Apoptotic potential of biosurfactant (rhamnolipid) isolated from endophytic <i>Bacillus safensis</i> subsp. <i>safensis</i> FO-36b (T) MTCC 25740 against leukaemia cells

This study reports the isolation and characterisation of a biosurfactant-producing endophytic strain, <i>Bacillus safensis</i> subsp. <i>safensis</i> FO-36b (T) MTCC 25740 (RSS2), from <i>Phyllanthus niruri</i> L. Among 52 screened endophytes, RSS2 was the most potent biosurfactant producer, yielding rhamnolipid congeners predominantly comprising dirhamnolipids (RhaRhaC₁₀C₁₀). The purified biosurfactant exhibited a critical micelle concentration of 0.79 mg/mL and was structurally confirmed by HPLC, LC-MS, FTIR, and NMR. Cytotoxicity against Jurkat (T lymphoblast) cells showed a dose-dependent response (IC₅₀: 356.63 µM), with non-significant effects on normal PBMCs. Apoptosis analysis revealed 22.6% early and 73.2% late apoptosis respectively in leukaemia cells after 24 h, confirming selective pro-apoptotic activity. These findings highlight the potential of <i>B. safensis</i> derived rhamnolipids as natural, apoptosis-inducing anticancer agents. The study explores the promising role of biosurfactants in therapeutic development, and advocates future research on production optimisation, mechanistic insights into anticancer action, and the development of targeted biomedical formulations.