The bioconversion of 3cyanopyridine using the in situ nitrile hydratase–amidase cascade system of resting Microbacterium imperiale CBS 49874 cells was investigated in an ultrafiltrationmembrane reactor, operated in either batch or continuous mode. The effects of operating conditions such as the amount of biocatalyst, substrate concentration, substrate feeding rate, mean residence time, and enzymetosubstrate ratio, were investigated with the aim of achieving almost 100% substrate conversion and high reactor productivity. As a result, it was found that the NHase–AMase cascade system could be adequately exploited in a continuous reactor configuration. The differing temperature dependence of nitrile hydratase and amidase kinetics enabled the operational parameters to be module d to ensure (i) nitrile hydratase operational stability (at 5 ◦C), and (ii) 100% conversion of 3cyanopyridine into nicotinic acid, or, alternatively, (iii) enrichment of the effluent stream with the intermediate nicotinamide (up to 80% conversion). It was possible to select operating conditions that allowed long periods of operation (at least 100 h) at a constant flowrate without enzyme activity loss.
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