## 3 Results and Discussion
### In Vitro Antibacterial Activity  
Antibacterial activity of the obtained CNC and LNP from both HP and HS were tested on Xac at different concentrations and at different times by using a microdilution method. After 24 h, the most interesting and highly statistical significant results were noted for each sample tested at the concentration of 0.5 and 1% _w/v_: both CNC and LNP showed an inhibition activity comparable to the one displayed by copper oxychloride (Figure 10a). After 48 h, a general reduction of growth inhibition was observed for all tested substances, except for copper, although a highly statistical difference could be still appreciated (Figure 10b). A general, strong dose-dependent activity was noted. The antibacterial mechanisms of cellulose nanoforms are still largely unknown. Several works have reported the cellulose nanofibrils' ability to disturb bacteria swimming motility in several foodborne pathogens (_E. coli_, _L. monocytogenes_, _B. aureus_ and _S. typhimurium_) or, as shown for _E. coli_ and _P. aeruginosa_, the CNC capacity to prevent bacterial cell adhesion and biofilm formation [82; 83; 84]. Noteworthily, [PERSON] et al. (2021) linked bacterial growth inhibition by CNC to the loss of cell membrane integrity in _E. coli_ bacterial cells [85]. This effect was ascribed to the disrupting action of CNC on the membrane phospholipid  
Figure 9: Total phenolic content of obtained LNP, measured by the Folin–Ciocalteu method. Results are expressed as gallic acid equivalents (GAE). Data are represented as the mean and SD, and different letters show significantly different values (_p_ < 0.01) upon one-way ANOVA followed by [PERSON]’s LSD post hoc test.  
structure. Other authors suggest that one of the antibacterial modes of action of CNC could be explained through the depletion effect recorded on _P. aeruginosa_ and _P. fluorescens_. In these works, the flocculation of the bacterial cells was observed in CNC suspension that impaired cell adhesion capacity and thus biofilm formation [84; 86]. Naturally, a simultaneous effect of all previously cited antimicrobial mechanisms cannot be ruled out. In this context, more studies are needed to clarify the prevalent mode of action of CNC on Xac.  
To the best of our knowledge, this report is the first describing the CNC antimicrobial activity on a plant pathogenic bacterium.  
Lignin antimicrobial properties are instead well known: several works highlight the possibility of using LNPs as promising nanopesticides or nanocarriers against different pathogenic bacteria [87; 88]. However, the hypothetical antimicrobial modes of action of LNP against bacterial cells are multiple. LNP are supposed to penetrate the cell wall provoking membrane lysis, reacting with ROS species and inducing oxidative stress, generating a depletion in ATP and a decrease of intracellular pH, resulting in cell death [89; 90; 91]. Most of these action mechanisms are related to LNP size and composition. The final amount of polyphenols seems to represent a major driver for LNP antimicrobial activity [92; 93]. However, our results indicate lack of correlation between LNP antibacterial action and TPC amount, suggesting that different modes of action may concur to LNP antibacterial properties.