Rhamnolipids production by multi-metal-resistant and plant-growth-promoting rhizobacteria

Appl Biochem Biotechnol. 2013 Jul;170(5):1038-56. doi: 10.1007/s12010-013-0244-9. Epub 2013 May 3.

Abstract

The biosurfactant-producing Pseudomonas aeruginosa A11, with plant-growth-promoting (PGP) and multi-metal-resistant (MMR) features was isolated from the rhizosphere of a wild plant Parthenium hysterophorus. The strain A11 was able to utilize glycerol as a carbon source and produce 4,436.9 mg/L of biosurfactant after 120 h of incubation. The biosurfactants was characterized as rhamnolipids (RLs) by thin layer chromatography, Fourier transform infrared spectroscopy, nuclear magnetic resonance, and liquid chromatography-mass spectrometry analysis. Eight different RLs congeners were detected with RhaRhaC₁₀C₁₀ being most abundant. The purified rhamnolipid, dirhamnolipid, and monorhamnolipid reduced the surface tension of water to 29, 36, and 42 mN/m with critical micelle concentration of 83, 125, and 150 mg/L, respectively. The strain A11 demonstrated resistance against all the metals detected in rhizosphere except Hg and Ni. The strain A11 also possessed plant-growth-promoting features like siderophores, hydrogen cyanide, catalase, ammonia production, and phosphate solubilization. The dirhamnolipids formed crystals upon incubation at 4 °C, thus making separation of dirhamnolipids easy. Biosurfactant-producing ability along with MMR and PGP traits of the strain A11 makes it a potential candidate for application in the bacterial assisted enhancement of phytoremediation of heavy-metal-contaminated sites.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Asteraceae / drug effects
  • Asteraceae / growth & development*
  • Asteraceae / microbiology*
  • Glycolipids / biosynthesis*
  • Glycolipids / chemistry
  • Glycolipids / isolation & purification
  • Metals / pharmacokinetics*
  • Metals / pharmacology
  • Plant Roots / drug effects
  • Plant Roots / growth & development*
  • Plant Roots / microbiology*
  • Pseudomonas aeruginosa / isolation & purification
  • Pseudomonas aeruginosa / physiology*

Substances

  • Glycolipids
  • Metals
  • rhamnolipid