Synthesis, Characterisation and Properties of Novel Biosurfactants Based on Hydrophobically-Modified Inulins

A series of alkenylated inulin samples have been synthesized in aqueous solution using alkenyl succinic anhydrides with varying alkenyl chain lengths (C8-C18). The inulin derivatives (ASA-inulins) have been characterized using FTIR, MALDI-TOF MS and NMR and their degree of substitution determined. The solution properties of the ASA-inulins have been investigated using dye solubilisation, surface tension and dynamic light scattering techniques and it was confirmed that the molecules aggregated in solution above a critical concentration (critical aggregation concentration, CAC). The value of the CAC was in reasonable agreement using the three techniques and it was noted that it decreased with increasing degree of substitution and increasing alkenyl chain length. It has been demonstrated that the derivatives show surface activity and can stabilize foams, their effectiveness has been compared to the commercially available surfactants SDS and Tween 20. The functional properties were shown to be a function of the size of inulin used and the length of the alkenyl chains having a smaller secondary effect.