## 3 Results
### MIC Determination of Cinnamaldehyde  
To compare the inhibitory ability of cinnamaldehyde, the minimum inhibitory concentration of eight destructive microorganisms was measured. As shown in Table 1, cinnamaldehyde for _Bacillus_ sp. (NK-NH15), _Bacillus_ sp. (NK-NH16), _B. megaterium_ (NK-NH10), _B. velezensis_ (NK-NH11), _B. tequilensis_ (NK-NH5) had inhibitory activity with respective MIC values of 1 mg/mL, 2 mg/mL, 0.125 mg/mL, 0.5 mg/mL and 1 mg/mL. Inhibition of Euxyl(r) K100 was somewhat more effective. _F. solani_ (NK-NH1) and _S. apiospermum_ (NK.W1-3) were more sensitive to cinnamaldehyde with MICs of 0.250, 0.0625 mg/mL, respectively. _S. apiospermum_ (NK.W1-3) was more sensitive to cinnamaldehyde than Euxyl(r) K100 (0.07813 mg/mL). Figure 3: Antimicrobial activity of cinnamaldehyde volatile gas in air (**A**) microbial growth on the dichotomy plate; left (bacteria), right (cinnamaldehyde250 uI/L). (**a**) _Bacillus_ sp. (NK-NH15), (**b**) _Bacillus_ sp. (NK-NH16), (**c**) _Bacillus_ sp. (NK-NH17), (**d**) _B. megaterium_(NK-NH10), (**e**) _B. velezensis_ (NK-NH11), (**f**) _B. tequilensis_ (NK-NH5), (**g**) _F. solani_ (NK-NH1), and (**h**) _S. apiospermum_ (NK.W1-3). (**B**) Inhibition rates of cinnamaldehyde against eight microorganisms to be tested. Cinnamaldehyde Inhibitory of Major Destructive Microbes of Hull during Laboratory Simulation Experiment  
To verify the inhibitory effect exerted by cinnamaldehyde in practical applications, we simulated the protection status of hull wood from Nanhai No. 1. Shipwreck hull scattered wood was put in deionized water for moisture stabilization treatment and preliminary desalination treatment in the tank. Bacterial suspension of _Bacillus_ sp. (NK-NH15), _Bacillus_ sp. (NK-NH16), _B. megaterium_ (NK-NH10), _B. veelezensis_ (NK-NH11) and _B. tequilensis_ (NK-NH5) was added in the water, then covered and the contact of wood with air was reduced (Figure S2). After standing for 14 days, the total number of bacteria in the water samples was determined. As shown in Table 2, the total number of bacteria in water samples without cinnamaldehyde was 4.27 \(\times\) 10\({}^{5}\)\(\pm\) 2.04 \(\times\) 10\({}^{4}\) CFU/mL. Cinnamaldehyde could inhibit microbial growth in water, and as the concentration of cinnamaldehyde rose, the number of microorganisms in the water continuously decreased. When the cinnamaldehyde concentration reached the highest value of 1.25 mg/mL, the total number of colonies in the water was 1.2 \(\times\) 10\({}^{1}\)\(\pm\) 5.10 CFU/mL. At the same time, the method of qPCR was applied to determine the biomass of bacteria in water samples. The correlation coefficient of the standard curve for _E. coli_ was \(>\)0.99 (Figure 4A). As shown in Figure 4B, the biomass of bacteria showed a decreasing trend with increasing concentrations of cinnamaldehyde. When the concentration of cinnamaldehyde was 1.25 mg/mL, the concentration of bacterial DNA was 1.34 \(\pm\) 0.09 ng/mL, which was significantly lower than that of the negative control (584.65 \(\pm\) 52.26 ng/mL). \begin{table}
\begin{tabular}{c c c} \hline \hline
**Strains** & **Cinnamaldehyde** & **Euxyl® K100** \\ \hline _Bacillus_ sp. (NK-NH15) & 1 & 0.07813 \\ _Bacillus_ sp. (NK-NH16) & 2 & 0.03906 \\ _Bacillus_ sp. (NK-NH17) & 1 & 0.03906 \\ _B. megaterium_ (NK-NH10) & 0.125 & 0.07813 \\ _B. peelezensis_ (NK-NH11) & 0.5 & 0.03906 \\ _B. tequilensis_ (NK-NH5) & 1 & 0.03906 \\ _F.solani_ (NK-NH1) & 0.25 & 0.1563 \\ _S. apiosperm_ (NK.W1-3) & 0.0625 & 0.07813 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: MIC values of cinnamaldehyde against destructive microorganisms of Nanhai No.1 (mg/mL).