Immobilised lactase is used to hydrolyse lactose in dairy waste to glucose and galactose. Enzyme is immobilised in resin particles and packed into a 0.5 m3 column. The total effectiveness factor for the system is close to unity; Km for the immobilised enzyme is 1.32 kg m-3; Vmax is 45 kg m-3 h-1. The lactose concentration in the feed stream is 9.5 kg m-3; a substrate conversion of 98% is required. The column is operated with plug flow for a total of 310 d per year. At what flow rate should the reactor be operated?

• A. 1.56 m3 h-1
• B. 1.58 m3 h-1
• C. 1.50 m3 h-1
• D. 1.54 m3 h-1