| Cephalexin is an important and widely used semi-synthetic cephalosporin. Cephalosporins along with penicillins are beta-lactam antibiotics and they account for the majority of the antibiotic world market. Cephalexin is traditionally produced by a 10-step chemical synthesis. An enzymatic synthesis for Cephalexin has been developed, and offers several advantages over the classical route. The enzymatic synthesis reduces energy and solvent waste, but its use for industrial production has been limited due to the difficult separation. Liquid membranes, in particular supported liquid membranes (SLMs), are a promising solution to the separation. SLMs are not used commercially, as they are still plagued with instability. SLM with the additional modification of strip dispersion has been a recent development to solve this issue. This study describes work in which Cephalexin is separated from complex reaction mixtures encountered in the enzymatic synthesis using SLMs with strip dispersion.;SLMs with strip dispersion and carrier, Aliquat 336, were used for the recovery of Cephalexin from aqueous solutions. The separation of Cephalexin from single component solutions was first investigated. Key experimental parameters were indentified and Cephalexin recovery of over 99% has been achieved for most cases. In addition, the mass transfer resistances from the process were analyzed and the resistance from the extraction reaction between Cephalexin and Aliquat 336 was found to be dominant. Recovery of Cephalexin from non-ideal solutions was also investigated, which involved co-extraction from buffer anions and other components present in the enzymatic reaction mixture during Cephalexin synthesis. In situ extraction was also demonstrated in which Cephalexin was removed from enzymatic reaction mixtures as it was synthesized with the enzyme penicillin acylase, and resulted with an increase in Cephalexin yield compared to synthesis without in situ removal. Along with these promising results, the long-term stability, the availability of large scale hollow fiber modules, and the use of inexpensive and low vapor pressure solvents make the SLM with strip dispersion process suitable for commercial applications for recovery of antibiotics and other biochemicals. |
