Kawal: A fermented food as a source of Bacillus strain producing antimicrobial peptides

Abstract

Kawal is a fermented food condiment obtained by spontaneous fermentation of Senna obtusifolia leaves. Fermentative microbiota's consists of microorganisms producing a diversity of bioactive molecules. Thus, research of novel microbial products capable of inhibiting or eliminating plant and food pathogens is an absolute necessity. In this study, 126 bacterial strains were isolated from Kawal. Phenotypical, biochemical and genotypic methods were used to determine their genus or species. Forty-three (43) of them belonging to the genus Bacillus were selected for their antibacterial and antifungal properties. Their ability to produce lipopeptides (fengycins, surfactins, iturins, kurstakins) was investigated using HPLC and Matrix-assisted Laser Desorption Ionization-Time of Flight (MALDI-ToF-MS). Molecular characterization of 16S rRNA identified 10 species belonging to the genus Bacillus: B. subtilis, B. licheniformis, B. amyloliquefaciens, B. velezensis, B. spizizenii, B. wiedmannii, B. tropicus, B. cereus, B. tequilensis and B. safensis. MALDI-ToF-MS analysis revealed a diversity of antimicrobial molecules. Among all Bacillus strains tested, 84.44% produced surfactin, 22.22% produced fengycin, 11.11% produced iturin and 2.22% produced kurstakin. The results of this study demonstrated the high diversity of lipopeptides among kawal Bacillus strains and their antimicrobial capacity. In view of the potentialities that have been highlighted in these strains, some of them can be used in the bioconservation or in the bioprotection of plants.