Adsorption of certain betalactam antibiotics on activated carbonpolymeric resins equilibrium and kinetic studies

Abstract

Well known for their broad antibacterial activity, the B-lactam antibiotics par-ticularly the penicillins and cephalosporins constitute a large portion of the multimillion dollar antibiotic market. Since discovery of penicillins by Fleming1 and cephalosporins by Newton and Abraham2, processes for production of natural and semisynthetic penicil-lins and cephalosporins have undergone various modifications. Most of the commercially important natural B-lactams are produced by biochemical processes. The semisynthetic penicillins and cephalosporins can be prepared by chemical or enzymatic process, the latter having potential advantages in several respects. The growing interest in various B-lactam antibiotics over the past decade has called upon improvement of their production methods via modification of either the basic process or microbial strain or downstream processing techniques. Recovery of B-lactams from the usually dilute product of bioreactor is important for both analytical and prepara-tive purposes. The product recovery may involve various methods of extraction and puri-fication which play an important role in the overall process economics3,4. However, al-most all the known processes for commercial scale extraction and purification are based on low yielding operation because of the unfavourable physical properties of the B-lactams, particularly the cephalosporins. While the less hydrophilic penicillins can be re-covered by the well known solvent extraction technique, difficulties arise in case of cephalosporins, which are highly hydrophilic possessing zwitterionic properties. Adsorption chromatography, recommended for extraction and purification of various hydrophilic biproducts5 can be competitive for B-lactams particularly the cepha-losporin group of antibiotics. The adsorbents known from patent literature5,6 are activated carbon, molecular sieves and non-ionic / ion-exchange resins. Though much work has been done to improve the separation of cephalosporins by analytical liquid chromatogra-phy, preparative...