Biosurfactants and aqueous two-phase fermentation.

The partition of surfactants and a biosurfactant-producing microorganism was studied in polyethylene glycol and dextran aqueous two-phase systems. In the presence of sodium phosphate, surfactants distributed themselves according to charge. Cationic surfactants preferred the bottom phase, while anionic surfactants were attracted to the top phase. Increasing the phosphate molarity or the pH resulted in a more 1-sided surfactant partitioning. Biosurfactant partitioning was weaker than synthetic surfactant partitioning due to the weaker effective charge and lack to strong specific affinity for any of the phase-forming polymers. Bacillus Subtilis cells partitioned very strongly to the bottom phase. The bioscurfactant, surfactin, produced by this microorganism partitioned to the top phase. Batch fermentations were carried out in an aqueous 2-phase system. Surfactin was produced in larger quantities in the 2-phase fermentation than in the regular mineral salts medium.