Efficient isolation of biosurfactant rhamnolipids from fermentation broth via aqueous two-phase extraction with 2-propanol/ammonium sulfate system

Abstract

The high production cost associated with environmentally unfriendly separation process significantly inhibit the real application of rhamnolipids in many fields. This study, for the first time, developed a green and efficient approach based on aqueous two-phase extraction by utilizing 2-propanol/(NH4)2SO4 to isolate rhamnolipids from the fermentation broth. After optimization, about 96% of the rhamnolipids were recovered from fermentation broth by employing aqueous two-phase extraction with 40% (v/v) 2-propanol and 200 g/L of (NH4)2SO4 at pH 5, with a purity of about 92%. Salts in the organic phase were then removed via re-generation of aqueous two-phase which resulted in a desalination ratio of over 95%. The present approach to extract rhamnolipids via aqueous two-phase extraction was also evaluated with fermentation broth produced by Pseudomonas aeruginosa PAO1 and 9027. This green and efficient separation process also enables the isolation of rhamnolipids from fermentation broth that cannot be precipitated under acidic conditions.