STUDY ON THE APPLICATION OF WHEAT FLOUR RESIDUE IN THE FERMENTATION OF Acinetobacter nosocomialis CYS-V3 FOR BIOSYNTHESIS OF SILVER NANOPARTICLES AND EVALUATION OF THEIR POTENTIAL AGAINST ROOT - KNOT NEMATODES ON BLACK PEPPER

Abstract

The bacterial strain Acinetobacter nosocomialis CYS-V3 has the potential for extracellular biosynthesis of silver nanoparticles (AgNPs) with potential inhibitory,  nematicidal and fungicidal activity against Meloidogyne spp. and Phytophthora spp. fungi that are harmful to black pepper (Piper nigrum) plants. Biogenic AgNPs offer a safe and environmentally friendly alternative to chemical pesticides. To date, the application of wheat flour residue for culturing A. nosocomialis CYS-V3 in AgNPs production via fermentation remains limited. Most existing studies have employed commercial nutrient media as carbon/nitrogen sources for the fermentation process. Aiming to reduce production costs and generate environmentally benign products, cassava starch processing byproduct (CSPB) was utilized as the primary substrate for fermenting A. nosocomialis CYS-V3. The results showed that after 72 hours of cultivation under CT4 and CT5 conditions (corresponding to 70% and 100% CSPB, respectively), bacterial densities reached 3.1 x 10⁸ CFU/mL and 2.7 x 10⁸ CFU/mL. The fermented supernatant of A. nosocomialis CYS-V3 was subsequently used for the biosynthesis of silver nanoparticles. Characterization of the nanoparticles indicated that the AgNPs were spherical in shape, exhibited an absorption spectrum within the range of 420 - 540 nm with a maximum peak at 400 nm, had a small particle size (86.5 nm), and demonstrated high stability with a zeta potential of -48.3 mV. The biosynthesized AgNPs in this study exhibited strong inhibitory efficacy (100%) against nematode egg hatching after 3 days of incubation, and second-stage juvenile nematodes at a concentration of 1.25 ppm AgNPs after 5 days of incubation.