreens (RM) with Zn. Here, the most effective Zn mobilisation was observed for the RM treated with the ZnSB followed by the ZnONPs application as evidenced through the changes in growth performance, yield, and zinc content.