White Biotechnology in Polymeric Biosurfactants

In contrary to the other surface active molecules, polymeric biosurfactants are high-molecular weight compounds and generally exhibit high emulsifying activity. Among current polymeric biosurfactants, a more potent one is emulsan. 

Emulsan is amphiphilic microbial lipopolysaccharide with covalendy attached fatty acids, mainly produced by Acinetobacter calcoaceticus, secreted as scaffold material for capsular polysaccharides. It is a high-molecular weight biopolymer consisting of amino sugars (D-galactosamine) and D-galactosaminouronic acid groups (F ure 14.13).  

The peculiar features ofemulsan are its excellent surface activity and emulsifying activity even at low concentration. Emulsan is secreted to medium as emulsan—protein complex where protein is covalently attached. Emulsan-protein complex has higher emulsification activity than the apoemulsan, which is emulsan devoid of protein. Emulsan exhibit Newtonian flow behavior and undergoes a conformational transition at oil—water interfaces.  

Candida lipolytica or Yarroma lipolytica produce a water-soluble biopolymer composed of 83% polysaccharide and 17% protein, which is called liposan. Liposan is usually produced by fermentation of medium containing hydrophobic substrates such as hexadec-ane. Liposan exhibits high emulsifying activity and emulsion stabilizing properties. Because of its inert nature, liposan can be used as smokable tobacco substitutes.  

Due to substrate specificity and low productivity of liposan, a thorough media engineering and novel fermenter design are required to develop a cost-effective technology for liposan production. Thiamine is very important nutrient for Y. lipolytica fermentation for liposan production. Pinchuk et al., proposed a self cycling fermenter with 

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