# Antibacterial Activity of Green Synthesised Silver Nanoparticles on _Saccharomyces cerevisiae_
## 3 Results and Discussion
Therefore, the results of the present study show antibacterial activity correlated with those described in other studies. In addition, this study has expanded information on the antibacterial action of nanoparticles in the yeast synthesis model. To establish the MICs, summary data on antibacterial activity were used, and the final concentrations of silver nanoparticles in the samples were determined by the qualitative-quantitative reaction. Thus, the MIC was determined based on the results of the MTT test. Summary results are presented in Table 2.  
Figure 6: Value of adhered cells after subculturing with supernatant (crystal violet). The yeast extracts were obtained from samples of yeast _S. cerevisiae_ 71B, cultured in 20% glucose solution with the addition of: (1) sterile dH\({}_{2}\)O, (2) 0.5 mM AgNO\({}_{3}\), (3) 1.0 mM AgNO\({}_{3}\), (4) 1.5 mM AgNO\({}_{3}\) and (5) 2.0 mM AgNO\({}_{3}\). * \(p\) < 0.05. It was established that the lowest concentration of silver ions was sufficient for the manifestation of effective antibacterial action, despite the fact that a significant difference has been found between the samples in previous experiments. This indicates that there may be some effect of the conditions of the experiment, namely the concentration of a solution of silver nitrate added at the beginning of the experiment. It should be noted that against clinical strains of _S. aureus_ 1536 and _K. pneumoniae_ 520, silver ions had antibacterial activity in lower concentrations than against test cultures of _S. aureus_ ATCC 25923 and _E. coli_ ATCC 25922. Moreover, the MIC was established based on the results of the study of the effect on the adhesion property of bacterial cells. Summary results are presented in Table 3.  
Supernatant samples performed better because MICs were lower than in the yeast extract samples. Moreover, this coincides with the results of determining the MIC on the MTT test. Comparing the results obtained from two studies of antibacterial activity of the samples, the concentrations effective against _S. aureus_ ATCC 25923, _E. coli_ ATCC 25922, _S. aureus_ 1536 and _K. pneumoniae_ 520 were 0.04 mM contained in the supernatant. In the study of the antibacterial action of the nanoparticles obtained, the synthesised nanoparticles based on yeast extract were found to have less antibacterial activity compared with the use of the supernatant. This can be explained by the fact that the composition of the yeast extract and the supernatant is different, which may affect the stabilisation of the nanoparticles. Moreover, according to the literature, depending on which resource is used for the synthesis of silver nanoparticles, the type of antibacterial action--bacteriostatic or bactericidal [19]--is determined. This directly depends on the type of plugging and stabilising substances in the biological object used. Many variants of silver nanoparticle biosynthesis are described--algae or plants or their extracts, heterotrophic eukaryotic cell lines and numerous prokaryotes. The shape, degree of dispersion of the obtained colloids, and biological properties and their manifestation can vary from one green approach to another [20; 21]. While the biological substances used for the synthesis of nanomaterials consist of similar or identical active ingredients, very often the effect of the obtained nanoparticles, especially on living cells, can vary significantly [22]. Depending on the cultivation conditions, pH value, the composition of the medium and temperature, when using the yeast _Saccharomyces cerevisiae_, stabilising agents can include ethanol and phenols, carboxylic acids and aromatic amines. Since the nanoparticles described showed antibacterial activity against _Staphylococcus aureus_, it could be assumed that in the present study these