ABSTRACT
Introduction ............................................................................................................ 147 Lipopeptide Biosurfactants .................................................................................... 148
Surfactin ............................................................................................................ 151 Surfactin Production .......................................................................................... 151
Lipopeptide Production Reactor Design and Optimization ................................... 154 Measurement and Characterization Techniques .................................................... 155 Genetics of Lipopeptide Production ...................................................................... 156 Extraction of Lipopeptides ..................................................................................... 157
Membrane Lipopeptide Recovery ..................................................................... 159 Strain Isolation ....................................................................................................... 160 Properties and Applications of Lipopeptides ......................................................... 164 Conclusion ............................................................................................................. 166 References .............................................................................................................. 167
Surfactants are classied as cationic, anionic, zwitterionic, and nonionic and are made synthetically from hydrocarbons, lignosulfonates, or triglycerides. Some common synthetic surfactants include linear alkyl benzenesulfonates, alcohol sulfates, alcohol ether sulfates, alcohol glyceryl ether sulfonates, α-olen sulfonates, alcohol ethoxylates, and alkylphenol ethoxylates (Layman, 1985). Surfactants have many applications industrially with multiphasic systems. Sodium dodecyl sulfate (SDS, C12H25-SO4− Na+) is a widely used anionic surfactant. The effectiveness of a surfactant is determined by surface tension lowering, which is a measure of the surface free energy per unit area or the work required to bring a molecule from the bulk phase to the surface (Rosen, 1978). These amphiphilic compounds (containing hydrophobic and hydrophilic portions) concentrate at solid-liquid, liquid-liquid, or vapor-liquid interfaces. An interfacial boundary exists between two immiscible phases. The hydrophobic portion concentrates at the surface while the hydrophilic is oriented toward the solution. A good surfactant can lower the surface tension of water from 72 to 35 mN/m and the interfacial tension (tension between nonpolar and polar liquids) for water against n-hexadecane from 40 to 1 mN/m. Efcient surfactants have a low CMC (i.e., less surfactant is necessary to decrease the surface tension) as the CMC is dened as the minimum concentration necessary to initiate micelle formation (Becher, 1965). In practice, the CMC is also the maximum concentration of surfactant monomers in water and is inuenced by pH, temperature, and ionic strength.
