Bacteriocin-Nanoconjugates (Bac10307-AgNPs) Biosynthesized from Lactobacillus acidophilus-Derived Bacteriocins Exhibit Enhanced and Promising Biological Activities

Abstract

The proteinaceous compounds produced by lactic acid bacteria are called bacteriocins and have a wide variety of bioactive properties. However, bacteriocin’s commercial availability is limited due to short stability periods and low yields. Therefore, the objective of this study was to synthesize bacteriocin-derived silver nanoparticles (Bac10307-AgNPs) extracted from Lactobacillus acidophilus (L. acidophilus), which may have the potential to increase the bioactivity of bacteriocins and overcome the hurdles. It was found that extracted and purified Bac10307 had a broad range of stability for both temperature (20–100 °C) and pH (3–12). Further, based on Sodium dodecyl-sulfate polyacrylamide gel electrophoresis (SDS–PAGE) analysis, its molecular weight was estimated to be 4.2 kDa. The synthesized Bac10307-AgNPs showed a peak of surface plasmon resonance at 430 nm λmax. Fourier transform infrared (FTIR) confirmed the presence of biological moieties, and transmission electron microscopy (TEM) coupled with Energy dispersive X-Ray (EDX) confirmed that AgNPs were spherical and irregularly shaped, with a size range of 9–20 nm. As a result, the Bac10307-AgNPs displayed very strong antibacterial activity with MIC values as low as 8 µg/mL for Staphylococcus aureus (S. aureus) and Pseudomonas aeruginosa (P. aeruginosa), when compared to Bac10307 alone. In addition, Bac10307-AgNPs demonstrated promising in vitro antioxidant activity against 2,2-diphenyl-1-picrylhydrazyl (DPPH) (IC50 = 116.04 µg/mL) and in vitro cytotoxicity against human liver cancer cells (HepG2) (IC50 = 135.63 µg/mL), more than Bac10307 alone (IC50 = 139.82 µg/mL against DPPH and 158.20 µg/mL against HepG2). Furthermore, a protein–protein molecular docking simulation study of bacteriocins with target proteins of different biological functions was also carried out in order to ascertain the interactions between bacteriocins and target proteins.

Antagonistic Interactions of Lactic Acid Bacteria from Human Oral Microbiome against Streptococcus mutans and Candida albicans

“…The competitive exclusion of pathogens due to the physical presence of LAB and enhancing the barrier function of the mucosal tissue are essential aspects of maintaining homeostasis [ 21 ]. The production of antimicrobial metabolites, including organic acids, exopolysaccharides, bacteriocins and anti-adherence biosurfactants, possess antimicrobial properties [ 22 , 23 , 24 ]. Therefore, studying the direct antimicrobial interactions of probiotic LAB with oral pathogenic microorganisms is essential.…”