In fed-batch fermentation, mass of substrate utilized is calculated using the relationship

• initial mass of substrate in the reactor + final mass of substrate in the reactor + flow rate x [substrate in the feed]
• initial mass of substrate in the reactor - final mass of substrate in the reactor + flow rate x [substrate in the feed]
• initial mass of substrate in the reactor + final mass of substrate in the reactor - flow rate x [substrate in the feed]
• initial mass of substrate in the reactor + final mass of substrate in the reactor - flow rate