## 3 Results  
### Comparison of Natural and Synthetic Community for Red Rice Wine Fermentation  
#### 3.1.1 Ethanol and Organic Acid Production during Red Rice Wine Processing  
Previous studies reported that Cambodian traditional fermentation starter (natural community) contains _Rhizopus oryzae_ as the main filamentous fungi, _Saccharomyces cerevisiae_ as the main fermenting yeast, and _Lactobacillus plantarum_ as the main lactic acid bacteria. Additionally, the presence and co-occurrence of these three microbial strains were associated with the generation of major flavor compounds. In this study, red rice wine fermentation kinetics were investigated for both culture with a natural community and synthetic community made of _R. oryzae_, _S. cerevisiae_ and _L. plantarum_. Sugar, ethanol, and organic acids play important roles in wine taste and quality; accordingly, these parameters were investigated during the process (Figure 1). The time evolution of ethanol and organic acid production was correlated with the consumption of glucose. Maltose and glucose were the main reducing sugars detected in this study (Supplementary Figure S1). Surprisingly, synthetic communities comprising high yeast inoculant (i.e., _Ro-Sc_ 1:10 and _Ro-Sc-Lp_ 1:10:1) did not lead to the highest ethanol production. This type of observation has been made previously for Chinese fermented beverages [26]. According to Table 1, the significant highest ethanol productions were observed when using the natural community, followed by the community _Ro-Sc-Lp_ 1:1:1. Whereas the natural community gave the highest ethanol yield, it also led to the accumulation of acetic acid levels, two compounds considered as off-flavor compounds for wine. \begin{table}
\begin{tabular}{c c c c c c c} \hline
**Concentration** & **Natural Community** & \begin{tabular}{c} _Ro-Sc-Lp_ \\ **1:1:1** \\ \end{tabular} & \begin{tabular}{c} _Ro-Sc-Lp_ \\ **1:10:1** \\ \end{tabular} & \begin{tabular}{c} _Ro-Sc_ \\ **1:1** \\ \end{tabular} & \begin{tabular}{c} _Ro-Sc_ \\ **1:10** \\ \end{tabular} & \begin{tabular}{c} _Ro-Sc_ \\ **1:0** \\ \end{tabular} & \
\begin{tabular}{c} _Ro-Sc_ \\ **1:0** \\ \end{tabular} &
\begin{tabular}{c} _Ro-Sc_ \\ **1:0** \\ \end{tabular} \\ \hline Ethanol (\% _v/v_) & 10.73 \(\pm\) 0.07 \({}^{\text{a}}\) & 9.95 \(\pm\) 0.02 \({}^{\text{b}}\) & 6.5 \(\pm\) 0.41 \({}^{\text{d}}\) & 10.17 \(\pm\) 0.32 \({}^{\text{b}}\) & 7.95 \(\pm\) 0.13 \({}^{\text{c}}\) & 8.41 \(\pm\) 0.80 \({}^{\text{c}}\) \\ Acetic acid (g/L) & 2.99 \(\pm\) 0.02 \({}^{\text{a}}\) & 1.81 \(\pm\) 0.06 \({}^{\text{c}}\) & 2.54 \(\pm\) 0.13 \({}^{\text{b}}\) & 0.52 \(\pm\) 0.02 \({}^{\text{d}}\) & 0.37 \(\pm\) 0.01 \({}^{\text{d}}\) & 0.40 \(\pm\) 0.18 \({}^{\text{d}}\) \\ Acetic acid (g/L) & 3.58 \(\pm\) 0.13 \({}^{\text{a}}\) & 2.95 \(\pm\) 0.14 \({}^{\text{b}}\) & 4.45 \(\pm\) 0.43 \({}^{\text{a}}\) & 1.64 \(\pm\) 0.01 \({}^{\text{c}}\) & 1.23 \(\pm\) 0.30 \({}^{\text{c}}\) & 1.58 \(\pm\) 0.20 \({}^{\text{c}}\) \\ \hline \end{tabular} Values in a row that are not preceded by the same letter are significantly different (\(p\leq 0.05\)).  
\end{table} 
Table 1: Final concentration of ethanol and organic acids at day 10, the end of the traditional rice wine brewing process. 1.2 Comparative Analysis of the Impact of Natural and Synthetic Communities on the Flavor Profile during Red Rice Wine Fermentation  
Flavor and aroma profiles are important factors responsible for the organoleptic quality of wine. In this study, flavors compounds produced during the fermentation process were analyzed to investigate and evaluate the efficiency of natural and synthetic communities. Thirty-nine volatile compounds, including alcohol, ester, acid, aldehyde, and ketone, were identified in rice wine mash by HS-SPME-GCMS (Table 2). The use of _L. plantarum_ in the brewing process resulted in increased production of the following flavor compounds: isoamyl acetate, phenethyl acetate, ethyl octanoate, ethyl lactate, ethyl acetate, and isoamyl alcohol.