The producing strain Bacillus subtilis PJS was isolated from the leaf of an unidentified plant collected at Luopu county, Hetian area, Xinjiang Province, People’s Republic of China. On the basis of analysis of 16S rRNA, it was identified as Bacillus subtilis subsp. inaquosorum. A stock culture of the strain Bacillus subtilis PJS was maintained on modified Gause's no. 1 agar slant consisting of soluble starch (Beijing Qi Te Xin Chemical Co. Ltd. China) 20.0 g, NaCl 50.0 g, K2HPO4 0.5 g, KNO3 1.0 g, MgSO4 1.0 g, FeSO4 0.02 g, glucose 1.0 g, peptone 0.5 g, tryptone 0.3 g and agar 20.0 g in 1.0 l distilled water (pH 8.0) at 4 °C. The stock culture was inoculated into 250 ml Erlenmeyer flasks containing 50 ml of seed medium, which was the same modified Gause’s no.1 liquid medium as above, but no agar. The culture was incubated on a rotary shaker (180 r.p.m.) at 28 °C for 24 h. Fifty millilitres of the seed culture was transferred to a 5000 ml Erlenmeyer flask containing 1000 ml of the producing medium, which was the same as the seed medium. The fermentation was carried out at 28 °C for 48 h on a rotary shaker (180 r.p.m.).

Eighty liters of the fermentation broth was centrifuged at 4500 r.p.m. for 20 min, then, the supernatant was obtained and was extracted twice with 40 l of ethyl acetate each time. The organic layer was pooled and concentrated under reduced pressure at 37 °C to give yellow syrup (2.3 g). It was then separated by preparative thin layer chromatography on 10 × 10 cm plates (silica gel 60F254, Merck KGaA, Darmstadt, Germany) using CHCl3-MeOH, 65:35 (v/v) as the developing solvent. Under UV 365 nm, bands with light blue fluorescence at Rf =0.35 were scraped and then eluted with methanol to yield a semipurified sample (260 mg). After dissolved in 1 ml methanol, the sample was filtered through a 0.22 μm membrane and was further purified by HPLC on a shim-Pack PRC-ODS column (250 × 20 mm, Shimadzu Corp., Tokyo, Japan) with MeOH-H2O, 55:45 (v/v) at 2 ml min−1. Peak at Rt=26 min, showed UV absorbance at 247 and 314 nm detected by prominence diode array detector (SPD-M20A, Shimadzu), was collected and pooled to yield 10.4 mg of (1) as a white powder.

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