## 3 Results and Discussion
### Antimicrobial Properties of the Films  
In Figure 5, the pictures of the inhibition zones revealed in the case of agar disc diffusion tests against the selected pathogen microorganisms, i.e., _E. coli_, _S. typhimurium_, and _S. aureus_, are compared, and the evaluation of the antibacterial action is reported \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Sample** & **Thickness (mm)** & **Water Solubility** & \
\begin{tabular}{c} **WVP** \\ **(g\(\cdot\)mm/kPa\(\cdot\)h\(\cdot\)m\({}^{2}\))** \\ \end{tabular} &
\begin{tabular}{c} **Total Color** \\ **Differences (\(\Delta\)E)** \\ \end{tabular} & **Opacity** \\ \hline \hline Starch-PVA 40:60 (SP) & 0.066 \(\pm\) 0.002 a & 79.0 \(\pm\) 3.2 a & 0.41 \(\pm\) 0.02 a & 3.55 \(\pm\) 0.11 c & 0.47 \(\pm\) 0.04 a \\ \hline SP+1\% CNPs & 0.067 \(\pm\) 0.003 a & 77.6 \(\pm\) 1.2 a & 0.38 \(\pm\) 0.03 a & 3.75 \(\pm\) 0.18 c & 0.79 \(\pm\) 0.08 b \\ \hline SP+3\% CNPs & 0.069 \(\pm\) 0.002 a & 74.1 \(\pm\) 1.3 b & 0.33 \(\pm\) 0.01 b & 4.08 \(\pm\) 0.08 b & 1.34 \(\pm\) 0.19 c \\ \hline SP+5\% CNPs & 0.070 \(\pm\) 0.003 a & 71.8 \(\pm\) 0.5 c & 0.28 \(\pm\) 0.03 c & 4.37 \(\pm\) 0.12 a & 1.77 \(\pm\) 0.29 d \\ \hline \hline \end{tabular}  
* Starch-PVA 40:60 (or SP as control film sample), starch-PVA loaded with 1% CNPs (SP+1% CNPs), starch-PVA film loaded with 3% CNPs (SP+3% CNPs), and starch-PVA film loaded with 5% CNPs (SP+5% CNPs). Results are presented as the mean \(\pm\) standard deviation. Different letters in each column indicate statistically significant differences at \(p<0.05\).  
\end{table} 
Table 2: Physical properties of starch-PVA nanocomposite films loaded with different amounts of CNPs. in Table 3 on the basis of the inhibitory area size. As expected, no inhibition zone was evidenced in the case of the neat starch/PVA film, whereas the composite samples were characterized by a progressive increment of the inhibition zone diameter with the CNP concentration. In detail, the 1% CNPs addition was only efficient at reducing the growth of _S. aureus_. By increasing the CNPs concentration up to 3-5%, a progressive antibacterial activity was revealed. These experimental findings confirmed that the antimicrobial features were provided by the addition of CNPs, in agreement with previous studies [31]. CNPs can act as antimicrobial agents due to their hydrophobic and chelating nature in pH higher than pKa or neutral pH [41]. A partial and medium inhibitory effect was observed against _E. coli_ and _S. typhimurium_ for 3 and 5% CNPs, respectively, and a high inhibitory (11.78 mm) action against the _S. aureus_ growth was seen in both cases. These experimental findings confirm the higher inhibitory activity of CNPs against Gram-positive bacteria compared to Gram-negative bacteria. [PERSON] and [PERSON] [42] reported that Gram-positive bacteria  
Figure 5: Pictures of the inhibition zones revealed in the case of agar diffusion test against _S. aureus_, _E. coli_ and _S. typhimurium._ Starch-PVA 40:60 (or SP as control film sample), starch-PVA loaded with 1% CNPs (SP+1% CNPs), starch-PVA film loaded with 3% CNPs (SP+3% CNPs), and starch-PVA film loaded with 5% CNPs (SP+5% CNPs).