*2.4. Preparation of the Cell-Free Supernatants of Endophytic Bacterium*

The cell-free supernatants (CFSs) of the selected endophytic bacterium were prepared according to [20], with slight modification. In brief, *Bacillus endophyticus* strain H3 was inoculated in NA liquid medium and incubated at 30 ◦C and 200 rpm for 2 days. The CFSs were purified by centrifugation of bacterial culture (approximately ~1 × 10<sup>8</sup> CFU/mL) at 10,000 rpm, at 4 ◦C for 20 min, and twice by using filter sterilization 0.22 µm. To rule out possible contamination, 100 µL of CFSs were spread on NA agar for one day. The CFSs were kept at 4 ◦C till their use in the biosynthesis of AgNPs.
