ABSTRACT
This chapter deals with the different possibilities of biosurfactant production, which are often dependent on the synthesized substances. It also deals with the product recovery and represents different methods of biosurfactant isolation as extraction by solvents, precipitation, in situ extraction, adsorption, flotation, and reactive extraction. The main problem in the hydrocarbon degradation by microorganisms is the water insolubility of these substrates. Another striking phenomenon is the catabolite repression of biosurfactant synthesis by glucose and other primary metabolites. The biosynthesis of biosurfactants by growing cells is often connected with foam formation, a lowering of the surface and interfacial tension of the medium, and an emulsion of the lipophilic substrate in the culture broth. While growing cells were forming only two rhamnolipids, four rhamnolipids could be isolated from the culture broth of resting cells, containing two new, more hydrophilic compounds. Rhamnolipid production by resting cells could be increased evidently in comparison with growing cells under N-limitation.
