EVALUATION OF BIOSURFACTANT PRODUCING AND ANTIMICROBIAL RESISTANCE PSEUDOMONAS FOR HEAVY METALS TOLERANCE

This study aimed to evaluate biosurfactant production and antibiotic resistance in Pseudomonas bacteria isolated from some agricultural fields to detect the relationship of these isolates traits with some heavy metals resistance. Bacterial isolates were screened for biosurfactant production through blood hemolysis, oil spreading, emulsification activity, and surface tension. The antibiotic sensitivity was determined using disk diffusion method. Then, identification of the selected isolates and subjected to gradient concentrations of heavy metals to determine the minimum inhibitory concentration (MIC). Biosurfactant production was found in 74.29% of these isolates. The isolates resistance to Ticarcillin-clavulanate, Aztreonam, Piperacillin, and Imipenem were 92.86%, 31.43%, 2.86% and 1.43%, respectively. The eight selected isolates were identified by biochemical tests and VITEK 2 system as P. aeruginosa. The resistance of these isolates to heavy metals differed significantly. The isolate B49 recorded the highest resistance to Cu (MIC=3200 µg/ml) and Zn (MIC=2600 µg/ml), while the isolate B66 recorded the highest resistance to Cd (MIC=1000 µg/ml) and isolate B25 had higher resistance to Hg (MIC=80 µg/ml), and Pb (MIC=2800 µg/ml). The correlation coefficient between emulsification (E24%) and CdCl2 (r=0.27) and Pb (r=0.38) was significant positive, while E24% had a significant negative correlation with Zn (r= -0.63) and non-significant correlation to copper (r=0.02) and mercury (r=0.19) resistance

Oxidation of benzoin catalyzed by oxovanadium (IV) schiff base complexes

BACKGROUND: The oxidative transformation of benzoin to benzil has been accomplished by the use of a wide variety of reagents or catalysts and different reaction procedures. The conventional oxidizing agents yielded mainly benzaldehyde or/and benzoic acid and only a trace amount of benzil. The limits of practical utilization of these reagents involves the use of stoichiometric amounts of corrosive acids or toxic metallic reagents, which in turn produce undesirable waste materials and required high reaction temperatures. In recent years, vanadium complexes have attracted much attention for their potential utility as catalysts for various types of reactions. RESULTS: Active and selective catalytic systems of new unsymmetrical oxovanadium(IV) Schiff base complexes for the oxidation of benzoin is reported. The Schiff base ligands are derived between 2-aminoethanol and 2-hydroxy-1- naphthaldehyde (H2L1) or 3-ethoxy salicylaldehyde (H2L3); and 2-aminophenol and 3-ethoxysalicylaldehyde (H2L2) or 2-hydroxy-1-naphthaldehyde (H2L4). The unsymmetrical Schiff bases behave as tridentate dibasic ONO donor ligands. Reaction of these Schiff base ligands with oxovanadyl sulphate afforded the mononuclear oxovanadium(IV) complexes (VIVOLx.H2O), which are characterized by various physico-chemical techniques. The catalytic oxidation activities of these complexes for benzoin were evaluated using H2O2 as an oxidant. The best reaction conditions are obtained by considering the effect of solvent, reaction time and temperature. Under the optimized reaction conditions, VOL4 catalyst showed high conversion (>99%) with excellent selectivity to benzil (~100%) in a shorter reaction time compared to the other catalysts considered. CONCLUSION: Four tridentate ONO type Schiff base ligands were synthesized. Complexation of these ligands with vanadyl(IV) sulphate leads to the formation of new oxovanadium(IV) complexes of type VIVOL.H2O. Elemental analyses and spectral data of the free ligands and their oxovanadium(IV) complexes were found to be in good agreement with their structures, indicating high purity of all the compounds. Oxovanadium complexes were screened for the oxidation of benzoin to benzil using H2O2 as oxidant. The effect of time, solvent and temperature were optimized to obtain maximum yield. The catalytic activity results demonstrate that these catalytic systems are both highly active and selective for the oxidation of benzoin under mild reaction conditions.Web of Scienc