Gravimetric feed control uses a weight-based measurement to create an efficient method of controlling the flow of liquids into a bioreactor. Bioreactor feed control with balances can be easily achieved by accurately measuring weight to obtain a consistent and reproducible fermentation. This application note describes how METTLER TOLEDO balances can be used to control the amount of liquids pumped into a bioreactor by following a simple bioreactor loop control process between the bioreactor, the pump and the balance. It also explains how to select the right balance and which types of balances are typically used for gravimetric feed control.