Biodegradability and toxicity of monorhamnolipid biosurfactant diastereomers

David E. Hogan, Fei Tian, Scott W. Malm, Christopher Olivares, Ricardo Palos Pacheco, Michael T. Simonich, Anoop S. Hunjan, Robert L. Tanguay, Walter Klimecki, Robin L Polt, Jeanne E Pemberton, Joan E Curry, Raina Margaret Maier

Research output: Contribution to journalArticle

3 Scopus citations

Abstract

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.

Original languageEnglish (US)
Pages (from-to)600-607
Number of pages8
JournalJournal of Hazardous Materials
Volume364
DOIs
StatePublished - Feb 15 2019

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Keywords

  • Biodegradation
  • Biosurfactant
  • Rhamnolipid
  • Stereochemistry
  • Toxicity

ASJC Scopus subject areas

  • Environmental Engineering
  • Environmental Chemistry
  • Waste Management and Disposal
  • Pollution
  • Health, Toxicology and Mutagenesis

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