Kannurin, a novel lipopeptide from Bacillus cereus strain AK1: isolation, structural evaluation and antifungal activities

Abstract

This study was performed to isolate and characterize novel antifungal lipopeptide from Bacillus cereus. Elucidation of its chemical structure was carried out by electrospray ionization mass spectra (ESI-MS) and Fourier transform infrared spectroscopy (FT-IR). The compound is a cyclic heptapeptide and composed of amino acids, Leu-Asp-Val-Leu-Leu-Leu-Leu. The in vitro activity of Kannurin against various pathogenic yeasts was assessed by CLSI M27-A and moulds by M38-A. It demonstrated broad-spectrum, fungicidal activity against clinically relevant yeasts and moulds. Kannurin exhibited low haemolytic activity and remained active over a wide pH and temperature range. In addition, Kannurin did not bind with melanin particles and was as active in inhibiting biofilms. An antifungal surfactin-like lipopeptide produced by Bacillus cereus strain AK1 was purified and chemically characterized. We propose to name this lipopeptide compound 'Kannurin'. To our knowledge, this is the first report of Bacillus cereus producing surfactin-like lipopeptide antibiotic with stronger antifungal activity. Our results provide a valuable contribution towards a better understanding of the lipopeptide of Bacillus cereus. Moreover, it raises the possibility of using as an alternative antibiotic in clinical medicine.