摘要：Biosurfactants are structurally diverse surface-active molecules, produced on living surfaces, mostly microbial cell surfaces or excreted extracellularly. Rhamnolipid biosurfactants have wide spectrum use and are predominantly produced by the bacteria P seudomonas aeruginosa . In this study, 75 Pseudomonas strains isolated from distinct native habitats were screened following oil spreading technique, methylene blue agar method, hemolytic blood agar method and surface tension measurement of the cell free culture. Ten selected isolates were tested for their ability to produce rhamnolipid biosurfactants in glycerol mediated broth. The best among them, Pa24, was confirmed as Pseudomonas aeruginosa through 16S rRNA sequence analysis. Experiments carried out on the ability of P. aeruginosa strain Pa24 revealed its potential to utilize range of vegetable oils such as coconut oil, palm oil, jatropha oil, neem oil and mineral glycerol as sole source of carbon and produce rhamnolipid biosurfactant. The extracted biosurfactant was characterized by thin layer chromatography and high performance thin layer chromatography as mixture of di-rhamnolipid and mono-rhamnolipid biosurfactants. The crude extract of rhamnolipid was tested in-vitro for antifungal activity against Phytophthora capsici and Phytophthora infestans and the MIC50 were found to be 815.8 ppm and 373.9 ppm, respectively. Further exploration on different renewable carbon sources including agriculture industrial wastes to produce rhamnolipid biosurfactants can improve the efficiency and reduce the environmental pollution through waste discharge from these industries
