Protein‐Based Polymeric Metal–Nanocomposite Derived From Egg Albumin: A Highly Effective Antimicrobial Agent Against Bacteria

Abstract

ABSTRACTThe synthesis of four distinct protein‐based metal nanocomposites has been fabricated by employing egg albumin and zinc metal through a simple, straightforward two‐step method. The Fourier transform infrared (FTIR), X‐ray diffraction (XRD), and scanning electron microscopy (SEM) analyses confirmed the successful incorporation of zinc nanoparticles into the protein matrix and revealed an irregular microporous structure with average crystallite sizes of less than 100 nm. Thermal stability was assessed via thermogravimetric (TG) and derivative thermal gravimetry (DTG) analysis, revealing a notable increase in thermal stability in a high‐temperature range (300°C°C–700°C), suggesting remarkable stability at elevated temperatures. Antimicrobial efficacy against both gram‐positive (B. cereus and Lactobacillus spp.) and gram‐negative bacteria (E. coli and K. pneumoniae) was evaluated using paper disk diffusion, pour plate, and minimum inhibitory concentration (MIC) methods. All samples exhibited antibacterial efficacy, with zone of inhibition (ZOI) diameters ranging from 12 to 35 mm, and demonstrated a bactericidal effect by eliminating 93 to 98% of bacteria within 8 to 20 h at their MICs. Notably, protein–ZnO–PANI exhibited potent antimicrobial activity against all four bacterial strains and among all the samples, demonstrated higher antimicrobial activity than the unpolymerized nanocomposites. The disk diffusion study confirmed that a concentration of 25 μg/mL of protein–ZnO–PANI resulted in ZOI measurements of 25 mm and 35 mm, whereas MIC values of 300 μg/mL and 200 μg/mL were observed against Bacillus cereus and E. coli, respectively, and killed 95% of B. cereus and 98% of E. coli within 24 h. Based on the obtained results, a plausible mechanism was also proposed.