Uranium binding by emulsan and emulsanosols

Emulsan, the extracellular bioemulsifier of Acinetobacter RAG‐1, bound up to 0.9 μm of uranium per 1 mg emulsan. The dissociation constant for the emulsan‐uranium complex, K appI was 1.2 × 10⁻⁴M. Much larger amounts of uranium were bound to emulsan when the biopolymer occurred on hexadecane‐water interfaces. Under these conditions, more than 3.5 µm uranium were bound per 1 mg emulsan and the dissociation constant K appII was 5.1 × 10⁻⁵M. At pH 2, more than 90% of the uranium bound to emulsan on the hexadecane‐water interface was desorbed, while less than 10% bioemulsifier was released from the interface. The different binding parameters of emulsan when free in solution and while adsorbed onto the hexadecane water interface are discussed in view of potential applications and as a model system for studying the properties of an extracellular amphipathic polymer bound to a hydrophobic surface.