Biodegradability and toxicity of monorhamnolipid biosurfactant diastereomers

J Hazard Mater. 2019 Feb 15;364:600-607. doi: 10.1016/j.jhazmat.2018.10.050. Epub 2018 Nov 1.


Synthetic monorhamnolipids differ from biologically produced material because they are produced as single congeners, depending on the β-hydroxyalkanoic acid used during synthesis. Each congener is produced as one of four possible diastereomers resulting from two chiral centers at the carbinols of the lipid tails [(R,R), (R,S), (S,R) and (S,S)]. We compare the biodegradability (CO2 respirometry), acute toxicity (Microtox assay), embryo toxicity (Zebrafish assay), and cytotoxicity (xCELLigence and MTS assays) of synthetic rhamnosyl-β-hydroxydecanoyl-β-hydroxydecanoate (Rha-C10-C10) monorhamnolipids against biosynthesized monorhamnolipid mixtures (bio-mRL). All Rha-C10-C10 diastereomers and bio-mRL were inherently biodegradable ranging from 34 to 92% mineralized. The Microtox assay showed all Rha-C10-C10 diastereomers and bio-mRL are slightly toxic according to the US EPA ecotoxicity categories with 5 min EC50 values ranging from 39.6 to 87.5 μM. The zebrafish assay showed that of 22 developmental endpoints tested, only mortality was observed at 120 h post fertilization; all Rha-C10-C10 diastereomers and bio-mRL caused significant mortality at 640 μM, except the Rha-C10-C10 (R,R) which showed no developmental effects. xCELLigence and MTS showed IC50 values ranging from 103.4 to 191.1 μM for human lung cell line H1299 after 72 h exposure. These data provide key information regarding Rha-C10-C10 diastereomers that is pertinent when considering potential applications.

Keywords: Biodegradation; Biosurfactant; Rhamnolipid; Stereochemistry; Toxicity.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Animals
  • Biodegradation, Environmental
  • Cell Line
  • Embryo, Nonmammalian
  • Embryonic Development / drug effects
  • Glycolipids / chemistry
  • Glycolipids / metabolism
  • Glycolipids / toxicity*
  • Humans
  • Luminescent Measurements
  • Pseudomonas aeruginosa / metabolism
  • Stereoisomerism
  • Surface-Active Agents / chemistry
  • Surface-Active Agents / metabolism
  • Surface-Active Agents / toxicity*
  • Vibrionaceae / drug effects
  • Vibrionaceae / metabolism
  • Zebrafish


  • Glycolipids
  • Surface-Active Agents
  • rhamnolipid