Pseudomonas aeruginosa NCAIM(P), B001380, a propitious bacterial strain isolated from mineral cutting oil was identified to be chromium tolerant and a producer of biosurfactant rhamnolipid (RL) with potential application in heavy metal bioremediation. Culture growth, RL production and Cr(VI) removal capacity of the strain in the presence of 50 mg L-1 (I) and 100 mg L-1 of Cr(VI) (II) were studied. Maximum of RL production were found in the late-stationary phase at 72 h for both Cr(VI)-amended cultures: I (236 mg L-1) and II (160 mg L-1), as well as the maximum of Cr(VI) removal capacity: 70 % (I) and 57 % (II). The amount of Cr in RL preparation II was 22 mg mg-1 determined by flame atomic absorption spectroscopy (FAAS). Appearance of a new band at 914 cm-1 in infrared (IR) spectrum of RL (II) indicated a significant proof for possible coordination of CrO42-ion with RL. The effect of Cr(VI) on monorhamnolipids (RL1) and dirhamnolipids (RL2) distribution and its ratio were studied by electrospray ionization mass spectrometry (ESI-MS). An increase was observed in a RL2/RL1 ratio for II compared to control

Pseudomonas aeruginosa was repeatedly reported as powerful producer of rhamnolipid biosurfactants as well as producer of hydrolytic enzymes. In this study effects of four fermentation factors were evaluated using response surface methodology and experiments were performed in accordance with a four-factor and five-level central composite experimental design. Investigated factors were: fermentation temperature, time of fermentation, concentration of sunflower oil and concentration of Tween® 80. The most important finding was that regression coefficients of the highest values were those that describe interactions between factors and that they differ for lipase and rhamnolipid production, which were both investigated in this study. Production of both metabolites was optimized and response equations were obtained, making it possible to predict rhamnolipid concentration or lipase activity from known values of the four factors. The highest achieved rhamnolipid concentration and lipase activity were 138 mg dm-3 (sunflower oil concentration 0.8 %, Tween® 80 concentration 0.05 %, temperature 30°C, and fermentation time 72 h) and 11111 IU dm-3(sunflower concentration of 0.4 %, Tween® 80 concentration of 0.05 %, temperature of 30°C, and fermentation time of 120 h), respectively. [Projekat Ministarstva nauke Republike Srbije, br. E!6750 and br. III 46010