Chemical structures and biological activities of rhamnolipids produced by Pseudomonas aeruginosa B189 isolated from milk factory waste

The aim of this work was to study chemical structures and biological activities of rhamnolipids produced by Pseudomonas aeruginosa B189 isolated from milk factory waste. The culture produced two biosurfactants, a and b, which showed strong activity and were identified as l-rhamnopyranosyl-l-rhamnopyranosyl-β-hydroxydecanoyl-β-hydroxydecanoate or Rha-Rha-C₁₀-C₁₀ and l-rhamnopyranosyl-l-rhamnopyranosyl-β-hydroxydecanoyl-β-hydroxydodecanoate or Rha-Rha-C₁₀-C₁₂, respectively. Both compounds exhibited higher surfactant activities tested by the drop collapse test than several artificial surfactants such as SDS and Tween 80. Rhamnolipid a showed significant antiproliferative activity against human breast cancer cell line (MCF-7) at minimum inhibitory concentration (MIC) at 6.25 μg/mL while rhamnolipid b showed MIC against insect cell line C6/36 at 50 μg/mL.