Biosurfactants, Rhamnolipids, Pseudomonas putidaObservation of both tensio-active and emulsifying activities indicated that biosurfactants were produced by the newly isolated and promising strain Pseudomonas putida 21BN. The biosurfactants were identified as rhamnolipids, the amphiphilic surface-active glycolipids usually secreted by Pseudomonas spp. Their production was observed when the strain was grown on soluble substrates, such as glucose or on poorly soluble substrates, such as hexadecane, reaching values of 1.2 g l
Ð1. When grown on hexadecane as the sole carbon source the biosurfactant lowered the surface tension of the medium to 29 mN m Ð1 and formed stable and compact emulsions with emulsifying activity of 69%.
A new strain Renibacterium salmoninarum 27BN was isolated for its capacity to utilize nhexadecane as sole substrate. Growth on n-hexadecane was accompanied with the production of glycolipid surface active substances detected by surface pressure lowering and emulsifying activity. Glycolipid detection by thin layer chromatography and infrared spectra analyses showed for the first time that Renibacterium salmoninarum 27BN secretes the two rhamnolipids RLL and RRLL typical for Pseudomonas aeruginosa. Growth of Renibacterium salmoninarum 27BN on n-hexadecane depended on the bioavailability of the substrate and the secreted rhamnolipids appeared to be efficient in increasing hexadecane availability for the cells.
Biosurfactant activity and naphthalene degradation by a new strain identified as Bacillus cereus 28BN were studied. The strain grew well and produced effective biosurfactants in the presence of n-alkanes, naphthalene, crude oil and vegetable oils. The biosurfactants were detected by the surface tension lowering of the medium, thin layer chromatography and infrared spectra analysis. With (2%) naphthalene as the sole carbon source, high levels of rhamnolipids at a concentration of 2.3 g l Ð1 were determined in the stationary growth. After 20 d of incubation 72 ð 4% of the initial naphthalene was degraded. This is the first report for a Bacillus cereus rhamnolipid producing strain that utilized naphthalene under aerobic conditions. The strain looks promising for application in environmental technologies.
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