Lipopeptide iturin C 3 biosurfactant produced by endophytic Bacillus sp. LLB-04 effectively controls the colonization of topical and food-borne pathogens in vitro and on biomedical devices

The present study elucidates the structure and antimicrobial efficacy of a derivative of iturin biosurfactant (BS) produced by the endophytic bacterium Bacillus sp. LLB-04 (GenBank Ac No.: MF037706). The biosurfactant was produced in a static batch culture of 120 hours in an NB medium and was extracted by a series of solvent systems. The BS was purified by solvent fractionation and preparative HPLC method and characterized through GC-MS, ESI-MS, LC-MS qTOF and ¹ H NMR analysis. Its antimicrobial and antibiofilm activity was tested against topical and food-borne pathogens age-dependently. Furthermore, the cellular aggregation and bacterial cell adhesion on polystyrene and urethral catheters were checked at the BIC concentration. The cell line toxicity was tested against the human alveolar epithelial cancer cell line, and the in silico mode of action was studied using standard methods. The BS was harvested from 96 hr culture using a methanol-ethanol solvent. The spectroscopic studies revealed that Bacillus sp. LLB-04 produced the BS as iturin C ₃ . The BS has broad-spectrum antimicrobial with MIC values ranging from 0.1 to 1.6 mg/ml and an average BIC of 0.8 mg/ml in 18 hrs old cells. It could also destabilize 40–48 hrs old preformed biofilm and had a synergistic response with conventional antibiotics. It had antiproliferative activity (0.1 to 0.8 mg/ml) on cancer cell lines. In-silico protein-ligand interactions predicted that it could interact with different membrane proteins of topical and food-borne pathogens. Thus, the study revealed for the first time that the endophytic Bacillus sp. could be exploited for large-scale production of potent lipopeptide BS iturin C ₃ that could be used in combating topical and food-borne pathogens.