Separation And Skin Penetration Of Rhamnolipid For Application In Cosmetics

Rhamnolipids,a kind of anionic biosurfactant,have ecological features including low skin stimulus,low toxicity and strong biodegradability,etc.Being of not only desired surface activities including washing,emulsifying and permeating but also of good bioactivity such as antibacterial,anti-wrinkle,they can be used as ingredients in cosmetic industry.Nevertheless,the diverse impurities in rhamnolipid fermentation broth are difficult to be separated from,largely limiting its use in cosmetic industry.This thesis investigated the efficient separation/purification of rhamnolipids with a low toxicity for matching the requirements of cosmetic products.Furthermore,the effect of rhamnolipid surfactant on skin penetration was studied.Firstly,the compositions of the fermentation broth except for rhamnolipids were classified and analyzed.The main impurities consisted of fatty acids,nitrogen-containing substance(pigments)and proteins,with each accounting to over 20%.The residue impurities were sterols,glycerides,polysaccharides,alginate,and heterocyclic polyols etc.Secondly,two separation methods were applied in this thesis.The traditional separations comprising inorganic/organic membrane and adsorption by resin were applied for rhamnolipid isolation.In this method,bacterium,protein,major odor molecules and pigments were removed from fermentation and rhamnolipids with purity more than 80%were obtained.Nevertheless,the recovery rate was only 46.9%,limiting its application in industrial treatment.The novel separation of rhamnolipids by calcium precipitation was proposed by ourselves.In this method,Ca2+was used to precipitate rhamnolipids and some impurities,followed by the dissolution by ethanol,and then reduced by hydrochloric acid.Finally,rhamnolipids with a purity of more than 95%and the recovery rate of 77.6%were obtained.Finally,anionic fluorescent surfactants which contain fluorescein as fluorescence group,-COONa as hydrophilic group and long carbon chain(12/16/18C)as hydrophobic group were synthesized.The CMC of each fluorescent surfactant was below 100mg/L while the surface tension could be reduced under 40-50mN/m.The fluorescent surfactant could penetrate into cells and skins,well reflecting the permeation property of rhamnolipids.It was found that the small molecule lacking surface activity could quickly penetrate into the skin layer in presence of rhamnolipid.Above all,the recovery rate of traditional separations was top low and the purity of the product was not satisfied.While the calcium precipitation method,one of the major innovation in this study,was effective enough.This method has lots of advantages including low toxicity,high recovery rate,low cost and could be applied for industrial amplification,laying a solid foundation for the use of rhamnolipids in cosmetic industry.The other innovative point is about the synthesis of fluorescent surfactant and its application for tracing cell/skin penetration.This will benefit the research on skin penetration of surfactants.