Lipopeptide biosurfactant from Bacillus thuringiensis pak2310: A potential antagonist against Fusarium oxysporum

Objectives. - The aims of the study were to evaluate the effects of a biosurfactant obtained from a novel Bacillus thuringiensis on Fusarium oxysporum to determine the morphological changes in the structure of the fungi and its biofilm in the presence of the biosurfactant and to evaluate the toxicity of the biosurfactant on HEp-2 human epithelial cell tines. Materials and methods. - The strain was screened and isolated from petroleum contaminated soil based on the E-24 emulsification index. The biosurfactant was produced on glycerol, extracted using chloroform:methanol system and purified using HPLC. The purified fraction showing both surface activity (emulsification and oil-spread activity) and anti-fusarial activity (agar well diffusion method) was studied using FT-IR and MALDI-TOF MS, respectively. The minimum inhibitory concentration (MIC) and the biofilm inhibitory concentration (BIC) were determined using dilution method. The effect of biosurfactant on the morphology of Fusarium oxysporum was monitored using light microscopy and confocal laser scanning microscopy (for biofilm). Results. - The purified surfactant showed the presence of functional groups like that of surfactin in the FT-IR spectra and MALDI-TOF MS estimated the molecular weight as 700 Da. The MIC and BIC were estimated to be 0.05 and 0.5 mg/mL, respectively. The molecule was also non-toxic to HEp-2 cell lines at 10 x MIC. Conclusion. - A non-toxic and effective anti-Fusarium biosurfactant, that is both safe for human use and to the environment, has been characterized. The growth and metabolite production using glycerol (major byproduct of biodiesel and soap industries) also adds up to the efficiency and ecofriendly nature of this biosurfactant. (C) 2014 Elsevier Masson SAS. All rights reserved.