Isolation, screening and improvement of rhamnolipid production by <em>Pseudomonas</em> isolates

611-619Rhamnolipids (RLs) have attracted attention of many scientists because of their low toxicity, biodegradability and ecological acceptability. Nevertheless,their use is extremely limited due to the high cost when compared with chemical surfactants.Therefore,in this studya total of twenty four Pseudomonas isolates were recovered from various soil samples. Screening for RLs production was done using Siegmund Wagner agar plates where six isolates appeared to produce RLs. Isolate P6 was chosen as the most promising RL producer and identified using 16S rRNA sequencing as P. aeruginosa. The best production of 2.5 g/L was obtained by isolate P6 after six days of incubation at 30°C, 250 rpm. Random mutagenesis using UV or gamma radiation resulted in improved RL production by the mutants, the best of which was designated 15GR, which produced RL at concentrations two times higher that of the parent isolate. Rhamnolipids from this mutant showed improved activity and higher emulsifying power relative to that of the parent. Therefore, P6 isolate and its mutant 15GR are promising RL producers which have the advantage of producing RLs from glucose without induction with hydrophobic carbon sources