Structural and Physicochemical Characterization of Rhamnolipids produced by Pseudomonas aeruginosa P6

Abstract

Rhamnolipids are important biosurfactants for application in bioremediation, enhanced oil recovery, pharmaceutical, and detergent industry. In this study, rhamnolipids extracted from P. aeruginosa P6 were characterized to determine their potential fields of application. Thin-layer chromatographic analysis of the produced rhamnolipids indicated the production of two homologues: mono- and di-rhamnolipids, whose structures were verified by 1H and 13C nuclear magnetic resonance spectroscopy. Additionally, high performance liquid chromatography-mass spectrometry identified seven different rhamnolipid congeners, of which a significantly high proportion was di-rhamnolipids reaching 80.16%. Rha-Rha-C10-C10 was confirmed as the principal compound of the rhamnolipid mixture (24.30%). The rhamnolipids were capable of lowering surface tension of water to 36 mN/m at a critical micelle concentration of 0.2 g/L, and exhibited a great emulsifying activity (E24 = 63%). In addition, they showed excellent stability at pH ranges 4–8, NaCl concentrations up to 9% (w/v) and temperatures ranging from 20 to 100 °C and even after autoclaving. These results suggest that rhamnolipids, produced by P. aeruginosa P6 using the cheap substrate glycerol, are propitious for biotechnology use in extreme and complex environments, like oil reservoirs and hydrocarbon contaminated soil. Moreover, P. aeruginosa P6 may be considered, in its wild type form, as a promising industrial producer of di-RLs, which have superior characteristics for potential applications and offer outstanding commercial benefits.

Rhamnolipid Biosurfactant: Use for the Removal of Phenol from Aqueous Solutions by Micellar Solubilization

“…To determine the fractional composition in a mixture of mono- and di-RLs, it is necessary to compare the NMR signals of rhamnose and lipid groups in the 1 H or 13 C NMR spectra. The use of 1 H spectra for this purpose is difficult since the most informative line of methyl CH 3 protons of rhamnose overlaps with the line of methylene CH 2 protons of lipids. , However, in the 13 C NMR spectrum, the lines of methyl carbons are observed separately, for both lipids (δ = 14 ppm) and rhamnose groups (δ = 17 ppm) (Figure ).…”

“…The sample of the study is an unfractionated mixture of mono-RLs, di-RLS, and related products in the form of rhamnose residues and lipids. Analysis and identification of the structure and composition of RLs have been performed by chromatography methods, mass spectrometry, FT-IR spectroscopy, and NMR. − …”

Rhamnolipid Self-Aggregation in Aqueous Media: A Long Journey toward the Definition of Structure–Property Relationships

“…Rhamnolipids are typically produced by Pseudomonas aeruginosa [ 53 , 55 , 57 , 58 , 59 , 60 , 61 , 62 , 63 , 64 , 65 , 66 , 67 , 68 , 69 , 70 , 71 , 72 , 73 , 74 , 75 , 76 ], but they have also been isolated from other Pseudomonas bacteria [ 54 , 55 , 77 , 78 , 79 ], as well as from bacteria belonging to other families [ 80 , 81 , 82 , 83 , 84 ], classes [ 85 , 86 , 87 , 88 ], or even phyla [ 89 , 90 , 91 , 92 , 93 ]. In bacteria, rhamnolipids play many different physiological roles, including solubilization and uptake of hydrophobic nutrients, adhesion to surfaces, formation and maintenance of biofilms, and cell motility [ 55 , 94 , 95 , 96 , 97 , 98 ].…”

Adsorption Efficiency of Carbon Materials for the Removal of Organic Pollutants: DDT from Aqueous Solution

“…Additionally, they play a pivotal role in the remediation of oil, biobased heavy metals, and hydrocarbon pollutants. Given their cost-effectiveness, minimal toxicity, and environmentally benign properties, we have opted to utilize this biosurfactant. , …”