Table 1. Volatile profile of Bacillus amyloliqefaciens IN937a, B. subtilis GB03, and Paenibacillus polymyxa E681 using solid-phase micro extraction combined with gas chromatography–mass spectrometry.
| RT (min) | Compoundsa | VOC contents from PGPR strains (a.u. or µg)b c d | ||
| B. amyloliquefaciens | B. subtilis | P. polymyxa | ||
| Acohol | ||||
| 4.49 | Ethanol *$ | 10±3A | 7±2A | 2±0.3 BC |
| 6.36 | 1-propanol-2-methyl *$ | 29±3 A | 62±7A | 6±1.5B |
| 7.13 | 1-Butanol *$ | 3.6±0.6A | 3.4±0.3A | 0.5±0.04B |
| 8.49 | 1-Pentanol *$ | 66±3A | 0.4±0.04B | ND |
| 8.56 | 1-Butanol-3-methyl *$ | 3961±214A | 29±1B | 19±1.5B |
| 8.61 | 1-Butanol-2-methyl | 290±28A | 8±3B | 0.9±0.07B |
| 9.64 | 2,3-Butanediol *$ | 119±40A | 257±138A | 12±4B |
| Aldehydes | ||||
| 6.87 | Butanal-3-methyl | 29±3A | 77±5B | 15±1C |
| 7.04 | Butanal-2-methyl *$ | 0.3±0.03A | 0.06±0.01A | ND |
| 12.37 | 2,4-Hexadienal | TR | TR | 0.01±0.02 |
| 13.45 | Benzaldehyde *$ | 0.003±0.04A | 0.002±0.0003A | ND |
| Acids | ||||
| 9.74 | Glyoxylic acid | 1±0.2 A | 0.8±0.2A | 0.7±0.1A |
| 10.8 | Acetic acid diethyl | 6±0.5A | 36±5B | 2±0.1A |
| 11.10 | Butanoic acid-3-methyl *$ | 0.06±0.03A | 0.3±0.1A | 0.1±0.4B |
| Esters | ||||
| 6.11 | Ethyl acetate *$ | 21±3AB | 49±10A | 12±5A |
| 10.12 | Acetic acid butyl ester *$ | 2.8±0.2B | 0.1±0.02A | 4±1.5C |
| 11.40 | Butanol-3-methyl-acetate*$ 127 | 127±29 | TR | TR |
| 12.35 | 2-Butene-1-ol-3-methyl-acetate | 0.15±0.01A | 0.13±0.04A | 0.1±0.02A |
| Ethers | ||||
| 6.08 | Furan-2-methyl *$ | 0.04±0.001A | 0.1±0.009B | TR |
| 7.50 | Butane-1-methoxy-3-methyl *$ | 7530±512 | ND | ND |
| 7.60 | Furan-2-ethyl *$ | 0.03±0.01 | ND | ND |
| 8.83 | Furan-tetrahydro-2,5-dimethyl | 0.2±0.02 | TR | TR |
| 13.70 | Furan-2-pentyl *$ | 0.0005±0.0006A | 0.0006±0.0006A | 0.0003±0.0001A |
| Hydrocarbons | ||||
| 4.86 | Isoprene *$ | 483±109AB | 614±62B | 125±27A |
| 7.53 | Acetylene | 9±0.8A | 0.6±0.1B | 0.12±0.01C |
| 9.78 | Cyclohexane | 0.1±0.02A | 0.2±0.07A | ND |
| 15.42 | 1-Undecene | 0.8±0.3A | 1.2±0.1A | 0.4±0.06AB |
| 15.53 | 1-Undecane | 1.5±0.12AB | 3±0.2A | 0.2±0.03BC |
| 17.10 | Dodecane | 0.7±0.05A | 0.9±0.07A | 0.15±0.01B |
| 18.52 | Tridecane | ND | ND | 0.14±0.01A |
| Ketones | ||||
| 4.75 | Acetone *$ | 0.2±0.03A | 0.3±0.01A | 0.5±0.5AB |
| 5.74 | 2,3-Butanedione *$ | 38±4A | 77±8A | 14±3B |
| 5.85 | 2-Butanone *$ | 24±4B | 44±5A | 12±2C |
| 8.17 | Acetoin *$ | 153±22A | 226±37A | 74±12A |
| 10.16 | 2-hydroxy-3-pentanone *$ | 3.5±0.6A | 3.5±0.7A | 0.04±0.02B |
| S-containing compounds | ||||
| 4.37 | Methanethiol *$ | 0.6±0.1A | 0.1±0.01A | 0.3±0.09A |
| 8.67 | Dimethyl disulfide *$ | 4±0.1A | 2.4±0.2B | 2±0.2 BC |
| 13.48 | Dimethyl trisulfide | 0.12±0.02 | 0.18±0.01A | 0.1±0.01A |
| Inorganic compound | ||||
| 4.03 | Carbon dioxide | 1912±40A | 3907±150B | 1277±246A |
Compounds marked with * were identified by comparison of retention time (RT) and mass spectral data with those of authentic compounds. The others were identified by comparison of mass spectral data with those of NIST library.
Results are means of triplicate experiments; ND, not detected.
Values for compounds marked with $ are concentrations, expressed in µg/24 h. Values unmarked are expressed as relative peak areas to (Z)-3-hexenyl acetate (IS) expressed in arbitrary units (a.u.). The volatile profiling of B. amyloliquefaciens and B. subtilis was adapted from the previous publication [18]. It should be noted that all volatile measurements were acquired at same time and under similar conditions from 3 PGPR.
Values followed by the same letter within the same row are not significantly different (P>0.05).