The rhamnolipids will most likely be the next generation of biosurfactants to reach the market. They should follow closely after alkyl polyglycosides, already established in the biosurfactants market, and sophorolipids, which can be found in several cleaning agents. However, the greatest numbers of recent publications and patents among glycolipid biosurfactants have been dedicated to rhamnolipids. Produced mainly by Pseudomonas aeruginosa, rhamnolipids are mixtures of different rhamnolipid congeners, which show physico-chemical properties that differ from those of single congeners, with the most abundant structure in the mixture having the largest impact on the overall characteristics of the total mixture. Characteristics of biodegradability, low toxicity, production from renewable sources and antimicrobial (particularly antifungal) activity together make rhamnolipid biosurfactants particularly promising for broad commercial application. Although to date, bioremediation has been the major topic filed for patents utilizing rhamnolipids, the increasing number of patents for applications in cosmetics, agronomy and food industries, formulation of cleaners and nanotechnology indicates their future implementation in these fields.

The impact of the surface charge of alumina support on the adsorption of Candida rugosa lipase has been investigated in terms of zeta potential of the adsorption partners. Lipase adhered onto alumina with similar efficiency under both repulsive and attractive electrostatic conditions, shifting the zeta potential of the support towards that of the enzyme. The behavior was explained by a heterogeneous distribution of the surface charge of the lipase molecule. Special emphasis in this study was placed on the effect of immobilization on enzyme kinetics and principal reasons for enzyme immobilization: improvement in stability and potential for reuse. The enzyme affinity was not altered by its adsorption onto alumina, while Vmax of the lipase decreased. Thermostability of adsorbed lipase was improved. Significant potential for reuse was found. [Projekat Ministarstva nauke Republike Srbije, br. III 43004 i br. III 45012]

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

Enzymes produced by indigenous Pseudomonas aeruginosa strain have been subjected to research considering their potential application as detergent additives. As previously noted, lipase produced by Pseudomonas aeruginosa is highly alkaline, thermostable and solvent tolerant. Furthermore, same strain exhibits both lipase and protease activity establishing this lipase as potentially desirable component of enzyme-containing detergents. Further research was carried out to investigate insusceptibility of this lipase against coexisting native protease, several commercial surfactants, oxidizing agents and commercial detergents. Lipases and proteases remained highly active when incubated with several different surfactants and oxidizing agents under washing conditions. Moreover, presence of surfactants and oxidizing agents such as Tween® 20 and Triton® X-100 initially augment lipase and protease activity. Additionally, crude lipase preparation was insusceptible to coexisting native protease hence indicating possible storage stability. Overall, the remarkable properties of these enzymes make them potential detergent additives

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