## 3 Results and Discussions
### Antimicrobial Activity of Y-CNC and Yc Against Spoilage Microorganisms and Pathogens  
The MIC and MFC values for tested spoilage microorganisms were 1% (\(w/w\)) CLEO, while MBC was 2% (\(w/w\)) CLEO for _B. cereus_, _L. monocytogenes_, _S. aureus_ and _E. coli_. Based on these results the yeast films were functionalized with 2% CLEO. The evaluation of antimicrobial activity of control films with 2.00% CLEO against spoilage microflora indicated inhibition ranging between 27.99 \(\pm\) 1.97 mm against _Rhodotorula glutritis_, 23.60 \(\pm\) 0.68 mm against _Geotrichum candidum_, and 15.29 \(\pm\) 3.17 mm against _Bacillus cereus_ (Table 4). On the contrary, disk diffusion assay of antimicrobial activity of control films functionalized with 2.00% CLEO against the tested food borne pathogens demonstrated that they failed to exert any inhibition. A similar result was previously reported for essential oil included in films matrices, limiting their antimicrobial efficacy (e.g., whey protein isolate film functionalized with 7-9% sag EO [49]). \begin{table}
\begin{tabular}{c c c c c c c} \hline
**Test** **Microorganism** & **Y1c** & **Y2c** & **Y3c** & **Y1-CNC** & **Y2-CNC** & **Y3-CNC** \\ \hline \multicolumn{2}{c}{**Bacillus cereus**} & 14.95 \(\pm\) 0.35 c & 15.08 \(\pm\) 0.43 c & 15.29 \(\pm\) 3.17 c & 29.26 \(\pm\) 1.04 c & 33.49 \(\pm\) 3.12 c & 33.11 \(\pm\) 1.56 c \\ \multicolumn{2}{c}{_Geotrichum candidum_} & 21.00 \(\pm\) 0.30 b & 23.28 \(\pm\) 0.46 b & 23.60 \(\pm\) 0.67 b & 55.55 \(\pm\) 0.35 b & 54.07 \(\pm\) 0.51 b & 54.53 \(\pm\) 0.45 b \\ \multicolumn{2}{c}{_Rhodotorula glutritis_} & 27.01 \(\pm\) 0.57 a & 27.99 \(\pm\) 1.97 a & 26.44 \(\pm\) 0.38 a & 62.85 \(\pm\) 0.41 a & 59.02 \(\pm\) 0.66 a & 62.80 \(\pm\) 0.45 a \\ \multicolumn{2}{c}{_Listeria monocytogenes_} & nd & nd & nd & 13.00 \(\pm\) 0.00 d & 12.50 \(\pm\) 0.05 d & 12.50 \(\pm\) 0.05 d \\ \multicolumn{2}{c}{_Staphylococcus aureus_} & nd & nd & nd & 11.75 \(\pm\) 0.03 d & 11.75 \(\pm\) 0.03 d & 12.00 \(\pm\) 0.00 d \\ \multicolumn{2}{c}{_Escherichia coli_} & nd & nd & nd & 10.25 \(\pm\) 0.03 d & 11.00 \(\pm\) 0.00 d & 11.00 \(\pm\) 0.00 d \\ \hline \end{tabular}
\end{table} 
Table 4: Antimicrobial activity of yeast films. Results are average \(\pm\) SD of two independent replicates, expressed in mm. nd—not detected. Figure 5: Heat map showing the retention rate of VOCs (%) by the yeast films in comparison with CLEO (**a**) and dendogram (**b**). Grafting CNC in yeast films improved approx. 2 times their antimicrobial activity against all tested spoilage microflora, inhibition diameters reaching approx. 62.85 \(\pm\) 0.45 mm against _R. glutinis_, 55.55 \(\pm\) 0.35 mm against _G. candidium_, and 33.49 \(\pm\) 3.12 mm against _B. cereus_. Moreover, the grafted CNC yeast films exerted antibacterial activity against all three tested pathogens, ranging 11-13 mm, significantly different (_p_ < 0.05) from the antimicrobial activity against spoilage microorganisms. These findings were confirmed by [8] who reported an increase up to 80% in antimicrobial activity of whey protein films with 10% grafted bacterial cellulose, functionalized with oregano essential oil against food borne pathogens such as _Staphylococcus aureus_, _Listeria monocytogenes_, _Salmonella enteritidis_, and _Pseudomonas aeruginosa_, with higher inhibition against Gram-positive bacteria [8]. A plausible explanation for this spectacular increase in antibacterial activity could be connected to the altered morphology of cellulose functionalized films, with increased retention capacity due to surface irregularities and release profile of essential oils, hypothesis which is sustained by the GC/MS volatile fingerprint of the yeast films. The antibacterial activity of eugenol, present in CLEO from cinnamon essential oil and in functionalized CLEO yeast film as indicated by GC/MS analysis, was previously reported against _L. monocytogenes_.