Lactobacillus species mediated synthesis of silver nanoparticles and their antibacterial activity against opportunistic pathogens in vitro

Abstract

Introduction: Application of lactic acid bacteria for synthesis of silver (AG) nanoparticles (NPs) could be a good ecological friendly alternative to chemical and physical methods. The objective of this study was to investigate the biosynthesis of silver NPs using Lactobacillus strains and to compare their monosaccharide composition of capsular exopolysaccharides and the antibacterial activity of synthesized nanoparticles. Methods: The washed cells of 22 Lactobacillus strains were used for in vitro silver nanoparticle biosynthesis from silver nitrate solution. The NPs formation was confirmed by UV-visible spectroscopy and transmission electron microscopy (TEM) analysis. TEM micrographs were used for the evaluation of NPs size. The monosaccharide composition of capsular exopolysaccharides was determined using GC/MS analysis. The antimicrobial activity was determined by agar well diffusion assay. Results: The capsular layers of Lactobacillus strains contained heteropolysaccharides that were composed mostly of glucose, mannose, galactose and rhamnose in a different molar ratio. It was found that Ag NPs with large size (30.65 ± 5.81 nm) obtained from L. acidophilus 58p were more active against S. epidermidis, E. coli, K. pneumonia,S. flexneri and S. sonnei compared with Ag NPs from L. plantarum 92T (19.92 ± 3.4 nm). Conclusion: The size and antibacterial activities of Ag NPs were strain-dependent and such characteristics may be due to the capsular biopolymer composition of Lactobacillus strains used for Ag NPs synthesis.

Biosynthesis of silver nanoparticles mediated by culture filtrate of lactic acid bacteria, characterization and antifungal activity

“…The monosaccharide composition of capsular heteropolysaccharides from different Lactobacillus strains could explain the ability to reduce the silver ions and produce AgNPs with different sizes and size distribution. The differences in antibacterial activity of AgNPs assayed, as in our experiment, by agar well diffusion method were explained by authors as influenced by the capsular biopolymer composition (45). Also, a recent study (46) presented the biosynthesis of AgNPs for biomedical applications, mediated by extracellular pigment produced by Thalaromyces purpurogenus, with particles size from 4 to 41 nm diameter, polydispersed and stable, exhibiting a surface plasmon resonance at around 410 nm but a more variable shape of nanoparticles (spherical, hexagonal, rodshaped or triangular) than in the present research.…”

Sustainable microbial cell nanofactory for zinc oxide nanoparticles production by zinc-tolerant probiotic Lactobacillus plantarum strain TA4

“…This biosynthesis involved the formation and stabilisation of ZnO NPs. In addition, the EPS secreted by L. plantarum was reported in Garmasheva et al 's [15] study, where the reduction and biosorption of metal ion were involved, leading to the formation of NPs. However, this formation was contradicted with this study's finding as the TA4 strain investigated in this study did not produce EPS.…”

“…Furthermore, LAB efficacy in mediating the synthesis of ZnO NPs was observed in several studies [6,[9][10][11][12]. It was reported that LAB can produce selenium [13], gold [14], and silver NPs [15]. Overall, LAB is a useful cell factory for the formation of NPs due to these features.…”

Biosynthesis of zinc oxide nanoparticles by cell-biomass and supernatant of Lactobacillus plantarum TA4 and its antibacterial and biocompatibility properties

“…Moreover, using bacteria for the biosynthesis of ZnO NPs has significant advantages due to the production of functional biomolecules in the supernatant, which can reduce the metal ions into metal NPs 12,19 . In addition, the cell biomass of bacteria could act as a nanofactory in ZnO NPs' production due to the presence of a functional group on the bacterial cell that reduces the metal ions into metal NPs 20,21 .…”