A biosurfactant-producing novel bacterial strain isolated from vermicompost having multiple plant growth-promoting...

The nutrient-rich vermicompost which is used as manure for the growth and development of plants is rich in microbial flora. These microbes protect the plants against several infectious pathogenic microbes. As certain microbes are known to produce biosurfactants as metabolites, an investigation was carried out to isolate biosurfactant-producing bacterial strains from vermicompost with the efficient antifungal property. From the study, it was revealed that biosurfactant-producing bacterial strains are present in the vermicompost. A total of nine bacterial strains were isolated from the vermicompost. Among them, one most efficient biosurfactant-producing bacterial strains with antifungal properties have been screened. After molecular characterization of the isolated strain, it was revealed that the bacterial strain is Bacillus licheniformis strain SCV1. The strain produces 3.4 ± 0.1 g/L of crude biosurfactant, which when column purified yields 3.1 ± 0.1 g/L of biosurfactant. The biosurfactant exhibited excellent emulsifying activity (E₂₄ ) of 96.56% against crude oil. The produced biosurfactant was identified as a lipopeptide consisting of a mixer of surfactin and iturin. Furthermore, the biosurfactant exhibited significant antifungal activity against a wide range of phytopathogens, showing 76.3% inhibition against Sclerotinia sclerotiorum, 53% inhibition against Colletotrichum gloeosporioides, 51% against Fusarium verticillioides, and 36% against Corynespora cassicolla. Along with antifungal activities, the stain was found to exhibit multiple plant growth-promoting traits. This study, thus indicates that vermicompost might contain biosurfactant-producing microbes which can render protection to the plant against various phytopathogens by the production of biosurfactants and can also stimulate plant growth.