PRODUCTION OF BIOSURFACTANT BIOSUR-PM BY PSEUDOMONAS-MALTOPHILA CSV89- CHARACTERIZATION AND ROLE IN HYDROCARBON UPTAKE

Pseudomonas maltophilia CSV89, a soil bacterium, produces an extracell ular biosurfactant, ''Biosur-Pm''. The partially purified product is n ondialyzable and chemically composed of 50% protein and 12-15% sugar, which indicates the complex nature of Biosur-Pm. It reduces the surfac e tension of water from 73 to 53 x 10(-3) N m(-1) and has a critical m icellar concentration of 80 mg/l. Compared to aliphatic hydrocarbons, Biosur-Pm shows good activity against aromatic hydrocarbons. The emuls ion formed is stable and does not require any metal ions for emulsific ation. The kinetics of Biosur-Pm production suggest that its synthesis isa growth-associated and pH-dependent process. At pH 7.0, cells prod uced more Biosur-Pm with less cell surface hydrophobicity. At pH 8.0, however, the cells produced less Biosur-Pm with more cell surface hydr ophobicity and showed a twofold higher affinity for aromatic hydrocarb ons compared to the cells grown at pH 7.0. The Biosur-Pm showed a pH-d ependent release, stimulated growth of the producer strain on mineral salts medium with 1-naphthoic acid when added externally, and facilita ted the conversion of salicylate to catechol. All these results sugges t that Biosur-Pm is probably a cell-wall component and helps in hydroc arbon assimilation/uptake.