# Recent Advances in Bio-Based Wood Protective Systems: A Comprehensive Review
## 4 Bio-Based Fillers
### Bio-Based Additives for Antimicrobial Wood Systems
The outcomes of the antifungal evaluations revealed that b-citronello, geraniol, carvacrol, thymol, eugenol, and citral exhibited noteworthy antifungal properties against all three fungi under examination. These findings underscore the potential of carvacrol for future development as a natural fungicidal agent, suggesting the need for further investigation into its potential for wood preservation treatments. Natural oils represent another category with efficient fungicidal performance, specifically analysed in recent years. For example, [PERSON] et al. [121] examined the antifungal effects of essential oil from _Pelargonium gravelens_ and its constituent fractions on four wood-decaying fungi (_C. puteana_, _Coriolus versicolor_, _Poria placenta_, and _G. trabeum_). Their aim was to showcase the value of Moroccan aromatic and medicinal plants. The study revealed impressive outcomes, implying the potential utilization of this substance for safeguarding wood against fungal deterioration. Likewise, a recent study concentrated on creating an environmentally conscious wood preservative solution using distillate derived from the pyrolysis of coconut shells (CSPOD) [101]. The notable presence of phenolic compounds within the oil distillate conferred considerable resistance to decay in the treated wood, effectively combatting both white-rot and brown-rot fungi. Consequently, the potential exists for CSPOD to be refined into a formulation for wood preservation. Another study revealed the efficient antifungal activity of an essential oil extracted from the Brazilian savannah species _Lippia organoides Kunth_ against _G. trabeum_ and _T. versicolor_[103], while [PERSON] et al. [104] analysed the positive antifungal activity of six plant essential oils (_Origanum vulgare_, _Cymbopogon citratus_, _Thymus vulgaris_, _Pelargonium gravelens_, _Cinnamomom zeylanicum_, and _Eugenia carophyllata_) against the wood-rot fungi. Similarly, [PERSON] et al. [48] assessed the effectiveness of Norway spruce and beech wood treated with linseed and tung oil in resisting wood-decay fungi. Finally, [PERSON] et al. [15] examined the response of fungi to a sustainable thermoset composed of epoxidized soybean oil (ESO), castor oil maleic anhydride adduct (COMA), and methyl nadic anhydride (MNA), demonstrating effective fungal resistance offered by the environmentally friendly coating. In addition to being a positive reinforcing filler, cellulose has been shown to act as a bio-based fungicidal additive. [PERSON] et al. [117] enhanced a standard commercial acrylic varnish by incorporating CNC and lignin sourced from beech wood. However, the resulting protection against bacterial deterioration was found to be inadequate. On the other hand, in another work, CNC led to an enhancement in fungal resistance [118]. This improvement was evident through decreased mass loss and changes observed in FTIR spectroscopy, attributed to the formation of crosslinks. These crosslinks also contributed to a reduction in water absorption. Likewise, lignin can be utilized in fungicidal applications, as emphasized in the research conducted by [PERSON] et al. [122]. They investigated the effectiveness of lignin nanocapsules containing the fungicide propiconazole as an environmentally friendly wood preservative. The innovative preservation approach displayed improved capacity to resist fungal activity when compared with the individual components. Additional extracts from wood, such as tannins, can exhibit remarkable antimicrobial capabilities. [PERSON] et al. [95] directed their attention towards utilizing condensed tannins sourced from conifer trees as eco-friendly alternatives to synthetic wood preservatives. They extracted eight distinct tannin fractions from spruce cones, spruce banks, and pine cones. The research findings highlighted that, even at minimal concentrations, these tannins effectively restrained the growth of brown-rot fungi. On the other hand, [PERSON] et al.