## 3 Results
### Investigation of the Antimicrobial Properties of the Experimental Films  
Gelatin is a biodegradable, biocompatible, plastic, adhesive and low-cost biopolymer. Gelatin-based systems are applied in the food, packing, pharmaceutical and photography  
Figure 6: X-ray diffraction patterns: full pattern of silver-enriched gelatin–beetroot nanocomposite films (**a**) and pattern of gelatin (**b**). Figure 7: SEM image and EDX analysis of the silver-enriched beetroot–gelatin films: SEM image (**a**) and EDX spectra with indicated weighted contribution of chemical elements that were found in the produced films (**b**). industries. Due to their unique organoleptic properties, gelatin-based materials are promising materials for tissue engineering, drug delivery, wound dressing and gene therapy. On the other hand, gelatin has become an excellent growth medium for most bacteria due to the degradation or hydrolysis of gelatin in solution and due to microbial proliferation [27]. Since it is known that green-synthesized silver nanoparticles are effective in inhibiting the growth of both Gram-positive and Gram-negative bacteria [20], the antimicrobial properties of the beetroot-gelatin films containing silver nanoparticles were tested using agar diffusion methods. The results of the bioassays showed that the beetroot-gelatin films with silver nanoparticles exhibited antimicrobial activity against all the tested bacteria and _C. parapsilosis_ (Table 1). The inhibition zones of the beetroot-gelatin films with silver nanoparticles were between 1.0 and 4.0 mm and depended on the microorganism and/or the concentration of the silver nanoparticles in the films. Antifungal activity, however, was not observed in all the fungi cultures or in _Y. lipolytica_. It should be noted that the activity of the microorganisms was pH dependent. It was taken into account that the thermal stability and mechanical properties of the beetroot-gelatin films were dependent on the gelatin's molecular weight distribution, its amino acid composition and the pH of the film-forming solution. The variation of the pH allowed for the release of Ag nanoparticles from the gelatin-beetroot nanocomposite's network. Typically, Young's modulus, the stress break and the thermal stability of the gelatin films significantly decreased when the pH of the gelatin solution was higher than 9.0 or lower than 5.0. The triple-helix structure of the gelatin-based samples was not affected over the pH range of 5.0-9.0. The antimicrobial activity of the silver-enriched beetroot-gelatin samples produced using gelatin solutions with different pHs is shown in Table 2. It was found that the best antimicrobial properties were present in the experimental samples produced using the gelatin-based solutions that had pH = 3 and pH = 4 in the presence of _E. coli_ as well as pH = 7 and pH = 8 in the presence of _C. parapsilosis_ and _A. fumigatus_. This indicated that, by varying the samples' pHs, it was possible to control the antimicrobial effect of the Ag containing samples on the microorganisms. \begin{table}
\begin{tabular}{l l l l l l l l} \hline \hline \multirow{2}{*}{**Microorganism**} & \multirow{2}{*}{**
\begin{tabular}{l} **Control** \\ **(Beetroot juice)** \\ \end{tabular}} & \multicolumn{2}{l}{**BuAg10 UV**} & \multicolumn{2}{l}{**BuAg20 UV**} & \multicolumn{2}{l}{**BuAg30 UV**} & \multicolumn{2}{l}{**BuAg40 UV**} & \multicolumn{2}{l}{**BuAg50 UV**} \\ \cline{3-8}  & & \multicolumn{1}{l}{**Zone Size, mm**} & & & & & \\ \hline \multirow{4}{*}{_Escherichia coli_} & 3 & 0 & 12.0 \(\pm\) 0 & 13.5 \(\pm\) 0.5 & 12.5 \(\pm\) 0.5 & 12.5 \(\pm\) 0.5 & 13.0 \(\pm\) 0 \\ \cline{2-8}  & 4 & 0 & 22.0 \(\pm\) 0 & 17.5 \(\pm\) 0.5 & 19.0 \(\pm\) 0.5 & 22.5 \(\pm\) 0.5 & 20.0 \(\pm\) 0 \\ \cline{2-8}  & 7 & 0 & 0 & 7.6 \(\pm\) 0.3 & 0 & 0 & 0 \\ \cline{2-8}  & 8 & 0 & 0 & 0 & 0 & 0 & 0 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Antimicrobial effectiveness of Ag containing samples produced using gelatin solutions with different pHs.