A packed bed reactor (PBR) is ideal for product-inhibited immobilised enzyme reactions because it exhibits plug flow behaviour — substrate concentration is highest at the inlet (reactor entry) and lowest at the outlet. This means the enzyme near the inlet operates under high substrate, low product conditions (high activity); only the enzyme near the outlet is exposed to inhibitory product concentrations. In a CSTR, the entire reactor operates at the low exit concentration, maximising inhibition throughout.