3-Cyanopyridine (3-cnp) modulates via inactivation and/or inhibition, the amidase activity of the resting cells of Microbacterium imperiale CBS 489-74 which contained an in situ nitrile hydratase-amidase (NHase/AMase) cascade system suitable for catalyzing the bio-production of nicotinic acid form 3-cnp. The combined effect of 3-cnp concentration and temperature is investigated on the sole AMase activity by selectively inactivating the NHase activity. The study was performed in continuous stirred membrane reactors (CSMRs) fed with 100 mM nicotinamide solutions containing 25-200 mM 3-cnp at various temperatures. At 25-40 degrees C, the inactivation constant is negligible, even at high 3-cnp concentration, and the decrease in AMase activity is reversible. At 50 degrees C, a synergistic effect of temperature and 3-cnp inactivates AMase irreversibly, thus preventing a high yield being reached. (c) 2012 Elsevier Ltd. All rights reserved.