Identification of diacetonamine from soybean curd residue as a sporulation-inducing factor toward Bacillus spp.

摘要

Under bioassay-guided investigation, a sporulation-inducing factor (SIF) toward Bacillus spp. was searched for in methanol (MeOH) extracts of soybean curd residues, and diacetonamine (>1) was identified as the active compound. SIF was first isolated as a monoacetylated derivative (>2, 4.1 mg from 655 g soybean curd residues), and its chemical structure was elucidated by field desorption mass spectrometry, electron ionization mass spectrometry, and nuclear magnetic resonance (NMR) analyses. After 48-h incubation, 40 µM diacetonamine hydrochloride (>1b) exhibited sporulation-inducing activity with 35% sporulation frequency toward a Bacillus amyloliquefaciens wild-type strain (AHU 2170), whereas 40 µM diacetone acrylamide (>3) showed 99% sporulation induction, which was much higher than that of >1b. Although Bacillus megaterium NBRC 15308 was sporulated by the treatment with 400 µM >1b with 36 and 70% sporulation frequency after 72- and 96-h incubation respectively, >3 at the same concentration showed only 2% sporulation after 72-h incubation. Hence, diacetonamine (>1) was characterized as a genuine SIF from soybean curd residues, but it was uncertain whether >1 is a natural product or an artifact. Spores of B. amyloliquefaciens induced by >1b survived after treatment with heating at 95 °C for 10 min, also suggesting that >1 is genuine SIF in soybean curd residue. As sporulation induction is likely linked to activation of antibiotic production in some spore-forming Firmicutes bacteria, compound >1 would be a possible chemical tool to develop an effective fermentation technology in Bacillus species.Electronic supplementary materialThe online version of this article (doi:10.1186/s13568-017-0395-0) contains supplementary material, which is available to authorized users.