Liquid-liquid separation of antibiotic with reverse micelles

Abstract

Antibiotics are normally produced in aqueous environments, which require further separation and purification steps. The steps are very important and consume a huge part of the overall production cost. Moreover, the production of antibiotics, which typically involves fermentation process, is usually capital intensive because large and complex fermentors and extensive equipment for multi-step downstream processing are required to handle large volume fermentation broths with a low product concentration (Lee et al., 2004). Thus, improvement of the separation and purification methods can make significant savings to the overall manufacturing costs. A range of separation methods such as conventional solvent extraction, ion-exchange, chromatography, crystallization, or a combination of these methods have been used for the recovery of antibiotics. In the separation of penicillin G from fermentation broth, a solvent extraction method has been used by industry for many years. If the antibiotic is a weak acid with a low pKa value, the pH used in the extraction should be lower than the pKa value to obtain the antibiotic in its free acid form (Gu, 2000). Nabais and Cardoso noted that the biggest concern in current solvent separation technique is the frequent formation of stable emulsions. These emulsions are difficult to be discarded with conventional techniques such as gravitation or centrifugation. These problems lead to other problems such as contamination of the final product, low extraction yield, high solvent losses and clogging of the equipment.