The ultrafiltration of fermentation broths of demethylchlortetracycline (DM
CT) produced at an industrial scale at CIPAN SA, has been carried out, usin
g two ultrafiltration systems of different module geometries: a tubular mod
ule (B1 from Paterson Candy International Ltd.) and a plate-and-frame modul
e (LabStak M20 from Danish Separation Systems). A PVDF and a fluoro polymer
ultrafiltration membranes both with a MWCO of 100 KD were used. Although t
he highest permeate fluxes were obtained with plate-and-frame geometry, ser
ious problems arose in cleaning the whole system, due to accumulation of so
lids inside the module as the broths under study are not homogeneous and co
ntain oil-mycelium aggregates of macroscopic dimensions that cover a wide r
ange of particle size (fi-om less than 100 mum to about 2 mm). The results
obtained for the ultrafiltration operation are also compared with those obt
ained for the industrial filtration using rotary vacuum filters. The same y
ields 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 sol
ids. A rejection to demethylchlortetracycline related products (namely the
undesirable isomer epi-DMCT) by the two membranes under study higher than t
hat to DMCT is observed as well. (C) 2001 Elsevier Science B.V. All rights
reserved.