Exploration of surfactin production by newly isolated Bacillus and Lysinibacillus strains from food-related sources

As a lipopeptide (LP), surfactin exhibits properties, such as emulsifying and dispersing ability, which are useful in food industry. Discovery of new LP-producing strains from food sources is an important step towards possible application of surfactin in foods. A total of 211 spore-forming, Gram-positive, and catalase-positive bacterial strains were isolated from fermented African locust beans (iru) and palm oil mill effluents in a screening process and examined for their ability to produce surfactin. This was achieved by a combination of methods, which included microbiological and molecular classification of strains, along with chemical analysis of surfactin production. Altogether, 29 isolates, positive for oil spreading and emulsification assays, were further identified with 16S rDNA analysis. The strains belonged to nine species including less commonly reported strains of Lysinibacillus, Bacillus flexus, B. tequilensis, and B. aryabhattai. The surfactin production was quantitatively and qualitatively analysed by high-performance thin-layer chromatography and liquid chromatography-mass spectrometry (LC–MS). Confirmation of surfactin by MS was achieved in all the 29 strains. Highest surfactin production capability was found in B. subtilis IRB2-A1 with a titre of 1444·1 mg L⁻¹.