Ultrafiltration of demethylchlortetracycline industrial fermentation broths

Abstract

Abstract The ultrafiltration of fermentation broths of demethylchlortetracycline (DMCT) produced at an industrial scale at CIPAN SA, has been carried out, using two ultrafiltration systems of different module geometries: a tubular module (B1 from Paterson Candy International Ltd.) and a plate-and-frame module (LabStak M20 from Danish Separation Systems). A PVDF and a fluoro polymer ultrafiltration membranes both with a MWCO of 100 KD were used. Although the highest permeate fluxes were obtained with plate-and-frame geometry, serious problems arose in cleaning the whole system, due to accumulation of solids inside the module as the broths under study are not homogeneous and contain oil–mycelium aggregates of macroscopic dimensions that cover a wide range of particle size (from less than 100 μm to about 2 mm). The results obtained for the ultrafiltration operation are also compared with those obtained for the industrial filtration using rotary vacuum filters. The same yields are achieved for about the same dilution, but ultrafiltration has the advantage of not requiring filter aid and flocculants as the conventional filtration process does. The filtrate quality is also another advantage of the membrane process, as the permeates are completely free of suspended solids. A rejection to demethylchlortetracycline related products (namely the undesirable isomer epi -DMCT) by the two membranes under study higher than that to DMCT is observed as well.