Effect of post-induction substrate oscillation on recombinant alkaline phosphatase production expressed in Escherichia coli

Microorganisms are exposed to fast changes in microenvironment in large scale bioreactors. Because of their fast response to the changes, overall performance of biological system in small scale differs from large scale. Hence the variations in the environment that microorganisms are living in are mimicked in small scale. For this purpose one way is to feed substrate into the bioreactor in an oscillatory profile. In this work two different types of triangular oscillatory feeding profiles were applied as the post induction feeding strategy in intracellular recombinant alkaline phosphatase production expressed in Escherichia coli to find out if this biological system behaves in inhomogeneous environment differently. On line and offline measurements provide evaluation of product quality and quantity. Then the results of the experiments were compared with those of the control run at which constant feeding rate was executed. The results showed that oscillatory feeding at which cells were not starved led to higher yield of protein per substrate (0.027 C-mol/C-mol) and higher activity per protein (0.79 U/mg) when compared to a constant feeding rate (0.011 C-mol/C-mol and 0.11 U/mg).