## 2 Results and Discussion
### Principal Component Analysis of Fermented Rice Samples according to Strains of LABs  
The present study applied principal component analysis (PCA) to compare the differences of volatile and nonvolatile compounds among the fermented rice samples according to strains of LABs. The PCA score plot of volatile compounds in Figure 1A shows that rice samples fermented by _Lac. sakei_ could be distinguished from the others along the PC1 dimension (explaining 42.5% of the variance). In addition, rice samples fermented by obligatorily homofractative/facultatively heterofractative LABs, such as LPC, RTJL3, RTCL16, RTCL79, RTCL3, and RTCL31, were separated from fermented rice samples inoculated with obligatorily heterofractative lactic acid bacteria, such as KR10, KR7, RTJL4,JKA1-6, JKF2-2, and RTCL9, along the PC2 dimension (explaining 23.0% of the variance). The PCA loading plot of volatile compounds in Figure 1B shows that 2-ethylfuran, 2-propylfuran, 2-butylfuran, 2-pentylfuran, hexanal, 2-methylbutanal, pentan-1-ol, and butan-1-ol were closely correlated with RTCL16. On the other hand, ketones and aldehydes, such as butane-2,3-dione, 3-hydroxybutan-2-one, 6-methylhept-5-en-2-one, 2-methylbutanal, and nonanal, were related to the positive axis of the PC2 dimension. PCA analysis was performed to compare the differences among the fermented rice samples according to strains of LABs. The PCA score plot of volatile compounds in Figure 1A shows that rice samples fermented by LAB inoculated with _Lac. sakei_ could be distinguished from the others along the PC1 dimension (explaining 42.5% of the variance). In addition, rice samples fermented by obligatorily homoformerative/facultatively heterofermentative lactic acid bacteria, such as LPC, RTJL3, RTCL16, RTCL79, RTCL3, and RTCL31, were separated from fermented rice samples inoculated with obligatorily heterofermentative lactic acid bacteria, such as KR10, KR7, RTJL4, JKA1-6, JKF2-2, and RTCL9, along the PC2 dimension (explaining 23.0% of the variance). The PCA loading plot of volatile compounds in Figure 1B shows that 2-ethylfuran, 2-propylfuran, 2-butylfuran, 2-pentylfuran, hexanal, 2-methylbutanal, pentan-1-ol, and butan-1-ol were closely correlated with RTCL16. On the other hand, ketones and aldehydes, such as butane-2,3-dione, 3-hydroxybutan-2-one, 6-methylhept-5-en-2-one, 2-methylbutanal, and nonanal, were related to the positive axis of the PC2 dimension.  
The PCA score plot of nonvolatile compounds in Figure 2A shows that rice samples fermented by obligatorily heterofermentative LAB such as JKA1-6, JKF2-2, and RTCL9 could be distinguished from the other samples (except for KR10, KR7, and RTJL4) fermented with obligatorily homoformerative/facultatively heterofermentative LABs along the PC1 axis (explaining 25.40% of the variance). Also, in contrast to the score plot for nonvolatile compounds, RTCL16 was not clearly separated from the other samples along the PC2 axis (explaining 22.6% of the variance). The PCA loading plot of nonvolatile compounds in Figure 2B shows that most carbohydrates (except for sucrose and maltose) were strongly associated with rice samples fermented by obligatorily heterofermentative LABs (KR10, KR7, RTCL9, JKA1-6, and JKF2-2) on the positive dimension of the PC1 axis of the PCA score plot. On the other hand, some amino acids (serine, valine, isoleucine, phenylalanine, glycine, and ornithine) and organic acids (lactic acid, succinic acid, propanoic acid, oxal  
Figure 1: Principal component analysis (PCA) plots of the volatile compounds identified in fermented rice according to strains of LABs: (**A**) score plot, (**B**) loading plot.  
were mainly responsible for rice samples fermented by heteroformative LABs (KR10 and KR7) on the positive axis of the PCA score plot along the PC2 dimension. Thus, these compounds could be major nonvolatile compounds related to rice samples fermented by the obligatorily heteroformative LABs (KR10, KR7, RTCL9, JKA1-6, and JKF2-2).