The rhamnoside lipid surfactant is a kind of bio-metabolic bio-surfactant produced by Pseudomonas or Burkholderia species. It is currently the most intensively studied and has the broadest application prospects among all bio-surfactants. It possesses excellent chemical and biological properties, is amphiphilic in oil and water, can reduce the surface tension of water, and can be used as a wetting agent, emulsifier and foaming agent. This bio-surfactant can be used under extreme conditions of temperature, pH value and salinity, and is non-toxic and biodegradable.

Physical and chemical properties: 

(1) The molecular weight of rhamnolipid is usually between 476 and 766 g/mol. 

(2) The critical micelle concentration is between 20 and 200 mg/L.

 (3) The HLB value of rhamnolipid has not been reported in relevant literature. According to the usual calculation method, through the analysis of functional influence, its HLB value is between 10 and 15. 

(4) It can reduce the surface tension of water from 72 mN/m to 30 mN/m. The interfacial tension between oil and water can be reduced from 43 mN/m to 1 mN/m. 

(5) Thermal stability: It can still maintain its surface activity at a high temperature of 90℃. 

(6) Salt resistance: It does not precipitate or dissolve in a 10% salt solution, while synthetic surfactants will lose their activity in a 2-3% salt solution. 

(7) Biodegradability: It is easily degraded in water bodies or soil biological environments.

 (8) Low toxicity or non-toxic, friendly to the environment.