A newly isolated indigenous strain BN10 identified as Pseudomonas aeruginosa was found to produce glycolipid (i.e., rhamnolipid-type) biosurfactants. Two representative rhamnolipidic fractions, RL-1 and RL-2, were separated on silica gel columns and their chemical structure was elucidated by a combination of nuclear magnetic resonance and mass spectroscopy. Subsequently, their cytotoxic effect on cancer cell lines HL-60, BV-173, SKW-3, and JMSU-1 was investigated. RL-1 was superior in terms of potency, causing 50 % inhibition of cellular viability at lower concentrations, as compared to RL-2. Furthermore, the results from fluorescent staining analysis demonstrated that RL-1 inhibited proliferation of BV-173 pre-B human leukemia cells by induction of apoptotic cell death. These findings suggest that RL-1 could be of potential for application in biomedicine as a new and promising therapeutic agent.

Aims:  To isolate a biosurfactant‐producing bacterial strain and to identify and characterize the chemical structure and properties of its biosurfactants. Methods and Results:  The bacterium Rhodococcus wratislaviensis BN38, isolated from soil, was found to produce glycolipid biosurfactants when grown on 2%n‐hexadecane. The glycolipids were isolated by chromatography on silica gel columns and their structures elucidated using a combination of multidimensional NMR and ESI‐MS/MS techniques. The main product was identified as 2,3,4,2′‐trehalose tetraester with molecular mass of 876 g mol−1. It was also noted that the biosurfactant was produced under nitrogen‐limiting conditions and could not be synthesized from water‐soluble substrates. The purified product showed extremely high surface‐active properties. Conclusions:  The glycolipid biosurfactant produced by the alkanothrophic strain R. wratislaviensis BN38 was characterized to be 2,3,4,2′‐trehalose tetraester which exhibited high surfactant activities. Significance and Impact of the Study:  Strain BN38 of R. wratislaviensis is a potential candidate for use in bioremediation applications or in biosurfactant exploration.

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