Influence of L-amino acids on the cell growth and protein expression of eshcerichia coli W3110

Abstract

The influences of L-amino acids on the cell growth and protein expression were investigated through the cultivation of E. coli W3110 in the media containing L-amino acids of various compositions and concentrations. In the media with 20 L-amino acids of 0.03g/L concentration before the exhaustion of 20 L-amino acids, the specific growth rate of cell, $0.906h^{-1}$, was higher than that in the minimal media without L-amino acids, $0.6h^{-1}$. But after the exhaustion of added L-amino acids, the specific growth rate, $0.492h^{-1}$, was lower than that in the minimal media, $0.6h^{-1}$. The optimal cell yield per unit glucose, 0.488 g/g, was obtained when 20 L-amino acids of 0.03g/L concentration were supplemented to the minimal media. This cell yield value was higher than that in the minimal without 20 L-amino acids, 0.445g/g. This demonstrates that considerable amounts of compounds serve as the carbon source. Also this value was higher than those in the abundant media containing 0.05g/L and 0.1g/L 20 L-amino acids, 0.450g/g and 0.402g/g, respectively. This result was obtained because the acetate was produced more in the media with more 20 L-amino acids. Among 20 L-amino acids, the only glycine could improve the specific growth rate of cell. When 20 L-amino acids mixture of 0.03g/L concentration were supplemented to the minimal media, R/2 media containing glucose, the specific growth rate between 3hour and 4hour suddenly decreased. The exhaustion of glycine had the most effect on this phenomenon. L-valine inhibited the cell growth by obstructing the synthesis of L-isoleucine. When L-valine above 0.00005 g/L was added individually, the time of lag phase was lengthened. But after a certain period, the cell growth (growth rate, $Y_{X/S}$, and $Y_{ace/X}$) was similar with that in the media without L-valine. In other words the cell growth could be restored by itself. The more L-valine was added, the longer the time of lag phase was. But at the concentration above 0...