Natural surfactants

The ever-increasing environmental concern about surfactants triggers an interest in natural surfactant. This review, which has an emphasis on work published since 1998, covers three categories of natural surfactants: amphiphiles produced by yeast or bacteria, amphiphiles containing a natural polar headgroup and amphiphiles containing a natural hydrophobic tail. Microorganisms produce both high molecular weight and low molecular weight surfactants. Only the low molecular weight compounds are included in the review. Sugars and amino acids are the two most important examples of surfactant polar headgroups of natural origin. The research is particularly intense in the area of sugar surfactants and the review covers three types: alkylglucosides, alkylglucamides and sugar esters. Surfactants based on two types of natural hydrophobic tails are included: fatty acid monoethanolamides and sterol ethoxylates. Routes of preparation as well as physico-chemical properties are discussed for the surfactants prepared by organic synthesis. (C) 2001 Elsevier Science Ltd. All rights reserved.