## 3 Results and Discussion
### Monitoring the Volatile Compound Profiles in Seaweed Fermentation
#### 3.2.2 Laminaria
SC fermentation could significantly reduce 1-Octen-3-ol. In addition, a high content of alcohols was produced via fermentation, such as 1-pentanol (fermented, oily, sweet) and 1-hexanol (fruity, floral aromatic), which is consistent with our observations in the fermented _Uliva_ sp. (Table 1). The EMP pathway and Ehrlich pathway are two possible metabolic routes for converting carbohydrates and amino acids into branched alcohols during yeast fermentation, respectively [34]. Thus, more alcoholic compounds were identified in the _Laminaria_ sp. fermented with SC compared with the unfermented group. With regard to volatile acids, tetradecanoic acid was identified in the unfermented _Laminaria_ sp. and acid varieties, and total acid contents increased after microbial fermentation (Table 2). Saturated fatty acids, such as hexanoic acid (fatty, cheesy), octanoic acid (fatty, wavy) [20], and decanoic acid, were generated during microbial fermentation. In addition, a branched carboxylic acid (2-methylbutanoic acid) was identified only in _Laminaria_ fermented with BS. Based on the report of [PERSON] et al. [35], 2-methylbutanoic acid was identified in soybean products fermented with _Bacillus_ sp. Therefore, changes in volatile compounds in the unfermented and fermented _Laminaria_ sp. were demonstrated in the heat map (Figure 2). Compared with the unfermented _Laminaria_ sp., BS and SC seemed to significantly decrease aldehyde content during fermentation. In addition, BS fermentation enhanced ketone production, and SC fermentation boosted alcohol formation in fermented _Laminaria_ sp. suspensions, which were also observed in _Uliva_ sp. fermentation (Figure 1; Table 1). On the contrary, lactic acid bacteria (LA, LB, and LC) might slightly reduce aldehyde production when fermenting _Laminaria_ sp., compared with BS and SC. Based on changes in the profile of volatile compounds among fermentations, BS and SC have shown application potential in mitigating off-odors from seaweeds (_Uliva_ sp. and _Laminaria_ sp.) and modifying their aromatic perceptions after fermentation. Thus, principal component analysis (PCA) and odor analysis of fermented seaweeds were performed. Principal Component Analysis (PCA) of the Volatile Compounds in the Fermented Seaweeds 3.3.1. Ulva sp. The PCA of chemical groups of the volatile compounds in the unfermented and fermented _Uliva_ sp. is shown in Figure 3. The PCA can explain 84.1% of the total variances in the dataset (59.5% and 24.6% by principal component 1 [PC1] and principal component 2 [PC2], respectively). Based on the score plot (Figure 3A), the BS is in the first quadrant of the plot, whereas the unfermented _Uliva_ sp. is in the second quadrant. This result shows the difference in the composition of volatile compounds between the BS and the unfermented _Uliva_ sp. Moreover, in the loading plot (Figure 3B), the ketone family is observed in the positive axis of the PC1, whereas the aldehyde family is observed in the negative axis of the PC1. This negative correlation between the ketone and aldehyde family indicates the difference in volatile compounds between the BS and the unfermented _Uliva_. The aforementioned statement is supported by Table 1, i.e., ketones are increased, and aldehydes are reduced after BS fermentation. On the contrary, alcohol formation is associated with SC fermentation, which demonstrates the highest alcohol content among other fermentations. In evaluating the specific compound affecting the difference among fermentations, the PCA of a single volatile compound is shown in Figure 4. The PC1 and PC2 can explain 57.1% and 20.5% of the total variances in the dataset, respectively (total: 77.6%). Based on the score plot (Figure 4A), the BS and unfermented group are in a different quadrant of PC1, which correlates to Figure 3A. In addition, 2-heptanone is identified in the positive axis of PC1 in the loading plot (Figure 4B), which indicates that this compound likely affects the difference between the BS and the unfermented _Uliva_.