Table 1.
The main classes of VOCs produced by B. subtilis CF-3 after different fermentation durations.
| Class | Relative content (%) | |||||||
|---|---|---|---|---|---|---|---|---|
| 12hFL | 24hFL | 36hFL | 48hFL | 60hFL | 72hFL | 84hFL | 96hFL | |
| Alcohols | 15.03 ± 0.38 d | 11.60 ± 0.34 e | 12.64 ± 0.28 c | 9.63 ± 0.12 a | 24.41 ± 0.48 b | 5.95 ± 0.15 g | 8.24 ± 0.29 f | 5.26 ± 0.23 h |
| Number of alcohols | 13 | 12 | 13 | 14 | 14 | 14 | 14 | 13 |
| Ketones | 22.54 ± 1.28 c | 18.03 ± 0.92 d | 15.62 ± 1.09 b | 10.56 ± 0.35 a | 11.15 ± 0.68 d | 15.04 ± 0.82 e | 16.55 ± 1.25 e | 7.40 ± 0.52 f |
| Number of ketones | 14 | 13 | 9 | 15 | 14 | 12 | 13 | 9 |
| Pyrazines | 0.55 ± 0.05 b | 0.05 ± 0.02 b | 0.35 ± 0.12 b | 3.50 ± 0.73 a | 0.07 ± 0.02 b | 0.09 ± 0.03 b | 0 b | 0 b |
| Number of pyrazines | 3 | 1 | 2 | 3 | 1 | 1 | 0 | 0 |
| Esters | 2.68 ± 0.52 cd | 3.68 ± 0.86 c | 8.99 ± 1.92 a | 3.00 ± 0.49 b | 1.40 ± 0.28 cd | 0.33 ± 0.08 d | 0.81 ± 0.29 d | 0.30 ± 0.11 d |
| Number of esters | 3 | 2 | 3 | 3 | 1 | 1 | 2 | 1 |
| Acids | 17.06 ± 2.93 b | 13.53 ± 2.01 bc | 4.30 ± 0.98 cd | 10.66 ± 1.87 a | 4.03 ± 0.51 de | 6.22 ± 0.69 de | 7.37 ± 1.28 de | 7.83 ± 0.77 e |
| Number of acids | 5 | 4 | 5 | 9 | 6 | 3 | 5 | 3 |
| Phenols | 8.49 ± 2.35 ab | 13.71 ± 3.89 a | 4.39 ± 1.52 ab | 2.96 ± 0.68 a | 4.51 ± 1.25 b | 2.87 ± 0.48 c | 2.72 ± 0.92 c | 2.91 ± 1.04 c |
| Number of phenols | 4 | 3 | 4 | 5 | 3 | 3 | 3 | 3 |
| Hydrocarbons | 0 c | 0 c | 3.81 ± 0.95 b | 3.42 ± 0.52 a | 1.01 ± 0.18 c | 0 c | 1.50 ± 0.32 c | 0 c |
| Number of hydrocarbons | 0 | 0 | 1 | 3 | 2 | 0 | 1 | 0 |
| Amines | 15.84 ± 2.09 b | 0.14 ± 0.03 c | 0.49 ± 0.15 c | 12.86 ± 2.94 a | 1.69 ± 0.39 c | 0.60 ± 0.16 c | 0.22 ± 0.09 c | 0.39 ± 0.04 c |
| Number of amines | 2 | 1 | 1 | 2 | 2 | 1 | 1 | 1 |
| Aldehydes | 2.17 ± 0.68 c | 7.73 ± 1.29 a | 1.67 ± 0.38 b | 0.61 ± 0.13 c | 1.60 ± 0.27 c | 2.11 ± 0.54 cd | 1.44 ± 0.20 c | 1.28 ± 0.44 c |
| Number of aldehydes | 2 | 2 | 2 | 2 | 2 | 2 | 2 | 2 |
| Ethers | 12.98 ± 2.23 c | 17.71 ± 2.96 bc | 6.63 ± 0.93 bc | 9.57 ± 1.38 a | 13.70 ± 2.40 b | 27.05 ± 3.95 b | 18.99 ± 3.29 c | 15.72 ± 2.37 d |
| Number of ethers | 3 | 4 | 3 | 3 | 4 | 4 | 3 | 2 |
| Others | 2.66 ± 0.39 e | 13.77 ± 2.67 de | 41.11 ± 7.93 b | 33.23 ± 5.23 a | 36.44 ± 8.30 c | 39.74 ± 6.09 d | 42.17 ± 4.94 d | 58.89 ± 6.82 d |
| Number of others | 2 | 2 | 4 | 3 | 2 | 2 | 4 | 2 |
| Total peak area of all possible VOCs | 5004596 ± 425236 d | 4620461 ± 521412 d | 11527435 ± 796523 b | 19971460 ± 841253 a | 7622145 ± 532115 c | 3597881 ± 501027 e | 3179336 ± 489365 e | 1961563 ± 141255 f |
| Number of all possible VOCs | 51 | 44 | 47 | 62 | 51 | 43 | 48 | 36 |
The compounds possibly generated by CF-3 were identified by comparing their mass spectra to those in the NIST Mass Spectral Library (probability-based match >85%). Values are expressed as means of the relative content of each class (n = 3). To express the variation of the VOCs more accurately, peak area (relative content (%) × total peak area of all possible VOCs) was used in ANOVA. The different letters represented significant differences (P < 0.05) between the B. subtilis CF-3 fermentation liquids for different fermentation durations.