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In this study, a novel lipopeptide antibiotic was isolated from the culture supernatant of Paenibacillus ehimensis strain MA2012. After analyses by mass spectrometry (MS), nuclear magnetic resonance (NMR), and high resolution mass spectrometry (HR-MS/MS) the compound was identified to be polypeptin C consisting of 3-hydroxy-4-methyl-hexanoic acid moiety and nine amino acids as peptide body. It has the same molecular mass (1115 Da) with that of polypeptin A and B but the amino acid positions differ. A relatively low concentration (125 ppm) of polypeptin C lowered the surface tension of water from 72.2 to 36.4 mN/m. It showed antimicrobial activity against several plant pathogenic bacteria and fungi. When the polypeptin C was applied to the ripe pepper fruits previously inoculated with conidia of Colletotrichum gloeosporioides, the hyphal growth on the fruit was significantly suppressed. Moreover, the hyphal morphology of C. gloeosporioides was greatly affected by the purified compound. All these data suggest the great potential of P. ehimensis MA2012 to control plant fungal and bacterial diseases.

BACKGROUND Bacillus velezensis and other Bacillus species are known for the production of bioactive secondary metabolites that are active against plant pathogenic fungi. In view of this, a study was undertaken to investigate the antifungal potential of B. velezensis AR1 culture supernatant. RESULT The butanol extract concentrate of B. velezensis AR1 was separated into different fractions by column chromatography. A fraction eluted by 9:1 chloroform: methanol caused 25.8–70.2% and 25.2–56.3% growth inhibition of Monilinia fructicola and Colletotricum goeosporioides, respectively. This fraction was subjected to solid‐phase extraction using a Strata SI‐1 column and further purified by prep‐TLC to obtain a pure metabolite showing a single peak on high performance liquid chromatography. On the basis of the nuclear magnetic resonance (NMR 1H, 13C, HH COSY, HSQC and HMBC) analysis, the metabolite was identified as 5‐N‐tyrosinylornithine. The compound exhibited antifungal activity against two plant pathogenic fungi. CONCLUSION 5‐N‐tyrosinylornithine, the secondary metabolite isolated from the culture supernatant of B. velezensis AR1 exhibited significant antifungal activity against two plant pathogenic fungi.

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