## 4 Discussion  
The present archaeological digging work of Nanhai No. 1 is close to its end, with the hull chronically exposed to air and with high hull humidity (74.3%), which provides a suitable growth environment for microbial growth. Microorganisms, on the one hand, can affect the aesthetics of cultural relics, and on the other hand can cause harm to the cultural relics themselves. So, in the process of cultural relic protection, the prevention and control of microorganisms is of great significance. Previous studies have found that Nanhai No. 1 is affected by multiple microorganisms. _F. solani_ (NK-NH1) is the major destructive fungus on ship wood, accounting for 90% of the total fungal load on the hull, which presents white plaques [8]. _S. apiosperm_ (NK. W1-3) is a major destructive fungus in water samples stored in shipw wood. The genus _Scedosporium_ accounted for 72.28% of the total fungi in water samples. _B. tequilensis_ (NK-NH5), _B. velezensis_ (NK-NH11), _B. megaterium_ (NK-NH10) were the main bacteria in water samples storing wooden lacquer plates, _Bacillus_ sp. (NK-NH15), _Bacillus_ sp. (NK-NH16), _Bacillus_ sp. (NK-NH17) were the main harmful bacteria isolated on ship wood. These destructive microorganisms can degrade cellulose and lignin, causing irreversible effects on hulls. Currently, the main measures for controlling microbial degradation of Nanhai No. 1 are to moisturize and inhibit the hulls by spraying them with distilled water containing 0.5% Euxyl(r) K100. Although the process can be effective in controlling microbial degradation of the hull, once the use of bacteriostatic agents is discontinued, the microorganism undergoes substantial reproductive growth. At the same time, Euxyl(r) K100 was found to cause some negative effects on the archaeological and relic protection workers' bodies. As such, finding safer and more environmentally friendly ways to inhibit these destructive microorganisms is very important. The aim of this study was to investigate the inhibitory activity of cinnamaldehyde against the destructive microorganisms of Nanhai No. 1. We first show that these destructive microorganisms are potentially harmful to hulls. Cellulose degradation experiments found that except for _B. velezensis_ (NK-NH11), other microorganisms to be tested had the ability to degrade cellulose. The prevention and treatment of destructive microorganisms of Nanhai No. 1 should take both fungi and bacteria into account. Meanwhile we determined the antimicrobial activity of cinnamaldehyde. Previous studies have reported that cinnamaldehyde has a broad spectrum of antimicrobial activity [17; 19; 28; 29]. We first preliminarily measured the inhibition of destructive microorganisms of Nanhai No. 1 by the disk diffusion method and found that cinnamaldehyde, at a certain concentration, could effectively inhibit microbial growth, which was comparable to the effects of Euxyl(r) K100 at 0.5%. At the same time, we found that fungi were more sensitive to cinnamaldehyde. Taking into  
Figure 4: Quantification of bacterial biomass of samples by qPCR. (**A**) Standard curve for _E. coli_ quantification using bacterial primers Eub338/Eub518. (**B**) Comparison of bacterial amounts. N: Water samples without cinnamaldehyde addition; C1: cinnamaldehyde concentration at 50 \(\upmu\)g/mL; C2: cinnamaldehyde concentration at 200 \(\upmu\)g/mL; C3: cinnamaldehyde concentration at 500 \(\upmu\)g/mL; and C4: cinnamaldehyde concentration at 1250 \(\upmu\)g/mL. account the volatile properties of cinnamaldehyde, we measured the inhibition effect of cinnamaldehyde volatile gas in air. Similarly to the paper disk diffusion method results, airborne cinnamaldehyde can effectively inhibit microbial growth, although the inhibition effect is more obvious on fungi. Cinnamaldehyde, through its volatile properties, exerts antimicrobial ability, which can be used on the inhibition of destructive microorganisms of cultural relics in practical work.