Before revision:  A model of optimal allocation of protein resources to achieve maximum growth quantitatively explains why and how the cell makes the choice when facing multiple carbon sources .
After revision:  A model of optimal allocation of protein resources to achieve maximum growth quantitatively explains why and how the cell makes the choice . In case of co-utilization, the model predicts the percentage of each carbon source in supplying the amino acid pools, which is quantitatively verified by experiments .