ACRYLAMIDE PRODUCTION IN AN ULTRAFILTRATION-MEMBRANE BIOREACTOR USINGCELLS OF BREVIBACTERIUM-IMPERIALIS CBS 489-74

Both differential and integral UF-membrane reactors were tested for th e bioconversion of acrylonitrile into acrylamide. Use was made of the commercially available flat membrane cell Amicon Mod,52 and the UF-mem branes FS81PP, GR81PP, and YM100, The enzymatic reaction was catalyzed by the nitrile hydratase (NHase) present in resting cells of Brevibac terium imperialis CBS 489-74, The system was operated at 4 degrees C a nd 10 degrees C. Acrylonitrile concentration ranged from 50 to 500 mM. The membrane resistance to chemicals was complete at acrylonitrile an d acrylamide concentrations up to 800 mM and 2 M, respectively. No rej ection of solute was determined. Membranes totally retained the restin g cells and no fouling was observed working with 2 and 16 mg of biocat alyst in stirred systems. Membrane compaction was apparently responsib le for roughly 35% flux loss during the first 3-4 h of operation. The laboratory scale membrane bioreactor, continuously operating, allowed to show the dependence of enzyme deactivation on acrylonitrile concent ration and process time. Substrate concentration higher than 100 mM we re highly detrimental for NHase stability. The acrylamide yield reache d in the multi-cycle process operating with 5.6 g/l of resting cells w as 93.7% and the product concentration during roughly 450 h of bioconv ersion attained 8.3% (w/v). Decay of specific membrane flux was 98% of the initial value. (C) 1998 Elsevier Science B.V. All rights reserved .