The rhamnolipids produced by Pseudomonas aeruginosa strains are often a mixture of several homologues. Up to seven (R2C10C10 + R1C10C10 + R2C10C12 + R1C10C12 + R1C12:1C10 + R1C12:2 + R1C8:2 ) have been identified in cultures of P. aeruginosa AT10 from soybean oil refinery wastes. This study deals with the production, purification, and identification of rhamnolipids in the mixture (M7), as well as their physical and chemical characterization and the evaluation of their antimicrobial properties. The surface tension decreases to 26.8 mN/m and the critical micelle concentration value to 1.2 × 102 mg/L. These molecules show excellent antifungal properties against Aspergillus niger and Gliocadium virens (16 μg/mL) and C. globosum, P. crysogenum , and A. pullulans (32 μg/mL), whereas the growth of the phytopathogenic fungi B. Cinerea and R. solani was inhibited at 18 μg/mL.

Abstract:Pseudomonas aeruginosa 47T2, grown in submerged culture with waste frying oil as a carbon source, produced a mixture of rhamnolipids with surface activity. Up to 11 rhamnolipid homologs (Rha-Rha-C 8 -C 10 ; Rha-C 10 -C 8 /Rha-C 8 -C 10 ;Rha-Rha-C 8 -C 12:1 ; Rha-Rha-C 10 -C 10 ; Rha-Rha-C 10 -C 12:1 ; Rha-C 10 -C 10 ; Rha-Rha-C 10 -C 12 /RhaRha-C 12 -C 10 ; Rha-C 10 -C 12:1 /Rha-C 12:1 -C 10 ; Rha-Rha-C 12:1 -C 12 ; Rha-Rha-C 10 -C 14:1 ; Rha-C 10 -C 12 /Rha-C 12 -C 10 ) were isolated from cultures of P. aeruginosa 47T2 from waste frying oil and identified by HPLC-MS analysis. This article deals with the production, isolation, and chemical characterization of the rhamnolipid mixture RL 47T2 . The physicochemical and biological properties of RL 47T2 as a new product were also studied. Its surface tension decreased to 32.8 mN/m; and the interfacial tension against kerosene to 1 mN/m. The critical micellar concentration for RL 47T2 was 108.8 mg/mL. The product showed excellent antimicrobial properties. Antimicrobial activity was evaluated according to the minimum inhibitory concentration (MIC), the lowest concentration of an antimicrobial agent that inhibits development of visible microbial growth. Low MIC values were found for bacteria Serratia marcescens (4 µg/mL), Enterobacter aerogenes (8 µg/ mL), Klebsiella pneumoniae (0.5 µg/mL), Staphylococcus aureus and Staphylococcus epidermidis (32 µg/mL), Bacillus subtilis (16 µg/mL), and phytopathogenic fungal species: Chaetonium globosum (64 µg/mL), Penicillium funiculosum (16 µg/mL), Gliocadium virens (32 µg/mL) and Fusarium solani (75 µg/mL).

The value of amino acids and vegetable oil derivatives as raw materials for the preparation of surfactants was recognized as soon as they were discovered early in the last century. Amino acid-based surfactants, which have an amino acid residue as a hydrophilic moiety, are reviewed with respect to their synthesis, properties and some applications. The review covers three main categories of amino acid-based surfactants: N a -acyl, N-alkyl amide and O-alkyl ester derivatives among the linear or single chain amino acid-based surfactants; N a , N w -bis(N a -acylarginine)a,w-alkylendiamides, which are gemini amino acid-based surfactants; and 1-monoacyl-rac-glycero-3-O-(N a -acetyl-L-amino acid) and 1,2-diacyl-rac-glycero-3-O-(N a -acetyl-L-amino acid), both amino acid-based surfactants with glycerolipid-like structures.Scheme 1 Structures of amino acid-based surfactants: (1) Linear or single chain, (2) Dimeric or Gemini and (3) Glycerolipid-like structures. The amino acid constitutes the polar head of the surfactant. The hydrocarbon alkyl chain constitutes the hydrophobic moiety.2 3 3 G r e e n C h e m . , 2 0 0 4 , 6 , 2 3 3 -2 4 0

The rapid increase of drug resistant bacteria makes necessary the development of new antimicrobial agents. Synthetic amino acid-based surfactants constitute a promising alternative to conventional antimicrobial compounds given that they can be prepared from renewable raw materials. In this review, we discuss the structural features that promote antimicrobial activity of amino acid-based surfactants. Monocatenary, dicatenary and gemini surfactants that contain different amino acids on the polar head and show activity against bacteria are revised. The synthesis and basic physico-chemical properties have also been included.