Cloning and Expression ofα-Amylase Gene inEscherichia coli: Effect on Specific Oxygen Uptake Rate and Host Cell Morphology during Batch Fermentation

Abstract

Cloning and expression of any heterologous gene product always impart metabolic load on the recombinant host for utilization of its metabolites that results in variations in cellular physiology. An understanding of such stress is important for robust process design and scaleup. In the present communication, an attempt has been made to explain the metabolic load imposed on the recombinant strain of Escherichia coli BL21(DE3) owing to over-expression of amyE gene, using different expression vectors of varying size. Current studies show that metabolic quotient or specific oxygen uptake rate (SOUR) of different recombinant hosts increases with an increase in vector size, showing correlation between vector size and cellular metabolic load. Further increase in SOUR on protein expression shows even higher metabolic load for protein expression than plasmid maintenance. Increase in bacterial size and decrease in specific growth rate on transformation and recombinant protein expression are cellular responses to additional metabolic load.