A novel strategy to enhance the expression efficiency of cloned target gene in Escherichia coli was developed. The whole expression cartridge

consisting of promoter. SD sequence

target gene and transcription terminator

was tandem repeatedly engineered into a expression plasmid. Consequently

the copy number of specific gene was increased substantially

leading to the improvement of expression efficiency.Using this approach

a recombinant plasmid

designed as PLYD

was constructed and transformated into the Escherichia coli strain DH5α. Upon induction

the desired protein was synthesized in a considerable level and accumulated up to 63% of the total cell proteins. The present study revealed that tandem repeating of expression cartridge provided a convenient means to improve expression level efficiently.