Submitted to: FEMS Microbiology Letters
Publication Type: Peer reviewed journal
Publication Acceptance Date: 3/13/2009
Publication Date: 4/6/2009
Citation: Rooney, A.P., Price, N.P., Ray, K.J., Kuo, T. 2009. Isolation and Characterization of Rhamnolipid-Producing Bacterial Strains from a Biodiesel Facility. FEMS Microbiological Letters. 295(1):82-87. Interpretive Summary: In this study, we found several new strains of rhamnolipid-producing bacteria, including from species not previously known to produce such compounds. Rhamnolipids are industrially useful compounds that are important for a variety of industries, most notably oil, cosmetics, detergents, pharmaceuticals and textiles. The new strains produce high amounts of rhamnolipids when grown on glycerol, which is predicted to increase in market availability with rise of biodiesel production. As such, these results will enhance our ability to produce value-added products using environmentally friendly, microbial-based processes.
Technical Abstract: Novel strains of rhamnolipid-producing bacteria were isolated from soils at a biodiesel facility on the basis of their ability to grow on glycerol as a sole carbon source. Strains were identified as Acinetobacter calcoaceticus, Enterobacter asburiae, E. hormaecheii, Pantoea stewartii and Pseudomonas aeruginosa. The strains of the former five species were found to produce rhamnolipids in quantities the same as, or similar to, co-isolated strains of P. aeruginosa. Measurements of surface tension revealed that that emulsifying properties of these strains were similar to levels displayed by rhamnolipids produced by P. aeruginosa. Results of MALDI-TOF mass spectrometry analyses revealed that the predominant compounds made by all strains were C10-C10 mono- and di-rhamnolipids. Notably, E. hormaechii and one strain of A. calcoaceticus produced rhamnolipids in amounts similar to the pseudomonads. As all strains examined were from the same taxonomic class of proteobacteria, further examination of species within this class may reveal many additional species previously not known to produce rhamnolipids as well as novel strains of already known rhamnolipid-producing taxa.