The Efficacy of Silver Nitrate (AgNO₃) as a Coating Agent to Protect Paper against High Deteriorating Microbes

This study focuses on the efficacy of silver nitrate (AgNO3) as a coating agent used to preserve papers against microbial deterioration. To this end, the in vitro cytotoxicity of AgNO3 was assessed against two normal cell lines, WI-38 and HFB-4, to detect a safe dose that can be used as a coating agent, which was 80 µg mL−1. Bacillus subtilis B3 and Penicillium chrysogenum F9 were selected as high deteriorating microbes, previously isolated from a historical manuscript dating back to 1677 A.-D. The microbial growth inhibition, color change, mechanical properties, and cellulosic fibers of untreated/treated papers were evaluated. The data showed the efficacy of AgNO3 to inhibit the growth of B. subtilis with a percentage of 100% after 7 days, while it inhibits the growth of P. chrysogenum with a percentage of 85.9 ± 1.1% after 21 days. The color and mechanical properties of treated paper in the presence/absence of microbial inoculation were slightly changed, although they changed greatly due to microbial growth in the absence of AgNO3. The EDX analysis confirmed the successful adsorption of Ag-ion on papers, with a weight percentage of 1.9%. The cellulosic fibers of untreated paper in the presence of microbial growth were highly deteriorated as compared with treated and standard filter paper (shown by FT-IR and SEM)